Regulations (Preambles to Final Rules) - Table of Contents Regulations (Preambles to Final Rules) - Table of Contents
• Record Type: Occupational Exposure to Lead (November 1978)
• Section: 3
• Title: Section 3 - III. Executive Summary

III. EXECUTIVE SUMMARY

The following is a summary of the health effects, permissible exposure limit, medical removal protection, and feasibility sections of the final standard. A brief description of OSHA's decisions in the final standard and their rational is set forth in this summary. A more detailed discussion of each of these sections appears as Attachments A-D.

A. HEALTH EFFECTS

The record demonstrates that lead has profoundly adverse effects on the health of workers in the lead industry. Inhalation, the most important source of lead intake, and ingestion result in damage to the nervous, urinary, and reproductive systems and inhibit synthesis of the molecule heme, which is responsible for oxygen transport in living systems. The adverse health effects associated with exposure to lead range from acute, relatively mild, perhaps reversible stages such as inhabitation of enzyme activity, reduction in motor nerve conduction velocity, behavioral changes, and mild central nervous systems (CNS) symptoms, to permanent damage to the body, chronic disease, and death.

The signs and symptoms of severe lead intoxication which occur at blood lead levels of 80 ug/100 g and above are well documented. The symptoms of severe lead intoxication are known from studies carried out many years ago and include loss of appetite, metallic taste in the mouth, constipation, nausea, pallor, excessive tiredness, weakness, insomnia, headache, nervous irritability, muscle and joint pains, fine tremors, numbness, dizziness, hyperactivity, and colic. In lead colic, there may be severe abdominal pain, such that abdominal surgery mistakenly has occasionally been performed.

Damage to the central nervous system in general and the brain (encephalopathy) in particular is the most severe clinical form of lead intoxication. The most severe, often fatal, form of encephalopathy may be preceded by vomiting, apathy progressing to drowsiness and stupor, poor memory, restlessness, irritability, tremor, and convulsions. It may arise precipitously with the onset of intractable seizures, followed by coma, cardiorespiratory arrest and death. There is a tendency toward the occurrence of weakness of extensor muscle groups, that is motor impairment. This weakness may progress to palsy, often observed as a characteristic "wrist drop" or "foot drop" and is a manifestation of a disease to the peripheral nervous system (peripheral neuropathy). Lead intoxication also results in kidney damage with few, if any, symptoms appearing until extensive and most likely permanent kidney damage has occurred. NIOSH testified that:

Of considerable concern are the effects resulting from long-term lead exposure. There is evidence that prolonged exposure can increase the risk of nephritis, mental deficiency, premature aging, and high blood pressure(Ex. 84. p. 6).

Exposure to lead results in decreased libido, impotence and sterility in men and decreased fertility, abnormal menstrual and ovarian cycles in women. The course of pregnancy is adversely affected by exposure to lead. There is conclusive evidence of miscarriage and stillbirth in women who were exposed to lead or whose husbands were exposed. Children born of parents either of whom were exposed to lead are more likely to have birth defects, mental retardation, behavioral disorders or die during the first year of childhood.

During the past 10 years there have been many new observations and research on the health effects of lead at levels heretofore thought to be inconsequential. This research has been stimulated by the availability of many new methods for detecting and measuring the degree of impairment caused by lead exposure. These techniques measure a variety of biochemical, physiological and psychological disturbances. The methods are highly sensitive and reveal earlier changes indicative of adverse effects in workers exposed to lead.

The main research topics which have been addressed are early biochemical changes in the synthesis of the respiratory pigment heme; and early effects on the nervous system including behavioral and peripheral nerve effects. Included are studies on the involvement of lead in kidney disease, on effects on reproductive capacity of male and female workers, and on the relation between exposure to lead in air and resulting blood lead concentration.

Although the toxicity of lead has been known for 2,000 years the complex relationship between lead exposure and human response is still imperfectly understood. OSHA believes that while incapacitating illness and death represent one extreme of a spectrum of responses, other biological effects such as metabolic or physiological changes are precursors or sentinels of disease which should be prevented. This disease process can be subdivided according to Bridbord (Tr. 1976-02) into five stages: normal, physiological change of uncertain significance, pathophysiological change, overt symptoms (morbidity), and mortality. Within this process there is no sharp distinction, but rather there is a continuum of effects. Boundaries between categories overlap due to the variation of individual susceptibilities and exposures in the working population. OSHA believes that the standard adopted must prevent pathophysiologic changes from exposure to lead. Pathophysiologic changes indicate the occurrence of important health effects. Rather than revealing beginnings of illness the standard must be selected to prevent an earlier point of measurable change in the state of health which is the first significant indicator of possibly more severe ill health in the future. The basis for this decision is twofold -- first, pathophysiologic changes are early stages in the disease process which would grow worse with continued exposure and which may include early effects which even at early stages are irreversible, and therefore represent material impairment themselves. Secondly, prevention of pathophysiologic changes will prevent the onset of the more serious, irreversible and debilitating manifestations of disease.

The evidence in this record demonstrates that prevention of adverse health effects from exposure to lead throughout a working lifetime requires that blood (PbB) lead levels be maintained at or below 40 ug/100 g. OSHA concludes that workers exposed to lead leading to blood lead levels in excess of 40 ug/100 g will develop physiological and pathophysiological changes which will grow progressively worse and increase the risk of more severe disease. OSHA believes the standard must prevent these changes from occurring since this would provide greater assurances of health protection. Feasibility constraints prevent OSHA from establishing a standard which would eliminate all physiological changes, reproductive effects or mild signs and symptoms but the agency believes the vast majority of workers will be protected by this standard. These considerations formed the basis upon which OSHA evaluated the health effects evidence in the record. The remainder of this summary will address the health effects evidence in each system: heme synthesis inhibition, and damage to the nervous, urinary, and reproductive systems. In addition, the air lead to blood lead relationship will be addressed.

1. "Heme Synthesis Inhibition." Heme is a complex molecule which has two functions in the body. First, heme is a constituent of hemoglobin, a protein present in red blood cells whose primary function is to transport oxygen to the tissues. Interference with the formation of heme, if sufficient, results in decreased hemoglobin and ultimately anemia. Anemia is characterized by weakness, pallor and fatigability as a result of decreased oxygen carrying capacity in the blood.

Heme is also a constituent of another group of extremely important proteins, the cytochromes, which are present in every cell of the body. The function of heme in the cytochromes is to allow the cell to utilize oxygen. Heme may therefore be described as the "respiratory pigment" for the entire body. Interference with heme formation leads to interference in the respiration of every cell in the body. This is the most important effect of heme synthesis impairment. Piomelli has suggested that heme impairment in the cells would lead to a condition in each cell similar to that which would occur if the lungs of an individual did not function well. The central nervous system is particularly sensitive to the lack of oxygen and neurological damage could conceivably occur prior to anemia as a result of heme synthesis impairment in the brain. For example, Piomelli testified that "It is very well known that the human being cannot stop breathing for more than 2 or 3 minutes without developing irreversible brain damage." (TR. 460) This effect would be expected to occur from impaired respiration resulting from impaired heme synthesis. In other words, heme synthesis impairment could potentially affect every cell through reduced respiration.

The effects of lead exposure on heme synthesis have been studied extensively by the scientific community. Nevertheless, there is considerable debate over certain issues concerning the health effects of lead on this system. The Agency found three major issues particularly important in evaluating the health effects of lead in reference to heme synthesis.

(1) What is the meaning of the enzyme inhibition and physiological changes known to occur in this system at low lead levels, and should these effects be considered as per se impairment of health in the establishment of a permissible level of worker exposure to lead. (2) At what blood lead (PbB) level does a lowering of hemoglobin leading to anemia begin to occur? (3) To what extent are lead effects on heme synthesis in the blood forming system indicative of changes in heme synthesis in other tissues? The earliest demonstrated effect of lead involves its ability to inhibit the formation of heme. Scientific evidence has established that lead inhibits at least two enzymes of the heme synthesis pathway at very low PbB levels. Inhibition of delta aminolevulinic acid dehydrogenase (ALAD), an enzyme responsible for the synthesis of a precursor to heme, is observed at PbB levels below 20 ug/100 g. At a PbB level of 40 ug/100 g more than 20 percent of the population would have 70 percent inhibition of ALA-D. In the human body when an enzyme system is inhibited two effects are often seen: First, the molecule upon which the enzyme would act accumulates because it cannot undergo chemical reaction to produce the desired product and second, the desired product therefore decreases. Significant urinary excretion of the products of ALAD inhibition, such as delta aminolevulinic acid (ALA), occurs at this PbB level; 11 percent of adult males are excreting more than 10 ug/L.

The build-up of another product of impairment indicating inhibition of another enzyme, ferrochelatase, also occurs at low PbB levels. At a PbB level of 50 ug/100 g a larger proportion of the population would suffer these effects and the effects would be more extreme. At a PbB level of 50 ug/100 g, 70 percent of the population would have 70 percent inhibition of ALA-D, 37 percent would have urinary ALA (ALA-U) values larger than 10 ug/l and 80 percent of men and 100 percent of women would have increased free erythrocyte protoporphyrin (FEP), which is the product of inhibition of ferrochelatase. (Ex. 294 E.) Industry representatives argued that these effects are the manifestation of the body attempting to maintain a stable internal environment to lead. OSHA believes that it is inappropriate and simplistic to describe these changes as biochemical adjustments. The depression of heme synthesis in all cells of the body is an effect of potentially far reaching proportion and prevention of enzyme effects is the key to the prevention of more serious clinical effects of lead toxicity, which become more obvious as the exposure continues. These measurable effects are a direct result of lead exposure and are considered by the agency to indicate the occurrence of disruptions of a fundamental and vital subcellular process, heme synthesis. These processes are not only essential to the process of hemoglobin synthesis, they are also vital to the function of all cells since heme is ubiquitous in the human.

OSHA believes the evidence indicates a progression of health effects of lead exposure starting with inhibition of enzymes, continuing through effects indicating measurable disruption of subcellular processes, such as the buildup of the products of impaired heme synthesis and eventually developing into the overt symptoms of lead poisoning as manifested by disorders in the nervous, renal, and blood forming system. Biological variability among individuals will alter the PbB level at which a particular person will move through each stage in this disease continuum. Therefore, at each higher PbB level a greater proportion of the population will manifest each given effect. Given this understanding of the progressive stages of lead effects, OSHA has concluded that enzyme effects indicative of the disruption of heme synthesis are early stages of a disease process which eventually results in the clinical symptoms of lead poisoning. OSHA agrees with Piomelli who concluded, "It is the responsibility of preventive medicine to detect those alterations (in heme synthesis) which may precede frank symptomatology and to prevent the occurrence of these symptoms" (Tr. 456) OSHA believes that good health is not limited to the narrow definition of "absence of clinical symptoms." The early steps of the progression to disease cannot be considered as an attempt by the body to merely adjust and stabilize the internal environment to exposure to lead: They are early indications of significant physiological disruption. Whether or not the effects have proceeded to the later stages of clinical disease, disruption of these processes over a working lifetime must be considered as material impairment of health. As we previously discussed, at a PbB level of 40 ug/100 g and above, a significant proportion of the population would manifest extensive inhibition of ALA-D, elevations of ALA-U and of protoporphyrin levels. The agency believes that PbB levels should ideally be kept below 40 ug/100 g to minimize these effects.

Anemia is one of the established symptoms of lead poisoning. The symptoms of anemia are weakness, tiredness, pallor, waxy, sallow complexion, headache, irritability, and other symptoms characteristic of the increased load on the cardiac system. These clinical symptoms of anemia due to lead are often indistinguishable from those of chronic anemias with a variety of other causes. Anemia due to lead is often seen in association with acute abdominal colic. The occurrence of anemia, as a result of lead exposure, is known to occur above PbB levels of 80 ug/100 g. The occurrence of this symptom at PbB levels below 80 was debated during the hearings.

OSHA believes that the debate concerning the occurrence of this symptom can better be comprehended within the context of an understanding of the full disease process which eventually results in anemia. The evidence concerning the mechanisms of this disease process indicates that the effect of lead on the hematopoietic system is subtle and complex. In evaluating the disease mechanisms of anemia, it was found that lead is an insidious poison which attacks, not one, but many of the physiological processes within the cell.

Because anemia is the result of a complex of different lead effects, there is considerable room for individual variability in the PbB level at which anemia will occur. Hemoglobin level is a continuous variable which may cause individuals to have a problem to a greater or lesser degree at any particular blood lead level. Anemia should be viewed as a late step in a complicated progression of lead effects.

Since anemia is a consequence of lowered hemoglobin (the protein in red cells responsible for respiration) OSHA has carefully analyzed those studies which reported reduced hemoglobin. Studies have associated PbB levels as low as 50 ug/100 g with lowered hemoglobin (Hb) levels (Ex.6(37); 146-A; 5(9)). In particular, Tola's study, which showed a lowering of Hb over time during lead exposure of 50 ug/100 g, is considered by OSHA as an example of lead affecting Hb levels at this low PbB range. In addition studies by the Mt. Sinai group (Ex. 24(14)), and Wolfe (Ex. 146(A)) also demonstrated lowered anemia in lead exposed workers.

Based on evidence that indicates decreases in Hb levels with blood leads above 50 ug/100 g, OSHA has concluded that a lowering of Hb level to a measurable degree will occur at PbB levels as low as 50 ug/100 g. The degree to which Hb is lowered at this PbB range may be undetected since symptoms may be mild and are not likely to be so large as to require treatment for anemia. However, these changes must not be evaluated only as short-term effects alone but rather as changes that would occur over prolonged times. This implies that with reduced hemoglobin in an asymptomatic or mildly symptomatic individual there is a lifetime alteration in the oxygen carrying capacity of the blood, in the blood viscosity and in particular, in the cardiac work load. These alterations are distinct from the frank symptoms of anemia but are far more insidious and may be deleterious to the worker over the long term. Lastly, the data does support the view that lead induced anemia is clinically apparent at PbB's as low as 50 ug/100 ml.

In evaluating the effects of lead on heme synthesis, Piomelli suggested that hematopoietic effects such as anemia are not the most significant clinical effect of heme synthesis disruption * * *." A much more important fact is that the alteration of the mechanism of heme synthesis reflects the general toxicity of lead in the entire body. (Tr. 458)

Evidence indicates that there is disruption of heme synthesis in other tissues of the body besides blood, and that this disruption results in alteration of the oxygen transport into the cells of the body. Enzyme (ALA-D) inhibition due to lead exposure has been found in the liver at PbB levels below 40 ug/100 g (Ex. 5(22)). Electron microscope studies have revealed mitochondrial changes associated with lead exposure such as lead granules in rat liver mitochondria (Tr. 459, ref. Walton in Nature 243, 1973) and broken distorted mitochondria in the renal cells of a lead-exposed worker. The mitochondria is that portion of the cell responsible for extracting nutrients and oxygen and in turn providing the energy needed elsewhere in the cell for performing cellular functions. (Cramer et al. Brit. J. Ind. Med. 1974) Some of these studies related changes in heme synthesis in the blood forming tissues to changes in other tissues. Secchi (Ex. 5(22)) found a direct correlation of levels of ALA-D inhibition in the blood and in the liver. Millar found parallel decreases in ALA-D activity in the blood and in the brain at PbB levels above 30. (Ex. 23(68)), ref. Millar. This evidence supports Piomelli's suggestions that changes in heme synthesis in the blood forming (hematopoietic) system reflect changes that occur in other tissues. The work of Fishbein et al. related levels of products of enzyme inhibition, a measure of heme synthesis disruption in the hematopoietic system, to various signs and symptoms of lead exposure including central nervous system symptoms, muscle and joint pain, weight loss, and lead colic at blood lead levels well below 80 ug/100 ml (mean PbB was approximately 60 ug/100 ml). (Ex. 105D). Fishbein also noted anemia in 37 percent of these same workers, 17 percent of whom had blood lead levels below 60 ug/100 ml.

While the evidence relating lead effects of heme synthesis to symptoms throughout the body is not complete, the evidence is extensive enough and the issue is important enough to warrant very serious consideration with reference to the establishment of the standard. OSHA believes this evidence demonstrates that one early stage of lead disease in various tissues is the disruption of heme synthesis and that these effects in other lead-sensitive tissues parallel the measurable effects of heme synthesis disruption in the hematopoietic system and occur at comparably low PbB levels (below 40 ug/100 g). The heme effect is clearly not the only mechanism by which lead exerts its toxicological effect but it is one mechanism which we have substantial understanding of, can measure, and therefore must utilize in an effort to prevent the more severe symptoms in the individual.

In reference to the hematopoietic system, OSHA believes that the effects of lead are a complex progression from various biochemical changes through to the onset of clinical symptoms. At increasingly higher PbB levels an increasing proportion of the population will suffer more extreme effects. At a PbB level of 40 ug/100 g or above, a sizable proportion of the population would show measurable effects of the disruption of heme synthesis. A comparable degree of disruption of heme synthesis would most likely occur in other cells in the body.

Piomelli gave an excellent summary of the importance of lead's effects on heme synthesis stating:

It is my understanding that regulations have the purpose of preventing "material impairment of health." Alterations in heme synthesis do not produce subjective evidence of impairment of health, unless they reach the extreme depression in severe lead intoxication, when marked anemia occurs and the individual feels weak. However, it is not any longer possible to restrict the concept of health to the individuals subjective lack of feeling adverse effects. This is because we know that individuals may get adjusted to suboptimal health, if changes occur slowly enough and also because we now have the ability to detect functional impairments by appropriate tests, much before the individual can perceive any adverse effect. In fact, it is the responsibility of preventive medicine to detect those alterations which may precede frank symptomatology, and to prevent its occurrence. The alterations in heme synthesis caused by lead fulfill, in my opinion, the criteria for material adverse effects on health and can be used to forecast further damage. The depression of heme synthesis in all cells of the body is an effect of far reaching proportion and it is the key to the multiple clinical effects of lead toxicity, which become obvious as the exposure continues. (Ex. 57, p. 21).

This does not in any way suggest that the lead effect on heme is the only mechanism of lead disease, but it does suggest that this effect is at least one of the important mechanisms in lead disease. An understanding of this spectrum of effects from subcellular to clinical symptoms is relevant not only to the occurrence of anemia but will also be the expected pattern in lead induced neurological and renal disease.

OSHA believes that there is evidence demonstrating the impairment of heme synthesis and mitochondrial disruption in tissues throughout the body, and that these effects are the early stages of lead disease in these various tissues. The disruption of heme synthesis measured at low PbB levels is not only a measure of an early hematopoietic effect, it is also a measure which indicates early disease in other tissues. The Agency believes that such a pervasive physiological disruption must be considered as a material impairment of health and must be prevented. PbB levels greater than 40 ug/100 g should, therefore, be prevented to the extent feasible.

2. "Neurological effects." There is extensive evidence accumulated in both adults and children which indicates that toxic effects of lead have both central and peripheral nervous system manifestations. The effects of lead on the nervous system range from acute intoxication, coma, cardiorespiratory arrest and fatal brain damage to mild symptoms, subtle behavioral and electrophysiologic changes associated with lower level exposures. Although the severe effects of lead have been known for some time, only in the last several years has evidence accumulated which demonstrates neurologic damage at low blood lead levels. All of this data reinforces a disturbing clinical impression that nervous system damage from increased lead absorption occurs early in a worker's tenure, at low blood lead levels and is only partially reversible if at all. It is now understood that the location and degree of neurological damage depends on dose and duration of exposure.

The record in this rulemaking demonstrated that damage occurs in both the central and peripheral nervous systems at blood lead levels lower than previously recognized. In particular, Lilis et al. (Ex. 24. (10)) has demonstrated central nervous system symptoms (tiredness, fatigue, nervousness, sleeplessness or somnolency, or anxiety) in 56 percent of workers with blood lead levels below 80 ug/100 ml. The mean blood level was approximately 60 ug/100 ml. This same study reported symptoms of muscle and joint pain and/or soreness in 39 percent of the workers. It is extremely important to note that many of these subjects had been exposed less than a year. They also were able to demonstrate behavioral changes which were correlated with enzyme inhibition products from heme synthesis. Given this data, the authors cautioned that blood lead levels should not be allowed to exceed 60 ug/100 ml, and should be maintained around 40 ug/100 ml. Lilis testified that about 60 ug/100 ml, "one may expect florid lead poisoning, full blown lead-poisoning" (Tr. 2700). She proceeded to state:

"Since ZPP starts to go up at around levels of 40 or 45, that means that at those levels you already find something going wrong in the body" (TR. 2702). Repko has carried out behavioral tests and demonstrated adverse effects in visual reaction time, as well as deficits in hearing among workers having a mean blood lead level of 46 ug/100 ml. Valciukas et al. and Haenninen et al. have also demonstrated impaired psychological performance among workers with low exposure to lead. Haenninen's work is particularly significant insofar as no single blood lead concentration had ever exceeded 70 ug/100 ml.

Based on the rulemaking record, OSHA has concluded that the earliest stages of lead-induced central nervous system disease first manifest themselves in the form of behavioral disorders and CNS symptoms. These disorders have been documented in numerous sound scientific studies and these behavioral disorders have been confirmed in workers whose blood lead levels are below 80 ug/100 g. Given the severity and potential non-reversibility of central nervous system disease. OSHA must pursue a conservative course of action. OSHA concludes that a blood lead level of 40 ug/100 g must be considered to be a threshold level for behavioral changes and mild CNS symptoms in adults, and to protect against long-term neurological effects, blood levels should never exceed 60 ug/100 g.

Some of the most extensive evidence in the rulemaking record is the data presented which confirms the existence of the early stages of lead induced damage to the peripheral nervous system in workers exposed to lead levels below 70 ug/100 g. Damage to the peripheral nervous system is named peripheral neuropathy and the distinguishing feature of it is the predominance of motor involvement as opposed to sensory damage. Three forms are noted. In the first, patients with acute abdominal colic may also complain of very severe pain and tenderness in the trunk muscles, as well as pain in the muscles of the extremity. As the pain and tenderness subside, weakness may emerge, with very slow recovery over the ensuing several months. In the second, more common form of peripheral neuropathy due to lead poisoning, the neuropathy is described as painless, peripheral weakness occurring either after termination of excessive exposure or after long, moderately increased exposure. This suggests that neuropathy of sufficient severity may cause irreversible impairment of peripheral nerve function.

The third form is seen in subjects with no obvious clinical signs of lead poisoning and is manifested by a slowing of motor nerve conduction velocity. The latter effect represents the earliest sign of neurological disease of the peripheral nerves. OSHA believes prevention of this stage is necessary to prevent further development of the disease and its associated forms which are likely to be irreversible.

The work of Catton, Oh, Landigran, Feldman, Behse Mostafa et al., Gerald et al., Guadriglic et al., Araki, W. R. Lee, Repko, Lilis, Fischbein et al., and Seppalainen all demonstrate statistically significant loss of motor nerve conduction velocity in lead-exposed workers. Seppalainen was able to determine a dose-response relationship for the slowing of NCV compared with blood lead levels. It is apparent that slowing occurs in workers whose PbB levels are 50 ug/100 g and above but, whether there are effects as low as 40 ug/100 g is, as yet, undetermined. The 38 lead experts who participated in the Second International Workshop on Permissible Exposure Levels for Occupational Exposure to Inorganic Lead also reached this conclusion in their final report:

It is not known whether the maximum blood lead concentration or the integrated average concentration is the determining factor in the development of changes in nerve conduction velocity. However, the Group concluded from the data presented by Seppalainen et al. and the data reported in the literature that changes in nerve conduction velocity occur in some lead workers at blood levels exceeding 50 ug/100 ml. It was thought that no conclusion could be drawn from the one case in the blood lead range 40-49 ug/100 ml.

It is not possible to decide what any given measured small deficit means in terms of specific nervous damage. However, it is generally recognized that a clear deficit in the nerve conduction velocity of more than one nerve is an early stage in the development of clinically manifest neuropathy. There is no evidence that these changes progress. Reversibility should be studied. Although slight changes may be measured in persons experiencing no symptoms, it was the consensus of the group that such changes should be regarded as a critical effect. (Ex. 262, p. 64.) (Critical effect is a defined point in the relationship between dose and effect in the individual, namely the point at which an adverse effect occurs in cellular function of the critical organ.)

These conclusions by recognized experts in the field were based largely on the work of Seppalainen and her coworkers. This work has been described by an industry spokesman, Dr. Malcolm, as being "immaculate." (Tr. 2073) Based on the extensive evidence in the record from Seppalainen and others, OSHA has concluded that exposure to lead at low levels causes peripheral neuropathy at exposure levels previously thought to be relatively little consequence. Seppalainen has stated:

Of course, in terms of health, the importance of slight subclinical neuropathy can be questioned, too, and we did not find any evidence that the well-being of these workers was influenced by the neuropathy, apart from a few complaints of numbness of the arms. Thus, the term "poisoning," in its orthodox sense, cannot be applied to these disorders. But neuropathy, no matter how slight, must be regarded as a more serious effect than the quite reversible alterations in heme synthesis, because the nervous system has a poor regenerative capacity, and the acceptability of such a response must be judged from that point of view. Since the entire question belongs to the diffuse "gray area" between health and disease, it is more than probable that opinions will diverge. We think, however, that no damage to the nervous system should be accepted, and that, therefore, present concepts of safe and unsafe PbB levels must be reconsidered (Ex. 5(12), p. 183).

Recovery from the effects of chronic lead poisoning may be feasible in some cases, if the worker is removed from the source of exposure and therapy is initiated immediately. There are instances, however, when complete recovery is impossible and the pathology is fixed. Even if the worker is removed from the source and therapy initiated, the worker may still experience impairment. In a recent paper describing his results Dr. R. Baloh, a neurologist at UCLA, questioned the reversibility of nervous system damage:

Although there are isolated reports of significant improvement in lead-

induced motor neuron disease and peripheral neuropathy after treatment with chelation therapy, most studies have not been encouraging, and in the case of motor neuron disease, death has occurred despite adequate chelation therapy.

All of this data reinforces a disturbing clinical impression that nervous system damage from increased lead absorption is only partially reversible, if at all, with chelation therapy and/or removal from further exposure. This is not particularly surprising, however, since experience with other heavy metal intoxication has been similar. Nervous system damage from arsenic and mercury responds minimally to chelation therapy. Apparently, irreversible changes occur once the heavy metal is bound by nervous tissue. Although further study is clearly needed, the major point I would like to make this morning is that there is strong evidence to suggest the only reliable way to treat nervous system damage from increased lead absorption is to prevent its occurrence in the first place (Ex. 27(7), p. 55).

OSHA agrees with these concerns regarding irreversibility of neurological disease expressed by Dr. Baloh and therefore must establish a standard which will prevent the development of nervous system pathology at its earliest stages.

In order to prevent peripheral neuropathy as evidenced by slowing in NCV's Seppalainen testified that "to be safe, I would say 50 ug/100 g blood" is the necessary level (Tr. 147). Dr. Seppalainen further recommended that studies be performed to determine "the safety at the level of 50 ug/100 ml" (Tr. 153). OSHA agrees that the current evidence demonstrates that nerve conduction velocity reduction occurs at PbB levels of 50 ug/100 g and above. Therefore, a necessary goal of a standard for occupational lead exposure must be to assure that blood lead levels are maintained below 50 ug/100 g in order to provide an adequate margin of safety.

3. "Renal system." One of the most important contributions to the understanding of adverse health effects associated with exposure to inorganic lead was the elucidation of evidence on kidney disease during the hearings. It is apparent that kidney disease from exposure to lead is far more prevalent than previously believed. In the past, the number of lead workers with kidney disease in the United States was thought to be negligible, but the record indicates that a substantial number of workers may be afflicted with this disease. Wedeen, a nephrologist (kidney specialist), who testified at the hearings for OSHA stated that a minimal estimate of the incidence of this disease (nephropathy) would be 10 percent of lead workers. "According to this estimate, there may be 100,000 cases of preventable renal disease in this country. * * * If only 10 percent of these hundred thousand workers with occupational nephropathy came to chronic hemodialysis (kidney machines) the cost to medicare alone would be about 200 million dollars per year." (Tr. 1741-42) The hazard here is compounded by the fact that, unlike the hematopoietic system, routine screening is ineffective in the early diagnosis. Renal disease may be detected through routine screening only after about two-thirds of kidney function is lost or when manifestation of symptoms of renal failure are present. By the time lead nephropathy can be detected by usual clinical procedures, irreparable damage has most likely been sustained. When symptoms of renal failure are present, it is simply too late to correct or prevent the disease and "progression to death or dialysis is likely." (Tr. 1732.) The research of Wedeen and his co-workers, the health hazard evaluation by NIOSH at Eagle Picher Industries, Inc., and the research in secondary smelters by Lilis, Fishbein, et al. demonstrated that lead exposure is a key etiologic agent in the development of kidney disease among occupationally exposed workers. Clearly, too little attention has been given to lead-induced renal disease in recent years, and while OSHA recognizes that further research is required to understand fully the disease mechanism, it is also necessary to protect the thousands of workers who are potentially in danger of developing renal disease. The record indicates that blood lead is an inadequate indicator or renal disease development. Dr. Bridbord questioned Dr. Wedeen on the issue of chronicity of exposure and blood lead levels:

Dr. Bridboard: Well, looking at a group of workers, currently employed, having a blood lead level on that worker and having some information, that to the best of our knowledge there were no major changes in that particular plant during the past number of years. Would that not be a somewhat better index of what the blood lead levels might have been in the past. Considering too, that these workers are currently employed.

Dr. Wedeen: Sure I think that the blood level measured close to the time of exposure is probably more reflective. I worry very much, that this may occur after a few months of exposure and the blood lead level may remain the same for the next 20 years, despite the fact that the individual is continually accumulating lead in the body.

Dr. Bridbord: Would you think that the chronicity of lead exposure, apart from precisely whether the blood lead was above or below 80 or above or below 60 for example, might be an important factor in determining the eventual development of renal disease in lead workers? Dr. Wedeen: Yes; that is just what I meant, that the accumulative effects and the cumulative body burden may be very different from the blood lead level at any moment in time.

In other words, one could certainly imagine that a blood lead level of 80, for two years, may be very similar to a blood lead level of 40, for four years. I don't have that data, but something like that may well exist in terms of the danger of the different levels of exposure.

Dr. Bridbord: Alright. Particularly, in view of that, and given the requirements of the Occupational Safety and Health Act, that sets standards which protect during the working lifetime. Would you have some reservations about a blood lead maximum standard, even at 60? Dr. Wedeen: I certainly would. And I think I just expressed the basis for it. You will note that in my recording of these patients, very very few of them had blood lead levels over 60. I just feel that while the blood lead level is maybe better than nothing, it may be very practical. It probably doesn't do the job we are trying to do and certainly not from the physician's point of view, who has seen the individual patient, who may or may not be a current exposure at the level that got his disease (Tr. 1765-1766).

The lead standard must therefore be directed towards limiting exposure so that occupational lead nephropathy is prevented. The Agency agrees with the views of Wedeen:

I have reported today 19 lead workers who have lost 30 to 50 percent of their kidney function. Since they showed no symptoms and had no routine laboratory evidence of kidney disease, it may be asked why this kidney function loss should be viewed as material damage. Lead nephropathy is important because the worker has lost the functional reserve, the safety, provided by two normal kidneys. If one kidney becomes damaged, the normal person has another to rely upon. The lead worker with 50 percent loss of kidney function has no such security. Future loss of kidney function will normally occur with increasing age, and may be accelerated by hypertension or infection. The usual life processes will bring the lead worker to the point of uremia, while the normal individual still has considerable renal functional reserve. Loss of a kidney is therefore more serious than loss of an arm, for example. Loss of an arm leads to obvious limitations in activity. Loss of a kidney or an equivalent loss of kidney function means the lead worker's ability to survive the biologic events of life is severely reduced. By the time lead nephropathy can be detected by usual clinical procedures, enormous and irreparable damage has been sustained. The lead standard must be directed towards limiting exposure so that occupational lead nephropathy does not occur (Tr. 1747-1750).

And OSHA agrees with Dr. Richard Wedeen, that "40 ug/100 ml is the upper acceptable limit" (TR. 1771). That is, while PbB levels are an inadequate measure of occupational exposure (though most agree the best available single measurement) they nonetheless provide a basis for determining body burden when measured over an extended period of time. OSHA believes that maintenance of PbB levels at or below 40 ug/100 ml will reduce the overall dose to the worker, decrease the body burden of lead and prevent sufficient buildup of lead in the kidney to effect renal damage.

4. "Reproductive effects." Exposure to lead has profoundly adverse effects on the course of reproduction in both males and females. In male workers exposed to lead there is evidence of decreased sexual drive, impotence, decreased ability to produce healthy sperm, and sterility. During the hearings there was considerable discussion of the evidence submitted by Lancranjan et al. which demonstrated that the reproductive ability of men occupationally exposed to lead is interfered with by altered sperm formation. Lancanjan et al. reported a significant increase in malformed sperm (teratospermia) among lead-poisoned workmen (blood lead mean 74.5 ug/100 ml) and workmen with moderately increased absorption (blood lead mean 52.8 ug/100 ml). Decreased number of sperm (hypospermia) and decreased motility (athenospermia) were observed not only in the proceeding groups but also in those with only slightly increased absorption (blood lead mean 41 ug/100 ml). The authors concluded that these alterations were produced by a direct toxic effect on the male gonads, and that a dose response relationship exists with respect to teratospermia. The other parameters measured, hypospermia and athenospermia, do not show as strong a relationship but are significantly altered over controls. This work is consistent with other earlier literature quoted by Lancanjan.

"Epidemiologic studies have pointed out previously both the reduction of number of offsprings in families of workers occupationally exposed to lead and increase of the miscarriage rate in women whose husbands were exposed to lead. Experimental investigations have also shown both a reduction in the number of offspring of laboratory animals and reduced birth weight and survival of progenies of animals fed with diets containing lead." (Ex. 23 (Lancanjan et al.). p. 400.)

In their paper entitled "Review paper: Susceptibility of adult females to lead; effects on reproductive function in females and males" Zielhuis and Wibowo criticized the study by Lancranjan et al., and there was considerable critical discussion of it during the hearings. OSHA has concluded that methodological problems in the study do not negate the overall validity of the study especially when viewed in the context of other research in the literature. The Lancranjan study is strongly indicative of adverse effects on male reproductive ability at low lead levels, and there is evidence indicating a dose-response relationship with respect to teratospermia in these lead exposed workers. In OSHA's view altered spermatogenesis represents impaired reproductive capacity of the male given that sterility is the likely outcome. OSHA believes that this evidence and other studies support the conclusion that lead experts markedly adverse effects on the reproductive ability of males.

Germ cells can be affected by lead which may cause genetic damage in the egg or sperm cells before conception and which can be passed on to the developing fetus. The record indicates that genetic damage from lead occurs prior to conception in either father or mother. The result of genetic damage could be failure to implant, miscarriage, stillbirth, or birth defects.

The record indicates that exposure of women to lead is associated with abnormal ovarian cycles, premature birth, menstrual disorders, sterility, spontaneous miscarriage, and still-births. Infants of mothers with lead poisoning have suffered from lowered birth weights, slower growth, and nervous system disorders, and death was more likely in the first year of life.

There is conclusive evidence in the record that lead passes through the placental barrier. Multiple studies have established that the fetus is exposed to lead because of the passage of lead through the placental membrane. This evidence was uncontroverted during the hearings. The lead levels in the mother's blood are comparable to concentrations of lead in the umbilical cord blood at birth. Transplacental passage becomes detectable at 12-14 weeks of gestation and increases from that point until birth.

Numerous parties at the hearings raised the issue of whether the fetus is the most sensitive organism requiring protection from exposure to lead. Bridboard, for example, argued that the immaturity of the blood brain barrier in the newborn raises additional concern about the presence of lead in fetal tissues.

There is little direct data on damage to the fetus from exposure to lead but there are extensive studies which demonstrate neurobehavioral effects at blood leads of about 30 ug/100 ml and above in children. OSHA believes that the fetus and newborn would be at least as susceptible to neurological damage as would older children and therefore data on children is relevant to the fetus, although acknowledging the duration of exposure may be more limited in the fetus. OSHA asserts that damage to the fetus represents impairment of the reproductive capacity of the parent and must be considered material impairment of functional capacity under the OSH Act.

The proposed lead standard raised the possibility that "the risk of the fetus from intrauterine exposure to high levels of lead in the mother's blood is maximal in the first trimester of pregnancy when the condition of pregnancy may not be known with certainty" (Ex. 2, p. 45936; Ex. 95). OSHA agrees with Dr. Vilma Hunt who testified that "the first trimester has not been shown to be the period of highest vulnerability for the fetus." (Ex. 59). OSHA has concluded that the fetus is at risk from exposure to lead throughout the gestation period, and therefore protection must be afforded throughout pregnancy.

Exposure to lead would be expected to adversely affect heme biosynthesis and the nervous system earliest and most profoundly in the fetus. Early enzyme inhibition in the heme forming system has been well documented, and the central nervous system has its most significant growth during gestation and the first 2 years following birth.

Lead is capable of damaging both the central and peripheral nervous systems of children. At high exposures to lead (80 ug/100 ml and above) the central nervous system may be severely damaged resulting in coma, cardiorespiratory arrest and death. Symptoms of acute encephalopathy similar to those in adults have been reported in young children with a markedly higher incidence of severe symptoms and deaths occurring in them than in adults. In children once acute encephalopathy occurs there is a high probability of permanent, irreversible damage to the CNS. There is data that demonstrates permanent damage to CNS has occurred in children exposed at low lead levels and in whom no overt symptoms were in evidence. Children whose blood lead levels were 50 ug/100 ml and above have demonstrated mild CNS symptoms including behavioral difficulties. Behavioral disturbances in children such as hyperactivity have been associated with blood lead levels between 25 and 55 ug/100 ml. Animal studies have confirmed these findings. Beattie demonstrated an increased probability of mental retardation in children exposed to lead via maternal ingestion of lead in water. Elevated blood lead levels were found in the retarded children compared to the control group. There appeared to be a significant relationship between blood lead concentration and mental retardation. Mean blood lead for the retarded children was 25.5 ug/100 ml. Water lead concentrations in the maternal home during pregnancy also correlated with the blood leads from the mentally retarded children.

Motor nerve conduction velocity (NCV) decrements indicating early peripheral neuropathy have been reported in children. Early studies showed NCV decrements in children whose blood lead levels were 40 ug/100 g and above.

While a critical review of the literature leads to the conclusion that blood lead levels of 50 to 60 ug/100 ml are likely sufficient to cause significant neurobehavioral impairments, there is evidence of effects such as hyperactivity as low as 25 ug/100 g. Given the available data OSHA concludes that in order to protect the fetus and newborn from the effects of lead on the nervous system, blood lead levels must be kept below 30 ug/100 g. In general, 30 ug/100 g appears to be reasonably protective insofar as it will minimize enzyme inhibition (ALAD and FEP) in the heme biosynthetic pathway and should minimize neurological damage. OSHA agrees with the Center of Disease Control (Ex. 2(31)), the National Academy of Sciences (Ex. 86M), and the EPA (FEIS (92)) that the blood lead level in children should be maintained below 30 ug/100 g with a population mean of 15 ug/100 g. Levels above 30 ug/100 g should be considered elevated.

In general OSHA believes that the evidence overwhelmingly indicates the blood lead level of workers who wish to plan pregnancies should be maintained below 30 ug/100 in order to prevent adverse effects from lead on the worker's reproductive abilities. To minimize the risk of genetic damage, menstrual disorders, interference with sexual function, lowered fertility, difficulties in conception, damage to the fetus during pregnancy, spontaneous miscarriage, stillbirth, toxic effects on the newborn, and problems with the healthy development of the newborn or developing child blood lead levels should be kept below 30 ug/100 g in both males and females exposed to lead who wish to plan pregnancies.

During the hearings there was considerable testimony on reproductive effects in relation to the PEL and equal employment opportunity considerations. No topic was covered in greater depth or from more vantage points than the subject of women in the lead industry. More than a dozen witnesses testified on this issue; many others offered their views in response to questions; over 400 pages of the transcript of these proceedings were devoted to this issue. Ms. Hricko testified that women of childbearing age had been excluded from employment because "the response of industry has been to "protect women workers from lead's reproductive hazards by refusing to hire them or by forcing them to prove that they can no longer bear children." (Ex. 60 (a)(ii)). However, there was also testimony which demonstrates that women have and do work in production areas of battery manufacturing (Tr. 1245, 4057, 4506, 4855, 5529, 5898). In its proposal OSHA raised the issue of whether "certain groups of adult workers may have greater susceptibility to lead intoxication than the general worker population. One such group is female employees of childbearing age." (Ex. 2, p. 45936). The LIA argued in its post hearing brief that OSHA is not obligated to set a health standard which would insure equal employment for all persons. That is, a standard should not be promulgated which would be based on protection of the fetus and the pregnant female since that would require a lower PEL which would have correspondingly greater costs of compliance. Industry testimony further suggests that women of childbearing potential could be "protected" by excluding them from employment in many parts of the lead industry.

Other parties to the hearings argued that given the data on male reproductive abilities and potential genetic effects in males and females, fertile men were equally at risk as women of childbearing age; therefore, the standard should be designed to protect all exposed workers, male and female.

Dr. Stellman testified as follows:

In summary, it can be stated that there is no scientific justification for placing all women of childbearing age into a category of a susceptible subgroup of the working population. There is sufficient data available to show that a significant proportion of the population is at risk from the effects of exposure to lead, and hence can also be deemed susceptible. Further, if the intent of the OSHA standard is to protect workers from reproductive effects, there is still no justification for treating women separately from men. (TR. 1161-62)

This view was supported by other witnesses (Ex. 92; Ex. 343; Ex. 59;

60A). Dr. Hunt, for example, stated:

There is no evidence to allow a conclusion that women of childbearing age themselves are more susceptible to the adverse effects of lead. The susceptible population is made up firstly of the fetus in utero, actually present in the work environment and secondly the offspring of male and female workers with blood lead levels high enough to alter their genetic integrity. (Ex. 59, p. 26)

Based on the entire record, OSHA has reached the following conclusions regarding the reproductive effects of lead exposure.

A. Lead has profoundly adverse effects on the reproductive ability of male and female workers in the lead industry.

B. Lead exerts its effects prior to conception through genetic damage (germ cell alteration), effects on menstrual, and ovarian cycles and decreased fertility in women, decreased libido and decreased fertility in men through altered spermatogenesis.

C. During pregnancy, the result of lead exposure may include spontaneous abortion, stillbirth, and damage to the fetus.

D. Following birth the child of lead exposed parents may exhibit birth defects, neurological damage and the chances of death within the first year may be increased.

E. To protect against the adverse effects of lead exposure to persons planning pregnancies (or pregnant) the blood lead level should be maintained below 30 ug/100 g. Although there is no evidence for a "no effect" level, OSHA believes the risk of reproductive effects would be minimized at this level.

In conclusion, the record in this rulemaking demonstrates conclusively that workers exposed to lead suffer material impairment of health at blood lead levels far below those previously considered hazardous. Inhibition of the heme biosynthesis pathway, early stages of peripheral and central nervous system disease, reduced renal function and adverse reproductive effects are all evidence of adverse health effects from exposure to lead in workers at blood lead levels of 40 ug/100 g and above. Based on this record OSHA has concluded that blood lead levels should be maintained at or below 40 ug/100 g and even lower for workers who wish to plan pregnancies.

5. "Air to blood relationship." The proposed lead standard reduced the permissible exposure limit from 200 ug/m(3) to an 8-hour time-weighted average concentration, based on a 40-hour workweek of 100 micrograms of lead per cubic meter of air (100 ug/m(3). The Lead Industries Association (LIA) recommended that OSHA adopt a biological enforcement limit instead of using a specific airlead number for all industries and operations. One of the key questions raised by LIA in justifying a biological standard was the purported lack of a relationship between air lead levels and blood lead measurements. The purpose of this section is to address the air lead level to blood lead level relationship.

Based upon the evidence in the record OSHA has concluded that a relationship between air lead levels and population-average blood lead levels unquestionably exists and OSHA is confident that a permissible exposure limit based upon measurement of air lead levels will accomplish the intended goal of protecting worker health.

In order to accurately predict the effects on blood lead levels over time produced by changes in air lead levels, it was necessary to construct a model that takes into account the important factors which affect blood lead levels. The adaptation of the physiological model originally developed by S.R. Bernard by the Center for Policy Alternatives (CPA) combines experimentally observed properties of mammalian lead transport and metabolism, including considerations of the dynamics of blood lead response to long term exposure, with observed physical properties of airborne particulates encountered in the workplace, in order to produce a complete and accurate picture of the response of blood lead levels to particulate lead exposure. The Bernard model is an example of one of the most common types of models used to describe the transport and metabolism of drugs or foreign substances in the body, known as a multi-compartment mammillary model. Such models postulate that the substance in question first appears in the blood, and then is transported or diffused into a number of different compartments from the blood, corresponding to the different organ systems in the body. Transfer is assumed to occur only between the blood and the organ compartments, not between organ compartments. The rate of transfer into and out of the blood stream from the various compartments depends upon a number of factors, such as whether or not that particular organ specifically takes up or metabolizes the substance in question. In general, especially in the case of substances which are not metabolized, the rate of transfer between compartments is linearly related to the concentration of the substances in the compartments. This is consistent with the basic physical principles of chemical kinetics that would govern the transfer of a substance across an inert membrane in the absence of any other driving force. The relatively few exceptions to the linear transfer principle tend to occur only in cases where an organ specifically sequesters or metabolizes the substance in question.

In designing a model and calculating the rate of transfer between compartments, the experimenter has many guidelines as to how to proceed. First, one can simply follow total body excretion to ascertain the number of compartments that are individually taking up and excreting lead after an initial dose. The more exponential terms required to fit the data, the more compartments. Second, the investigator can actually follow the rate of uptake and release of the substance from the various tissues by autopsy or biopsy, and measure the rate of release. This latter approach is impossible, of course, in the study of human subjects. After observing the rates of release of the substance in question from the whole body and/or tissues, the investigator is left with a series of exponential retention equations which relate amount of lead left in each compartment after a given time to the initial dose. Using rather complicated but well-developed mathematical techniques, this set of equations can be solved subject to the constraint that all of the ingested substance is accounted for, to yield the rate constants for transfer between compartments. The CPA study also included specific consideration of particle size and individual variability in response to air lead, which is necessary in predicting the response of large populations of workers to changes in air lead exposure. OSHA has determined that the Center for Policy Alternatives (CPA) application of the Bernard Model accurately predicts the effects on blood leads over time produced by changes in air lead levels.

OSHA considers that both the basic construction of the Bernard Model of physiological lead transport and the application of the Bernard Model for prediction of blood lead levels represents a unique accomplishment heretofore unseen in attempts to establish air level to blood level relationships. Insofar as this model takes into account particle size and job tenure it has avoided the serious weaknesses of earlier studies. The findings of those previous studies were incorporated into the development of the model. The final model represents a synthesis of the best available evidence in the record with CPA application of the Bernard Model of physiological lead transport.

Participants in the hearings argued that total reliance be placed upon air sampling or biological monitoring to the exclusion of the other. OSHA will require use of both measures to maximize protection of the lead worker population in general and the individual worker in particular. However, in the enforcement context OSHA will place primary reliance on air lead level measurements to determine compliance with the permissible exposure limit. Further discussion of the permissible exposure limits is found in that section.

In order to establish the correlation between air lead levels and the corresponding blood lead levels OSHA relied in its proposal on the work of Williams et al. (Ex. 5(32)) which was the most comprehensive reported study of its kind at that time. OSHA, in this final standard, has evaluated the findings of a series of subsequent studies which became available during the rulemaking process.

Almost all of the studies, whether based on observation of general or occupational populations, attempt to relate measurements of blood lead values to observed air lead values by means of linear regression techniques. Regression analysis is a technique used to study the change of the mean value of one variable (average blood lead) as the other variable (air lead) changes. There are a number of practical and theoretical difficulties in the design and execution of experiments of this type which should be considered before attempting to discuss and compare the results of the various studies in question. The limitations of the studies in the record include:

The contribution of lead from unmeasured long term air lead exposures to current blood lead level is not properly considered. When the simple regression equation:



       Current Blood-Lead=a(Current Air Lead)+b+Individual error

           (a=slope of the line; b=blood lead at zero air lead)

is used to model the data, the blood lead contributed by the exchange of lead in bone and tissue to blood is not taken into consideration. This has the consequence that the intercept at zero current air lead exposure ("b" in the regression equation above) is biased high and the blood lead-air lead slope ("a" in the regression equation) is biased low relative to the slope which would be found if the relationship were redefined in terms of long term average blood lead level and long term average air lead exposure. This has the practical effect of incorrectly predicting that the mean PbB level at 200 ug/m(3) will be close to that at 100 ug/m(3), which was a criticism made by LIA during the hearings. To the degree that the contribution of prior exposure to current blood lead levels differs for different workers in the sample, the "individual error" term will also be increased.

The regression equation does not explicitly incorporate terms relating to particle size. If, as suggested by some data in the record, workers at high air lead exposure levels are exposed to a larger proportion of poorly- absorbed larger particulates than workers at low air lead levels, then this will cause an additional upward bias to the "b" zero occupational exposure intercept and a downward bias to the "a" blood lead-air lead slope coefficient. This creates an impression that the rate at which blood lead changes relative to the air lead would be less than it actually would be.

Measurement errors of different kinds affect the results in different ways. Any errors in measuring blood lead level will add to the "individual error" term. However, errors in measuring air lead levels (arising either from inevitable imprecision in sampling or analysis or from unrepresentativeness of the short sample period relative to true average exposure) will usually systematically bias the "a" blood lead-air lead slope downward. This is a particularly serious source of bias in one of the major studies, the Buncher analysis (Ex. 285) of the Delco-Remy data, where single air lead measurements were paired with blood level determinations made within a month of the air sampling. All other major studies of air lead-blood lead relationships used averages of several independent air lead measurements (generally ten or more measurements) for assessments of individual worker air lead exposures.

None of the studies made measurements of work-load or total worker respiration on the job. To the degree that workers differ from each other in gross ventilation, the individual error term is larger than it might have been. To the degree that populations of workers in different plants or in different industries differ in average respiration rate, potentially controllable or avoidable discrepancies in the results of different studies may have been produced.

Viewed in this context, the fact that there are differences in the blood lead-air lead regressions derived from short term observations on different populations is hardly surprising. It is also understandable that many of the studies find unreasonably high values of the intercept at zero exposure ("b"). From studies of general populations with no occupational lead exposure, it is clear that the true "b" intercept is certainly under 25 ug/100g, and is very probably under 20 ug/100g for most areas.

The following table summarizes the results of the regression analyses developed from the studies in the hearing record. This table also compares the studies to the model and demonstrates that even given the limitations of the studies the results are similar.


          TABLE 1. -- SUGGESTED AIR LEAD/BLOOD LEAD RELATIONSHIPS

                           LINEAR RELATIONSHIPS

                       Blood Lead = a(Air Lead) + b
_________________________________________________________________________

Source of Relationship                b      a         Non-Linear
_________________________________________________________________________

King: Smelting (3).............       52     0.053
     Battery(1)................       46      .032
     Pigments(2a)..............       30       .07
Pigments.......................                             (1)
(Quadratic fit)................
Globe-Union....................     39.7     .1229
ASARCO (EL Paso)...............       82      .185
Williams.......................     30.1      .201
Delco-Remy (Buncher)...........    37.45     .0628
     Azar/Hammond..............                             (2)
CPA: Bernard model and
     assumption C..............
       Job Tenure (years)
0.95...........................    25.80     .1521
3.4............................    28.30     .2062
9.0............................    29.80     .2404
16.0...........................    30.64     .2604
28.5...........................    31.46     .2778
________________________________________________________________________
  Footnote(1) Blood Lead = 26 + .12  (Air lead) + .000098  (Air Lead)(2)
  Footnote(2) Log(Blood Lead) = 1.3771 + .153 log 40(Air) + 128 divided by
168.

The available studies also have some individual limitations which should be borne in mind when considering the results:

The King studies (Ex. 234(22)) included many workers exposed at very high (300-900 ug/m(3)) air lead exposure levels. There is reason for concern that (1) because of particle size and absorption effects, the blood lead-air slope at very high air lead levels may not accurately reflect the slope in the air lead exposure region of interest for standard-setting (25-200 ug/m(3)), and that (2) there is a risk that selection effects may have biased the observed air lead slope low; some workers who show high blood lead levels in response to a given air lead level may be absent from the high air lead exposure groups because of medical transfer to lower or no exposure jobs.

The Globe Union study (Ex. 150A) is based on a relatively small sample, although many of the sample points are of better quality than the points of other studies because they are based on averages of many air lead and blood lead determinations over a relatively long time (6 months or more).

The ASARCO El Paso (Ex. 142 D) and Williams (Ex. 2(32)) studies each measured air lead and blood lead levels over a quite brief period (2 weeks). Additionally, the use of a control group of plastics workers at low air lead exposure levels in the Williams study has been criticized on the ground that the particulate air lead of the plastics workers' exposures may have been qualitatively (particle size, solubility) different from the exposures of the battery workers at higher air lead exposure levels.

The Azar/Hammond relationship (Ex. 54) is an extrapolation of data from non-occupational exposures far below the exposure range of occupational situations. Use of a logarithmic model for such extrapolation is without theoretical justification.

As summarizations of available data on different populations, the existing studies are reasonably valid. It is one thing to say, however, that a linear relationship was observed between the blood lead levels and the air lead exposure at a given level of statistical significance, for a given sample or workers, and another thing entirely to use the observed relationship to predict the effect of lowering air lead exposure on even that same sample of workers, let alone to generalize to other samples. Generally, data obtained at a given point in time, should be used conservatively when attempting to predict effects over time. Rarely will all other factors be held constant.

Recognizing these limitations by no means should be taken to imply that the data are useless or that no reliable relationship exists between long term air lead exposures and blood lead levels. To the extent that the likely systematic errors in the short term studies are understood (e.g., overestimation of the blood lead-air lead slope coefficient and overprediction of the intercept at zero occupational exposure), the observed regressions can be used to bound estimates of the true long-term relationships of blood lead to occupational air lead exposure. To the extent that the sources of uncontrolled variation within and between studies are understood, estimates of the likely effects of such factors can be explicitly incorporated into a more comprehensive description of the general system.

Because of the deficiencies in observational studies of air lead-blood lead relationship, it is useful to supplement the empirical air lead-blood lead correlations with relationships derived from physiological models of lead transport in the body. As previously stated the weight of the evidence demonstrates that the model developed by the Center of Policy Alternatives (CPA) is an accurate tool for assessing the blood lead level response to alternative air lead exposures.

In order to predict the numbers of workers who will be above a given blood level at any one time, it is necessary to have an estimate of the spread of individual workers' blood lead levels about a population mean. Observed variability in a worker population will have three basic components:

(1) Individual differences in the long term (years) average blood level response to a given air lead level;

(2) Individual differences resulting from true short term (days or weeks) fluctuations in blood lead level; and

(3) Apparent short term variability from measurement error. Based on an analysis of data from the Delco-Remy battery plant, it is estimated that true long term blood lead variability corresponds to a standard deviation of approximately 5.5 ug/100g. This is likely to be an underestimate of true long term differences in blood lead resulting from a constant air lead exposure because a single plant over a limited time is unlikely to include as large a diversity in the many factors producing long term variability as would prevail in a random sample of all lead-using industries. The value of 9.5 ug/100g, used in the previous CPA work as an upper bound on true long term variability, appears to be the best mid-range estimate of total (short and long term) true variability. A high range estimate for total variability (including measurement error) suggested in the record is approximately 15 ug/100g. OSHA has used a standard deviation 9.5 ug/100g in calculating the distribution of blood lead levels at particular air lead levels. This distribution has then been utilized to calculate the incremental benefits of the permissible exposure limit over the other alternatives of 40 ug/m(3), 100 ug/m(3) and 200 ug/m(3). The results are found in the benefits subsection of the PEL section.

B. PERMISSIBLE EXPOSURE LIMIT

1. "General considerations." The final standard establishes a permissible exposure limit (PEL) of 50 ug/m(3) averaged over an eight hour period. The decision to establish this PEL was based on consideration of the health effects associated with exposure to lead, feasibility issues, and the correlation of airborne concentrations of lead with blood lead levels that are in turn associated with adverse effects and symptoms of lead exposure.

At the time the proposal was issued, OSHA stated that "in order to provide the appropriate margin of safety, as well as to provide significant protection against the effects, clinical or subclinical, and the mild symptoms which may occur at blood lead levels below 80 ug/100 g it is necessary to set an airborne level which will limit blood lead (PbB) levels to 60 ug/100 g. A maximum blood lead level of 60 ug/100 g corresponds to a mean blood lead level of about 40 ug/100 g" (Ex. 2, p, 45938). Based upon the extensive evidence of adverse health effects associated with exposure to lead, OSHA has determined that in order to provide necessary protection against the effects of lead exposure, the blood lead level of lead workers must be kept below 40 ug/100 g.

In establishing 40 ug/100 g as the maximum blood lead level which the protection of employees and prudence permits, OSHA is mindful of the requirement of the Act the "no employee will suffer material impairment of health or functional capacity . . . for the period of his working life." OSHA has concluded that maintenance of blood lead levels below 40 ug/100 g by engineering and work practice controls of airborne lead will provide protection of workers throughout their working lifetimes. There is a substantial amount of evidence which indicates that the blood lead level of workers, both men and women, who wish to plan pregnancies should be maintained at less than 30 ug/100 g during this period, and this knowledge forms the basis for the action level of 30 ug/m(3) established in this final standard which the agency believes will maintain the majority of blood lead levels below 30 ug/100 g.

OSHA recognizes that a PEL of 50 ug/m(3) will not achieve the goal of maintaining the blood lead levels in all occupationally exposed workers below 40 ug/100 g. Based on the calculations using the CPA adaptation of the Bernard model, OSHA predicts 0.5 percent of worker blood leads will exceed 60 ug/100 g; 5.5 percent of the workers will have a PbB between 50-60 ug/100 g; 23.3 percent will be between 40-50 ug/100 g; and overall, 29.3 percent of exposed lead workers will have PbB above 40 ug/100 g at any one time when uniform compliance with 50 ug/m(3) PEL is achieved. However, this represents a substantial improvement over current industry conditions. The current blood lead level distribution assuming compliance with 200 ug/m(3) is approximately (1) greater than 60 ug/100 g, 22.4 percent; (2) 50-60 ug/100 g. 32.6 percent; (3) 40-50 ug/100 g, 28.7 percent; (4) The total above 40 ug/100 g. 83.8 percent.

In establishing 40 ug/100 g as a maximum desirable blood lead level, the Agency is conscious of the fact that the OSHA Act mandates that a standard be set which meets the test of feasibility. OSHA has determined that 50 ug/m(3) represents the lowest level for which there is evidence of feasibility for primary and secondary smelting. SLI battery manufacturing, pigment manufacturing, and brass/bronze foundries. The 50 ug/m(3) exposure limit is the level which properly balances the questions of feasibility and health effects of lead exposure and most adequately assures, to the extent feasible, the protection for workers exposed to lead. Compliance with this level will provide a dramatic reduction in the number of workers whose blood lead levels are currently greater than 40 ug/100 g, and will virtually eliminate all blood lead levels above 60 ug/100 g.

This level of 50 ug/m(3) is achievable almost entirely through engineering and work practice controls, the preferable control strategy. The exposure limit is based upon what can be achieved by the affected industries taken as a whole, using presently available technology or, in some industries, technology looming on the horizon. The industries which will face the greatest difficulties in the implementation of engineering controls will be primary and secondary smelters, pigment manufacturing, brass/bronze foundries and SLI battery manufacturers. For this reason, the requirement for engineering and work practice controls will be phased-in with extended periods of time allotted for compliance in these industries. OSHA has determined that the standard is feasible, and that the PEL of 50 ug/m(3) represents the best intersection between maximization of health benefits and feasibility.

2. "Health effects." In the proposal, OSHA questioned whether both clinical and subclinical effects of exposure should be considered in establishing a standard for lead. OSHA believes the original terms, clinical and subclinical, represent vast over-simplifications of a disease process and, therefore, have avoided their use in this final standard. The subclinical effects described in the health effects section are, in reality, the early to middle stages in a continuum of disease development process. It is axiomatic that the chronic, irreversible stage is preceded initially by an early, relatively mild, and apparently reversible stage of disease. This earliest stage is characterized by varying subjective and/or objective symptoms which may not at first alarm the victim, or present a physician with a clear-cut diagnosis. Nevertheless, this early developmental stage of disease is a pathological state, and OSHA finds persuasive the arguments for adopting a lead regulation which protects workers from this early consequence of lead exposure. OSHA believes these early stages of the disease process characterized by central nervous system symptoms, behavioral changes, psychological impairment, peripheral nerve damage, anemia, reduced kidney function and adverse reproductive effects represent material impairment of the worker and should be prevented in order to eliminate further development of disabling disease and death.

OSHA must promulgate a standard which prevents occupational disease resulting from both acute and prolonged or chronic exposure to lead; it must likewise guard against the onset, progression or severity of chronic degenerative diseases of aging workers. The degree of protection to be provided must extend over the full span of a working life and must cover the more susceptible, as well as the more robust members of the exposed group. Since the objective is to limit the latent effects of exposure, as well as immediate illness, the mere absence of illness, or lack of severe clinical signs will not constitute adequate health protection. The PEL must be chosen such that it protects the worker not only from the most overt symptoms of illness, but also from the earliest indications of the onset of disease. The usual medical signs for disturbance, therefore, are wholly inadequate to provide employee protection. These considerations formed the basis of OSHA's interpretation of the health effects data in the record for purposes of establishing a PEL.

a. "Inhibition of heme synthesis." In establishing the PEL, OSHA evaluated the health effects of lead on heme synthesis. Scientific evidence has established that very low levels of lead inhibits at least two enzymes (ALA-D and ferrochelatase) in the heme synthesis pathway. ALA-D inhibition is observed at PbB levels below 20 ug/100 g. At 40 ug/100 g significant excretion of the substrate of one enzyme, ALA-D occurs at this PbB level. The build-up of protoporphyrin levels indicates that inhibition of the enzyme, ferrochelatase, also occurs at low PbB levels. Some have argued that these effects are the manifestation of the human body's adjustment to lead. OSHA believes that it is inappropriate and simplistic to describe these changes as internal adjustments. These measurable effects are considered by the agency to indicate the occurrence of disruptions of a fundamental and vital subcellular process, heme synthesis, such processes are not only essential to the production of hemogloblin, they are also vital to the mitochondrial function of all cells.

OSHA believes the evidence indicates a progression of lead's effects starting with the inhibition of specific enzymes, continuing to the measurable disruption of subcellular processes, such as the measurable build-up of heme synthesis products, and eventually developing into the overt symptoms of lead poisoning. Biological variability between individuals will necessarily cause differences in the PbB level at which a particular person will experience each stage in this disease continuum; therefore, at each higher PbB level a greater proportion of the population will manifest each given effect. Given this understanding of the progressive stages of lead's effect, OSHA has concluded that enzyme inhibition indicative of the disruption of heme synthesis is an early stage of a disease process.

Anemia is one of the established symptoms of lead poisoning. That lead-induced anemia occurs above PbB levels of 80 ug/100 g is well established; however, the occurrence of this symptom at PbB levels below 80 has been debated. In evaluating the disease mechanisms of anemia, it was found that lead is an insidious poison which attacks not one, but many, of the subcellular physiological processes. The effects of lead on heme synthesis are considered to play a part in the development of anemia. Studies have associated PbB levels as low as 50 ug/100 g with lowered Hb levels. In particular, Tola's study, which showed a lowering of hemoglobin (Hb) over the length of lead exposure to 50 ug/100 g, and the work of the Mt. Sinai group in secondary smelters which demonstrated reduced Hb in 39 percent of the workers studied whose PbB levels ranged from 40 to 80 ug/100 ml, is considered by OSHA as strong evidence that lead does effect reduced Hb levels at this low PbB range. This implies that there is a lifetime alteration in the oxygen carrying capacity of the blood, in the blood viscosity and potentially in the cardiac work load.

In evaluating the effects of lead on heme synthesis, Piomelli suggested that effects on the blood forming system, such as anemia, are not the most significant clinical effects of heme synthesis disruption nor the earliest. He stated that "a much more important fact is that the alteration of the mechanism of heme synthesis reflects the general toxicity of lead in the entire body." (TR 458) Evidence indicates that there is disruption of heme synthesis in other tissues of the body following exposure to lead, and that this disruption results in alteration of the process of respiration. While this evidence relates lead's effects on heme synthesis to symptoms throughout the body is far from complete, it is, however, extensive enough to warrant very serious consideration with respect to the establishment of the standard. OSHA believes this evidence demonstrates that one stage of early lead disease is the disruption of heme synthesis and that the measurable effect of this disruption on the hematopoietic system parallels that which is known to occur in all body tissues at comparably low PbB levels, (below 40 ug/100 g). The disruption of heme synthesis is clearly not the only mechanism by which lead exerts its toxicological effect, but is one mechanism of which we have substantial understanding and can measure.

In reference to the blood forming system, OSHA believes that the effects of lead are a complex progression which begins with discrete biochemical changes and proceeds to overt clinical symptoms. At increasingly higher PbB levels, a significant proportion of the population will suffer more extreme effects. At a PbB level of 40 ug/100 g, a sizable proportion of the population would show measurable effects of the disruption of heme synthesis in the hematopoietic system. A comparable degree of disruption of heme synthesis in the mitochondria would occur. OSHA believes the occurrence of such effects is an unacceptable health impairment.

Piomelli gave an excellent summary of the importance of lead's effects on heme synthesis stating:

It is my understanding that regulations have the purpose of preventing "material impairment of health". Alterations in heme synthesis do not produce subjective evidence of impairment of health, unless they reach the extreme depression in severe lead intoxication, when marked anemia occurs and the individual feels weak. However, it is not any longer possible to restrict the concept of health to the individual's subjective lack of feeling adverse effects. This is because we know that individuals may get adjusted to suboptimal health, if changes occur slowly enough and also because we now have the ability to detect functional impairments by appropriate tests, much before the individual can perceive any adverse effect. In fact, it is the responsibility of preventive medicine to detect those alterations which may proceed frank symptomatology, and to prevent its occurrence. The alterations in heme synthesis caused by lead fulfill, in my opinion, the criteria for material adverse effects on health and can be used to forecast further damage. The depression of heme synthesis in all cells of the body is an effect of far reaching proportion and it is the key to the multiple clinical effects of lead toxicity, which becomes obvious as the exposure continues (Ex. 57, p. 21).

This does not in any way suggest that the lead effect on heme is the only mechanism of lead disease, but it does suggest that this effect is at least one of the important mechanisms in lead disease. An understanding of the spectrum of effects from subcellular to clinical symptoms is relevant not only to the occurrence of anemia but will also be the expected pattern in lead-induced neurological and renal disease.

OSHA believes that there is evidence demonstrating the impairment of heme synthesis and mitochondrial disruption in tissues throughout the body, and that these effects are the early stages of lead disease in these various tissues. The disruption of heme synthesis measured at low PbB levels is not only a measure of an early hematopoietic effect, it is also a measure which indicates early disease in other tissue. The Agency believes that such a pervasive physiological disruption must be considered as a material impairment of health and must be prevented. PbB levels greater than 40 ug/100 g should, therefore, be prevented to the extent feasible.

b. "Neurological system." There is extensive evidence accumulated in both adults and children which indicates that the toxicity of lead is manifested in both the central and peripheral nervous systems. The neurologic manifestations of lead intoxication are variable, ranging from acute, chronic, or low level to massive. The location and degree of neurological damage depends on the dose and duration of exposure.

The record in this rulemaking clearly demonstrates that damage occurs in both the central and peripheral nervous systems at blood lead levels lower than previously recognized. Based on this record, OSHA has concluded that the earliest stages of central nervous system disease are recognizable as subjective CNS symptoms and behavioral disorders. These disorders have been documented in numerous scientifically sound investigations. Current information does not provide an indication of a no-effect level. In adults, there is evidence of a dose-response relationship, but the no-effect level remains to be determined. Given the severity and potential nonreversibility of central nervous system disease. OSHA must pursue a conservative course of action. A blood lead of 40 ug/100 g must be considered to be a threshold level for behavioral changes in adults, and to protect against long term behavioral effects, blood levels should never exceed 60 ug/100 g.

Some of the best and most extensive evidence in the rulemaking record are the data presented which confirm the existence of the early stages of peripheral neuropathy in workers exposed to lead levels below 70 ug/100 g. The evidence demonstrates that there is a statistically significant loss of motor nerve conduction velocity (MNCV) in lead-exposed workers. A dose-response relationship for the slowing of MNCV has been determined, and it is apparent that this slowing occurs in workers whose PbB levels are 50 ug/100 g and above. Whether there are effects as low as 40 ug/100 g is as yet undetermined, although Repke does indicate a slowing of MNCV in the forties. Recently published research indicates edema appears to develop at the same time of onset of degeneration of myelin sheaths of nerve fibers which show reduced MNCV. This pathophysiologic state will grow progressively worse with continued exposure even at PbB levels in the fifties. OSHA believes a clear deficit in the conduction velocity of more than one nerve is an early stage in the development of clinically manifest peripheral nerve damage and disease (neuropathy).

In order to prevent peripheral neuropathy as evidenced by a slowing in NCV's, it is necessary to maintain PbB's below 50 ug/100 g, although if there is to be any margin of safety, a value less than this should be established. This is consistent with OSHA's overall goal of maintaining blood leads below 40 ug/100 g.

Recovery from the effects of chronic lead poisoning may be feasible in some cases if the worker is removed from the source of exposure and therapy is initiated immediately. There are instances, however, when complete recovery is impossible and the pathology is fixed. Even if the worker is removed from the source and therapy initiated, the worker may still experience impairment (Ex. 95 Ref. Cantarow p. 135). In a recent paper describing his results, Dr. R. Baloh, a neurologist at UCLA questioned the reversibility of nervous system damage:

Although there are isolated reports of significant improvement in lead induced motor neuron diseases and peripheral neuropathy after treatment with chelation therapy, most studies have not been encouraging, and in the case of motor neuron disease, death has occurred despite adequate chelation therapy.

All of this data reinforces a disturbing clinical impression that nervous system damage from increased lead absorption is only partially reversible, if at all, with chelation therapy and/or removal from further exposure. This is not particularly surprising however, since experience with other heavy metal intoxication has been similar. Nervous system damage from arsenic and mercury responds minimally to chelation therapy. Apparently, irreversible changes occur once the heavy metal is bound by nervous tissue. Although further study is clearly needed, the major point I would like to make this morning is that there is strong evidence to suggest the only reliable way to treat nervous system damage from increased lead absorption is to prevent its occurrence in the first place. (Ex. 27(7) p. 55.)

OSHA agrees with these concerns regarding irreversibility of neurological disease expressed by Dr. Baloh and therefore must establish a standard which will prevent the development of nervous system pathology at its earliest stages.

c. "Renal system." During the hearings, one of the most important contributions to the understanding of the adverse health effects associated with exposure to inorganic lead was the elucidation of evidence on kidney disease. In particular, the research of Wedeen and his coworkers, the health hazard evaluation by NIOSH at Eagle Picher Industries, Inc., and the work of the Mt. Sinai group demonstrated that lead exposure is a key etiologic agent in the development of kidney disease among workers occupationally exposed to lead. Unlike the hematopoletic system where changes in heme formation can be detected at early stages, renal disease may only be detected through routine screening after serious damage has occurred. Elevated BUN and S-creatinine are measurable only after two-thirds of kidney function is lost, or upon manifestation of symptoms of renal failure. OSHA agrees with the conclusions of Wedeen: "By the time lead nephropathy can be detected by usual clinical procedures, enormous and irreparable damage has been sustained. The lead standard must be directed towards limiting exposure so that occupational lead nephropathy does not occur," (Tr. 1750) since in this situation "progression to death or dialysis is likely." (Tr. 1732). The record indicates that blood lead is an inadequate indicator of kidney disease development, since rather than being a complete measure of body burden, it is merely a measure of absorption when sampled close to the time of exposure.

Given these conclusions, OSHA must approach the prevention of kidney disease by recognizing the limited usefulness of certain biological parameters. Therefore, OSHA believes any standard established for lead must provide some margin of safety and agrees with Dr. Wedeen that:

It is therefore the subclinical renal effects, and by subclinical, I mean effects that are not readily detected by the patient or the physician, it is therefore the subclinical effects of lead which should be detected and prevented, since this represents a material loss of functional capacity which has serious adverse health implications. (Tr. 1732) 40 ug/100 ml is the upper acceptable limit to prevent development of a hazardous body burdens lead. (Tr. 1771)

d. "Reproductive system." The record clearly demonstrates that lead has profoundly adverse effects on the course of reproduction. Prior to conception exposure to lead is responsible for menstrual and ovarian cycle abnormalities in women, decreased libido, impotence and altered sperm formation in men, and lowered fertility and genetic damage in both males and females. Genetic damage may result in spontaneous miscarriage, stillbirth, or in a disease or birth defects in a live born child. There is data which documents that miscarriage and stillbirth may be caused by maternal lead exposure during pregnancy. In fact, lead has been used as a abortifacient. In women exposed to lead. Fhim has reported that the mothers of premature babies had significantly higher mean blood leads than did mothers with normal pregnancies.

There is conclusive evidence that lead crosses the placenta of pregnant women and enters the fetal tissues; lead levels in the mother's blood are comparable to concentrations in the umbilical cord blood at birth. A survey of fetal tissue demonstrated that the transplacental passage of lead becomes detectable at 12 to 14 weeks of gestation, and increases from that point to birth. Therefore, early in pregnancy the fetus may be adversely affected by maternal lead exposure. Some investigators have suggested that the fetus is most vulnerable to lead during the first trimester. OSHA disagrees with this assertion, but rather believes the fetus is highly vulnerable whatever the stage of development. The fetus is particularly susceptible to neurological damage. In addition, there may also be heme synthesis impairment and renal damage in the fetus. In the newborn child, exposure to lead may continue through the secretion of lead in the mother's milk.

There is little direct data on damage to the fetus from exposure to lead but there are extensive studies which demonstrate neurobehavioral effects in children. OSHA believes that the fetus would be at least as susceptible to heme inhibition and neurological damage as would older children and therefore data on children is relevant to the fetus.

Behavioral disturbances, such as hyperactivity, have been associated with blood lead levels in children as low as 25 ug/100 ml. In general, mild CNS symptoms, behavioral problems, and other neurological signs and symptoms occur around 50 ug/100 ml, but there is evidence of adverse effects at lower PbB levels.

An analysis of the data suggest that in order to protect against lead's adverse effects on the course of reproduction, blood lead levels should be maintained at or below 30 ug/100 ml. The Center for Disease Control, the Toxicology Committee of the National Academy of Sciences and the Environmental Protection Agency recommended that blood lead levels of children be kept below 30 ug/100 ml. Certainly the fetus and newborn should be similarly protected. OSHA recognizes that the PEL of 50 ug/m(3) acting alone will not maintain blood lead levels of persons planning pregnancies or pregnant women below 30 ug/100 ml. When compliance is achieved, the mean blood lead level for a population of lead workers uniformly exposed to the 50 ug/m(3) PEL will be approximately 35 ug/100 ml. OSHA believes that damage to the fetus represents impairment of the reproductive capacity of the lead exposed parent. While OSHA believes that a standard should be set which protects all persons affected -- male and female workers, and the fetus -- the agency is limited by the requirement that a standard be feasible. However, the standard minimizes adverse reproductive effects from lead by a variety of means including (1) establishing a 30 ug/m(3) action level which will initiate biological and air monitoring, (2) utilizing the provisions of the medical surveillance section, including fertility testing, physician reviews, and medical removal protection to identify and perhaps remove workers who may wish to plan pregnancies or who are pregnant, and (3) insuring through the education and training provisions of the standard that workers are fully informed of the potential hazards from exposure to lead on their reproductive ability, during pregnancy and following birth. Compliance with these provisions of the standard should effectively minimize any risk to the fetus and newborn child, and thereby protect the reproductive systems of both parents.

The record in this rulemaking is clear that male workers may be adversely effected by lead as well as women. Male workers may be rendered infertile or impotent, and both men and women are subject to genetic damage which may affect both the course and outcome of pregnancy. Given the data in this record, OSHA believes there is no basis whatsoever for the claim that women of childbearing age should be excluded from the workplace in order to protect the fetus or the course of pregnancy. Effective compliance with all aspects of this standard will minimize risk to all persons and should therefore insure equal employment for both men and women. There is no evidentiary basis, nor is there anything in this final standard, which would form the basis for not hiring workers of either sex in the lead industry.

During the hearings, industry representatives argued that lead exposed workers will not suffer material impairment of health if blood lead levels are below 80 ug/100 g. OSHA finds this argument to be unsubstantiated by scientific or medical evidence, and has concluded that it represents an incorrect assertion. It is not based on the sound evidence in the record which demonstrates adverse health effects as low as 40 ug/100 g. The record indicates that adverse signs and symptoms have been observed in workers who were exposed to lead for less than a year.

During the public hearings the vast majority of the physicians who testified supported the view that blood lead levels should be maintained at or below 40 ug/100 g in order to protect against the onset of the early manifestations of disease previously described as subclinical effects. The following physicians supported a PbB level of 40 ug/100 g: Dr. Lillis (Tr. 2700-01), Dr. Needleman (Tr. 1085-86; 1106-07); Dr. Epstein (Tr. 1051-52, 1058-65, 1067-68, 1072, 1073-74, 1104-05); Dr. Lancrajan (Tr. 1771), Dr. Wolfe (Tr. 4140), Dr. Teitlebaum (Tr. 374-78), Dr. Bridbord (Tr. 1976-02), Dr. Fishbein (Tr. 2660-61, 2669) and Dr. Piomelli (Tr. 467).

In addition OSHA has carefully scrutinized the extensive evidence compiled by the Environmental Protection Agency (EPA) which led that Agency to establish a national ambient air quality standard of 1.5 ug/m(3) designed to address the problem of lead in the urban environment. The EPA standard was based on the following considerations:

In establishing the final standard, "EPA determined that of the general population, young children (age 1-5 years) are the most sensitive to lead exposure. In 1970, there were 20 million children in the U.S. under 5 years old, of whom 12 million lived in urban areas and 5 million lived in center cities where lead exposure is the highest. The standard is based on preventing children in the U.S. from exceeding a blood level of 30 micrograms lead per deciliter of blood. Blood lead levels above 30 micrograms are associated with an impairment in cell function which EPA regards as adverse to the health of chronically exposed children. There are a number of other adverse health effects associated with blood lead levels above 30 micrograms in children as well as in the general population, including the possibility that nervous system damage may occur in children even without overt symptoms of lead poisoning." (EPA Press statement, September 29, 1978.)

These conclusions are consistent with the testimony in this record including the policy statements of the Center for Disease Control (Ex. 2 (15)) and the National Academy of Sciences. These conclusions on exposure limits in the general population and children in particular are relevant to OSHA's final standard for a working population. The testimony of Dr. H. Needleman of Harvard University is relevant here.

I am one of those who believe that a substantial body of evidence is accumulating that the threshold for significant health effect depends on the avidity, sensitivity and sophistication with which we pursue it and that the lowering of acceptable body burdens in children and adults is scientifically and economically sound.

With the passage of time, the defined acceptable blood level for a child under six has moved from 60 -- when I began my training in pediatrics not too long ago -- to 50 to 40 micrograms per deciliter. The CDC now begins to talk about 20 as the threshold for undue lead exposure. And Professor Zielhuis at the Amsterdam meeting in 1972 recommended an individual limit of 35 micrograms per deciliter and a group average of 20 micrograms per deciliter for children.

There are important differences during the time that the blood brain barrier is being laid down, in that certain enzymes are being induced, but I think that the point that I was trying to generate in that argument, was that in my pediatric experience, when I started training in pediatrics, we said that children with blood leads over 80 were at high risk for the lead poisoning, and now we have been talking about children of 30, 45 or 40, and I think that same argument, deriving out of sharp and clinical and experimental evidence, would apply to the worker that is, that if you look more carefully for evidence of impairment, you are going to find it.

The fact that an adult worker will spill aminolevulinic acid in his urine, at a blood lead of 40, to me says, that this is a clinical effect of significance. (Tr. 1078, 1106-07.)

The Agency agrees with the conclusions of Dr. Needleman and emphasizes that overt symptoms of lead toxicity occur below 80 ug/100 g and in fact below 60 ug/100 g. OSHA is convinced by the record that large numbers of workers whose blood lead levels are above 40 ug/100 g and whose health will in all probability grow progressively worse, must be identified and protected.

e. "Air to blood relationships." In order to establish a permissible exposure limit, OSHA was first required to determine the blood levels associated with adverse effects and symptoms of lead exposure, and to correlate these blood lead levels with airborne concentrations of lead. During the hearings, industry representatives steadfastly maintained that blood lead levels cannot be correlated with, nor predicted from air-lead concentrations. Based on the record evidence, OSHA has concluded to the contrary. While many studies in the record have limitations, these limitations by no means imply that the data are useless or that no reliable relationship exists between long term air lead exposures and blood lead levels. Given the extent to which the likely systematic errors in the short term studies in the record are understood, the observed equations can be used to bound estimates of the true long term relationships of blood lead to occupational air lead exposure. To the extent that the sources of uncontrolled variation within and between studies are understood, estimates of the likely effects of such factors could be explicitly incorporated into a more comprehensive description of the general system.

In order to accurately predict the effect on blood lead levels which would be caused by long term exposure to various levels of air lead, it was necessary to construct a model that takes into account the important factors which affect blood lead levels. The physiological model originally developed by S.R. Bernard and adapted by the Center for Policy Alternatives (CPA) combines experimentally observed properties of mammalian lead transport and metabolism, including consideration of the dynamics of blood lead response to long term exposure. The model also accounts for the observed physical properties of airborne particulates encountered in the workplace, in order to produce a complete and accurate picture of the response of blood lead levels to particulate lead exposure. Furthermore, the CPA study includes a specific consideration of individual variability in response to air lead, which is necessary in predicting the responses of large populations of workers to changes in air lead exposure. OSHA believes this model represents the best approximation of the true air lead to blood lead relationship to date. It is superior to the short term studies in the record, insofar as it incorporates the best aspects of the studies in the model and also addresses the particular weaknesses of these studies, such as job tenure and particle size. OSHA has utilized the model in calculating the predicted blood lead distributions at various air lead levels and has determined the incremental benefits of the PEL to be discussed in the next section.

3. "Benefits of the PEL." The dramatic reduction in the number of workers with blood lead levels over 40, 50 and 60 ug/100 g. is a measure of the incremental benefit derived from a PEL of 50 ug/m(3). Ideally, it is desirable to express the benefits of a standard in terms of decreases in the incidence and severity of the various adverse health effects of lead exposure (e.g., neurological damage, kidney damage, etc.). However, the available data does not allow a meaningful quantitative estimation of the degree of prevention of damage which is likely to be achieved by lowering worker exposures and blood leads to specific levels. The record evidence allows estimates to be made of the blood lead levels which are likely to result from compliance with alternative air standards. In the absence of better epidemiologically determined morbidity and mortality data, the best judgment of the relative health benefits achievable under the different PEL's which have been considered is based on the expected reduction in the number of workers with dangerously high blood lead levels.

The results are expressed in terms of the number of workers expected to fall into a particular blood lead range at any one time after the establishment of long-term equilibrium, and without consideration of medical removal provisions. OSHA believes that this model will provide the best comparison of different assumed compliance levels. However, there are a number of inherent limitations in this approach which need to be clearly appreciated.

First, it should be understood that a change in air lead exposure causes a shift in the entire distribution of blood lead levels in the population:

                     Figure 1

(For Figure 1, Click Here)

Although the incremental benefits of standard No. 1 over standard No. 2 may be expressed in terms of the decrease in the number of workers (area under the curve) falling in each blood lead level range, the "benefits" of the standard are not really limited to workers who move across the lines drawn at 40, 50, and 60 ug/100 g. Under the lower exposure standard, all of the workers are expected, to some degree, to have lower blood lead levels, and therefore possibly some lower level of health risk. It should be noted that the comparison of differences in mean blood lead levels will markedly under-estimate the benefits to a population of workers.

Second, it should be stressed that the measurement of benefits chosen represents a continuous "flow," not a "stock." As time passes and workers move into and out of employment in lead-related industries, the differences between compliance with various PEL's continuously generate differences in the population of newly exposed workers. If two standards differ by 1,000 in the number of workers expected to be over 60 ug/100 g at any one time, over a period of 10 years, the difference is clearly 10,000 person-years at the higher blood lead level. This figure depends on the labor turn-over in the industries concerned, the frequency with which workers change jobs (and hence exposures) within the industry, as well as other factors.

D.B. Associates has presented rough estimates of lead exposure in many industries. OSHA bases its assessments of the incremental benefits of the air lead standard on this data, as it is the most comprehensive compilation of exposure estimates. OSHA estimates based on DBA figures and other record evidence that overall, approximately 41,622 workers are currently exposed to time-weighted-average air lead levels of over 100 ug/m(3), and an additional 55,885 workers are exposed to air lead levels between 50 and 100 ug/m(3).

The following results are obtained by multiplying the appropriate exposure estimates by the estimates of the percentages of population expected to have blood levels in each range at any one time, following the establishment of long-term equilibrium. (See Figure 2 and Table 2.)

                       Figure 2

(For Figure 2, Click Here) Table 2 BEST POINT ESTIMATES OF ULTIMATE EQUILIBRIUM BENEFITS OF REDUCING AIR LEAD EXPOSURES Blood Level Standard Deviation = 9.5 ug/100g Long Term Total Less than Total Average Number or = to 50-60 40-50 less than Air Lead of 60 ug/100g ug/100g or = to Exposure Workers ug/100g 40 ug/100g a. Current Compliance Level > 100 ug/m(3) 41,622 27,652 8,508 4,166 40,326 50-100 ug/m(3) 55,885 5,125 14,379 19,732 39,243 ------- ------- ------- ------- ------- 97,507 32,777 22,887 23,898 79,569 b. Compliance with 200 ug/m(3) > 100 ug/m(3) 41,622 9,340 13,569 11,958 34,867 50-100 ug/m(3) 55,885 5,125 14,379 19,732 39,243 ------- ------- ------- ------- ------- 97,507 14,465 27,948 31,690 74,110 c. Compliance with 100 ug/m(3) > 50 ug/m(3) 97,507 2,562 14,041 32,870 49,475 d. Compliance with 50 ug/m(3) < 50 ug/m(3) 97,507 498 5,373 22,729 28,599 Incremental Benefits b over a 18,312 -(5,061) -(7,792) 5,459 c over a 30,215 8,846 -(8,972) 30,094 d over a 32,279 17,514 1,169 50,970 c over b 11,903 13,907 -(1,180) 24,635 d over b 13,967 22,575 8,961 45,511 d over c 2,064 8,668 10,141 20,876

The figure summarizes the best point estimates of the ultimate effects of achieving various air lead compliance levels (a-d). The left side of the figure shows the results of parallel computations of the number of workers in the various blood lead level ranges. The right side of the figure shows the incremental benefits (reduction of the number of workers in each blood level range) of the "b", "c" and "d" compliance levels, compared to the baseline "a" compliance level which reflects the current distribution in the lead industry.

Assuming compliance with the present standard (the "a" compliance level), large numbers of workers could be expected to have potentially hazardous blood levels. At any one time, we anticipate that 32,777 workers would have blood lead levels over 60 ug/100 g, and 79,569 would have blood levels over 40 ug/100 g, in the absence of other remedial measures. Achievement of the "b" compliance level would reduce the number of workers over 60 ug/100 g, but would leave the number of workers in the 50-60 ug/100 g and 40-50 ug/100 g range substantially unchanged. Achievement of the "c" compliance level would be expected to reduce to about 2,500 the number of workers over 60 ug/100 g, and would be expected to produce reduction in the numbers of workers in the 50-60 ug/100 g blood lead level range to 14,000. The "d" compliance level would reduce the total number of workers over 40 ug/100 g to under 28,599, as compared to over 79,569 for the "a" scenario.

The incremental benefit of "d" over "a" in terms of the number of workers over 40 ug/100 g would be 50,970; for workers whose PbB levels would be over 60 ug/m(3), the benefit would be 32,279. These are clearly substantial reductions in the number of workers with excessive blood lead levels and would represent marked benefits to lead-exposed workers.

4. "Alternatives to the final PEL." During this rulemaking process, various parties advanced serious alternatives to the proposed OSHA standard. Since OSHA has adopted a PEL different from the proposal, this section will also discuss the proposed PEL of 100 ug/m(3) as an alternative to the final one of 50 ug/m(3). There were four alternatives proposed:

(a) "The LIA proposal," Adopt a standard which emphasizes biological indices and medical surveillance and which establishes an enforcement procedure directly utilizing these indices.

OSHA has decided to place primary reliance on a PEL which is based on environmental monitoring of air lead levels rather than relying on biological indices for the following reasons:

1. Evaluation of the industrial environment by proven industrial hygiene techniques is a direct measure of the sources of lead exposure, adequacy of control technology, progress in implementation of engineering controls, and in general represents a continual check on lead exposure. Since OSHA believes that control of an air contaminant should be accomplished at the source, environmental monitoring than is a direct measure of the control of lead exposure. Biological monitoring is designed to ascertain problems in individual workers and is an indirect measure of the control of lead. In this regard environmental monitoring is better suited to serve as a basis for enforcement.

2. Biological monitoring for compliance purposes is not feasible since there is no discrete value which could serve as the basis for citation. OSHA believes that based on consideration of health effects a PbB of 80, 70, or 60, ug/100 g would be excessive and would not protect workers' health adequately. It is infeasible to require controls to maintain blood lead levels for all workers at the desired 40 ug/100 g and below. Rather, when all controls have been implemented, 30 percent of all workers' PbB will range from 40 to 60 ug/100 g. Given the distribution of blood lead levels when compliance is achieved in a worker population, there is no discrete value which could serve as a maximum PbB. That is, OSHA believes that a PbB above 60 ug/100 g is excessive but a PbB between 40 to 50 ug/100 g may be the result of excessive exposure or it may represent the individual variation within a well controlled environment. Air lead determinations would differentiate between the two situations.

3. A biological standard is not only infeasible it would provide inadequate protection of workers. Excessive exposure to lead would not immediately effect excessive blood lead levels. In fact, some workers' blood leads might not rise to excessive levels for years, if at all, although their body burden would be increasing. Workers should not be expected to wait for protection until their blood leads become excessive. Air monitoring pinpoints overexposures immediately. This technique is preferable, therefore, for compliance purposes.

4. Worker groups uniformly and vehemently oppose biological monitoring for compliance purposes. OSHA views this opposition seriously since workers would be the subjects of a compliance program based upon biological monitoring and their voluntary participation in such an invasive process would be crucial to its success.

5. Industry's arguments that biological monitoring is preferred due to lack of an air lead-blood lead relationship are unsubstantiated. OSHA believes there is no doubt that an air to blood relationship exists and is best described in the CPA application of the Bernard model.

6. Although both biological and air monitoring are subject to errors, OSHA believes that the uncertainties associated with either measurement are not a sufficient basis for choosing one technique over the other. OSHA recognizes there are errors associated with air sampling, but nonetheless believes that evaluation of the plant environment is best and most directly accomplished through a comprehensive industrial hygiene survey as compared to biological sampling.

7. The record indicates that there are currently a significant number of industries which carry out biological monitoring. Given the current distribution of high blood lead levels throughout industry and the admitted lack of compliance with the current air standard OSHA has concluded there is little or no basis for accepting the asserted success of an enforcement mechanism based on future biological monitoring.

8. OSHA is concerned that a biological standard could impact negatively on workers with high blood leads and extended job tenure. Employers might terminate employment of these of these individuals to avoid citations for overexposure to lead. In addition, an employer could attempt to circumvent the standard by using respirators rather than implementing engineering controls. The use of respirators is not a satisfactory method for compliance. Indiscriminate use of respirators would be a confounding factor in ascertaining successful compliance with the standard.

Based on these considerations, OSHA will rely on determination of air lead level to ascertain compliance with the PEL.

b. "The Proposal -- 100 ug/M(3)." The proposal would have established a PEL for airborne concentrations of lead at 100 ug/m(3) as determined on an 8-hour time weighted average.

Based upon a thorough evaluation of the record, OSHA has reached the following conclusions which form the basis for establishing a PEL of 50 ug/m(3) instead of 100 u100g/m(3). The health effects data indicates that, to the extent feasible, blood lead levels should be kept at or below 40 ug/100 g. This contrasts with the proposal which set 40 ug/100 g as a mean, with 60 ug/100 g as a maximum. While feasibility limitations inhibit complete achievement of the goal of 40 ug/100 g as a maximum for all employees this goal can generally be achieved by setting the PEL at 50 ug/m(3). Nevertheless, it forms an important foundation for OSHA's decision to reduce the PEL to 50 ug/m(3). The CPA application of the Bernard model predicts a mean blood lead level of 34.6 ug/100 g at 50 ug/m(3) when compliance with the standard is achieved, compared to a mean PbB level of 40.2 ug/100 g at 100 ug/m(3).

The number of workers whose PbB levels were initially greater than 60 ug/100 g will be substantially reduced from 32,777 to 498 with compliance at 50 ug/m(3). For 100 ug/m(3), the benefits are also substantial, 32,777 to 2,562 with the incremental benefit for 50 ug/m(3) over 100 ug/m(3) being 2,064. There are 22,887 workers whose PbB are between 50 and 60 ug/100 g. Compliance with 50 ug/m(3) would reduce that number by 17,514, whereas at 100 ug/m(3), the number would be 8,846 with incremental benefit of 8,668 for 50 versus 100 ug/m(3). Between 40 and 50 ug/100 g there are 23,898 and compliance with 50 and 100 ug/m(3) results in a decrease at 50 ug/m(3) of 10,141 and increase at 100 ug/m(3) of 8,972 with a benefit of 50 versus 100 ug/m(3) of 10141. Lastly, there are 9,569 workers whose PbB levels are above 40 ug/100 g. Compliance with 50 ug/m(3) and 100 ug/m(3) respectively would reduce the numbers to 28,599 and 49,475 with an incremental benefit of 20,876 for 50 vs 100 ug/m(3).


                               SUMMARY

Incremental Benefit (by number of workers)
  50 ug/m(3) vs 100 ug/m(3)

Number of Workers removed:

>60 ug/100 g ................................................  2,064
50-60 ug/100 g ..............................................  8,668
40-50 ug/100 g .............................................. 10,141
>40 ug/100 g ................................................ 20,876

In summary, OSHA finds that 50 ug/m(3) will provide significantly increased protection to exposed employees over what would be achieved at 100 ug/m(3), and within the limits of feasibility provides substantial incremental benefits toward achieving a maximum of 40 ug/100 g.

(c) "The LIA Second Alternative - 200 ug/m(3)." The LIA has proposed that if OSHA decides to retain a single air lead exposure limit as opposed to a standard with primary reliance on biological monitoring, the limit should not be lower than 200 ug/m(3).

The evidence of adverse health effects cited in the proposed lead standard in this final standard demonstrates that a PEL of 200 ug/m(3) does not nor will not protect the worker in the lead industry from "material impairment of health or functional capacity." A PEL of 200 ug/m(3) would yield blood levels well above that which is deemed safe by OSHA in terms of both short and long-term exposure duration. Frank signs and symptoms of disease would be expected to occur at this level. The industry has argued that OSHA should not reduce the PEL from its current level at 200 ug/m(3) until compliance has been achieved at that level and medical evaluation has determined whether or not it is protective. OSHA believes the evidence already exists which demonstrates that 200 ug/m(3) is not protective and a delay in promulgating a new standard would place workers at severe risk to disease.

The benefits of compliance with 50 ug/m(3) versus the current level of compliance with 200 ug/m(3) were described in the benefits section and are substantial. The number of workers whose PbB levels are greater than 40 ug/100 g would be reduced from 79,569 to 28,599 and the number of workers whose PbB levels would be reduced below 40 ug/m g is 50,970. To summarize:


Incremental Benefit of 50 ug/m(3) vs. 200 ug/m(3)

Number of workers removed:

>60 ug/100 g ................................................... 32,270
50-60 ug/100 g ................................................. 17,514
40-50 ug/100 g .................................................  1,169
>40 ug/100 g ................................................... 50,970

It is important to note that the correct method of determining benefits is to compare a shift in the distribution of blood lead levels in the entire population. Comparison of the differences in average blood lead levels is irrelevant to an accurate understanding of the impact of the standard.

OSHA concludes that there are substantial benefits to be achieved from the promulgation of a 50 ug/m(3) standard and that the arguments set forth in favor of a 200 ug alternative are not compelling.

(d) 40 ug/m(3). The United Steel Workers of America proposed 40 ug/m(3) as an alternative to 100 ug/m(3) in the proposal.

OSHA has calculated the equilibrium distribution of blood lead levels assuming rigorous compliance with 40 ug/m(3) and has compared these results to a similar calculation for 50 ug/m(3). The results are as follows:


              BLOOD LEAD DISTRIBUTION (IN PERCENT)

_______________________________________________________________________

  >40 ug/100 g           40-50 ug/100g   50-60 ug/100g   >60 ug/100g
_______________________________________________________________________

40 ug/m(3)(24.2%) ....           19.9%            4%           0.3%
50 ug/m(3)(29.3%) ....           23.3%          5.5%           0.5%
_______________________________________________________________________

OSHA has determined that the incremental benefit of 40 ug/m(3) versus 50 ug/m(3) is negligible and in fact may be within the error of the measurements. While OSHA agrees with the goal that blood lead levels should be kept below 50 ug/100 g where possible, and in fact preferably below 40 ug/100 g, the levels required to achieve the latter value are clearly infeasible in the foreseeable future. Based on the conclusions OSHA believes the considerations which form the final standard are valid and the PEL of 50 ug/m(3) will be maintained.

C. MEDICAL REMOVAL PROTECTION

1. "Introduction." The final standard includes provisions entitled Medical Removal Protection. Medical Removal Protection, or MRP, is a protective, preventive health mechanism integrated with the medical surveillance provisions of the final standard. MRP provides temporary medical removals for workers discovered through medical surveillance to be at risk of sustaining material impairment to health from continued exposure to lead. MRP also provides temporary economic protection for those removed. Temporary medical removal is mandated for any worker having an elevated blood lead level at or above 60 ug/100 g of whole blood, or at or above 50 ug/100 g of whole blood averaged over the previous 6 months. These two ultimate blood lead level removal triggers are gradually phased in over a period of 4 years. Upon the effective date of the standard, temporary medical removal is also mandated for any worker found by a medical determination to be at risk of sustaining material impairment to health. In most temporary medical removals, the worker must be removed from any exposure to lead at or above the 30 ug/m(3) action level, with return of the employee to his or her former job status when the temporary medical removal is no longer needed to protect the worker's health. During the period of removal, the employer must maintain the worker's earnings, seniority and other employment rights and benefits as though the worker had not been removed.

2. "Importance of temporary medical removals." A central element of MRP is the temporary medical removal of workers at risk of sustaining material impairment to health from continued exposure to lead. This preventive health mechanism is especially well suited to the lead standard due to the reversible character of the early stages of lead diseases, and to the relative ease with which a worker's body may be biologically monitored for the presence of harmful quantities of lead. Temporary medical removal protects worker health both by severely limiting subsequent occupational exposure to lead, and by enabling a worker's body to naturally excrete previously absorbed lead which has accumulated in various tissues.

Temporary medical removal is an indispensable part of the lead standard for two significant reasons. Little margin for safety is provided by the final standard's 50 ug/m(3) permissible exposure limit, thus it is highly likely that some small fraction of workers (much less than 6 percent will not be adequately protected even if an employer complies with all other provisions of the standard. Temporary medical removal will be the only means of protecting these workers. Many years will be needed for some segments of the lead industry to completely engineer out excessive plant air lead emissions. During this time heavy reliance will have to be placed on respiratory protection -- a frequently inadequate means of worker protection. Again, temporary medical removal is essential for those inadequately protected. Temporary medical removal is a crucial element of the inorganic lead standard because it is the only control mechanism which can serve the two preceding functions. Temporary removal is not an alternative means for an employer to control worker lead exposure, however, but rather is a fall-back mechanism to protect individual workers in circumstances where other protective mechanisms were insufficient.

3. "MRP as a means of effectuating the medical surveillance sections of the lead standard." Temporary medical removals depend on voluntary and meaningful worker participation in the standard's medical surveillance program. Medical surveillance, a major element of the Act's integrated approach to preventive health, can only function as intended where workers (1) voluntarily seek medical attention when they feel ill, (2) fully cooperate with examining physicians to facilitate accurate medical diagnoses, and (3) refrain from efforts to conceal their true health status. No one can coerce these qualities of worker participation -- they will occur only where no major disincentives to meaningful worker participation exist. Absent these qualities of worker participation, medical surveillance cannot serve to identify those workers who need temporary medical removals, and consequently the overall protection offered by the lead standard will be diminished.

Participation in medical surveillance offered under the lead standard will sometimes prompt the temporary medical removal of a worker. Absent some countervailing requirement, removal could easily take the form of a transfer to a lower paying job, a temporary lay off, or even a permanent termination. The possibility of these consequences of a medical removal present a dramatic and painful dilemma to many workers exposed to inorganic lead. A worker could fully participate in the medical surveillance program and risk losing his or her livelihood, or resist participating in a meaningful fashion and thereby lose the many benefits that medical surveillance and temporary medical removals can provide. Convincing evidence presented during the lead proceeding established that many workers will either refuse or resist meaningful participation in medical surveillance unless economic protection is provided.

Much of the evidence in the lead proceeding documents the extent to which worker participation is adversely affected by the fear that adverse employment consequences will result from participation in medical surveillance programs. This problem was emphasized by the testimony of many workers and worker representatives. The problem was seen as widespread throughout industry, and as having already seriously affected participation in medical surveillance programs under several prior OSHA health standards which lack MRP benefits. Evidence concerning the issue of worker fear impeding participation was not confined to testimony from worker representatives, but was verified by a wide variety of experts and industry representative as well. Current industry practices are such that genuine economic disincentives to participation exist. These disincentives will be intensified by the new lead standard, particularly as a result of the temporary medical removal provisions. Finally, OSHA's adoption of MRP as a means of effectuating medical surveillance has been significantly influenced by experience gained under the Black Lung Medical Surveillance and Transfer Program created by Section 203 of the Federal Coal Mine Health and Safety Act of 1969. Experience under this program reveals the extent to which economic disincentives adversely affect participation even in medical surveillance programs where job transfer and limited economic protection are guaranteed. For all of the preceding reasons, MRP was included in the final standard as a means of maximizing meaningful participation in medical surveillance provided to lead-exposed workers.

4. "MRP as a means of allocating the costs of temporary medical removals." Temporary medical removal is fundamentally a protective, control mechanism, as is the elimination of air lead emissions through the use of engineering controls. The use of a temporary removal carries the possibility of dislocation costs to an employer through the temporary loss of a trained and experienced employee. And, a removed worker might easily lose substantial earnings or other rights or benefits by virtue of the removal. These costs are a direct result of the use of temporary medical removal as a means of protecting worker health. MRP is meant to place these costs of worker protection directly on the lead industry rather than on the shoulders of individual workers unfortunate enough to be at risk of sustaining material impairment to health due to occupational exposure to lead. The costs of protecting worker health are appropriate cost of doing business since employers under the Act have the primary obligation to provide safe and healthful places of employment.

One beneficial side-effect of MRP will be its role as an economic incentive for employers to comply with the final standard. Increasing public attention has been focused on the desirability of governmental regulations incorporating economic incentives to compliance, and though not adopted specifically to serve this purpose, MRP will nonetheless strengthen the protection afforded by the lead standard due to its inevitable impact on compliance. Employers who make good faith attempts to comply with the lead standard should experience only small numbers of temporary medical removals -- removals which can be absorbed by available transfer alternatives. Employers who make only cursory attempts to comply with the central provisions of the standard will find that the greater the degree of noncompliance, the greater the number of temporary medical removals and associated MRP costs. MRP will serve as a strong stimulus for employers to protect worker health, and will reward employers who through innovation and creativity devise new ways of protecting worker health not explicitly contemplated by the formal standard.

5. "Alternatives to MRP considered by OSHA." Before deciding to include MRP in the final lead standard, OSHA considered and rejected several possible alternatives. Mandating that employers compel all employees to participate in medical surveillance offered under the standard was rejected in part due to the fact that this step could not possibly assure the voluntary and meaningful worker participation upon which success of the standard's medical surveillance program depends. Mere participation is not an end in of itself. For example, no degree of compulsion can prevent workers from obtaining and misusing chelating agents so as to yield apparently low blood lead level results. No degree of compulsion can force workers to reveal subtle, subjective symptoms of lead poisoning which a physician needs to know as part of an adequate medical history.

In addition, OSHA declined to mandate worker participation in medical surveillance due to the substantial personal privacy and religious concerns involved in health care matters. Governmental coercion in this sensitive area would prove counterproductive to the goal of meaningful worker participation. Finally, the foregoing arguments against mandatory participation arise irrespective of whether or not MRP benefits are provided to removed workers. Thus, mandatory worker participation with MRP is no more satisfactory an alternative than mandatory worker participation without MRP.

A second alternative rejected by OSHA was to mandate that temporary medical removals occur only at the election of individual workers at risk of sustaining material impairment. Workers under this condition should have no reluctance to participate in medical surveillance since they would control the consequences of participation. This alternative would merely inform workers of their health status without providing affirmative protection to those who need it. Workers who should be removed would far too often choose not to be in the absence of MRP economic benefits, and employers would even be prevented from utilizing removal in situations where it was imperative. These results are inconsistent with the preventive purposes of the Act, and thwart the level of health protection which temporary medical removals can proved.

A third alternative rejected by OSHA was to permit the use of respiratory protection in lieu of temporary medical removal. OSHA rejected this alternative because of the inherent limitations of respiratory protection. The need to temporarily remove a worker from lead exposure is a matter of medical necessity. Relying on a respirator to protect a worker from exposure beyond such a point is unacceptable in light of the numerous inadequacies of respiratory protection. OSHA does not intend, however, to preclude the use of respirators where appropriate as one means (in conjunction with other industrial hygiene measures) of seeking to assure in advance that no worker need ever be removed. The need to temporarily remove a worker due to medical reasons will rarely arise without advance warning, thus providing an advance opportunity to use respiratory protection where appropriate. If respiratory protection proves effective in practice, then there will be no need to temporarily remove a worker.

6. "Feasibility." MRP as structured in the final standard is a feasible regulatory device. Elevated blood lead levels will in practice be the primary basis for the temporary medical removal of workers. Blood lead level removal triggers are phased in over a 4-year period as follows: (1) Beginning upon the effective date of the standard, the temporary medical removal of employees having blood lead levels at or above 80 ug/100 g of whole blood; (2) beginning 1 year after the effective date of the standard. The temporary medical removal of those having blood lead levels at or above 70 ug; (3) beginning 2 years after the effective date of the standard, the temporary medical removal of those having blood lead levels at or above 60 ug, and (4) beginning 4 years after the effective date of the standard, the temporary medical removal of those having average blood lead levels over the past 6 months at or above 50 ug. This 4-year phasing in process has been designed such that employers will have a reasonable opportunity to reduce their current employees' blood lead levels before particular blood lead level removal triggers come into effect.

Employers who comply with the new standard should experience few temporary medical removals, and thus a minimal economic impact from MRP. The gradual phasing in schedule will enable employers to structure their production operations so that transfer opportunities are provided to all removed workers. Four years will allow collective bargaining relationships to be altered if necessary so that all removals can be smoothly accommodated. Once MRP has been fully phased in and employers are fully in compliance with the new standard, only a small percentage of the exposed work force (much less than 6 percent should need temporary medical removals at any point in time. With experience, employers should acquire the ability to preclude even most of these temporary medical removals by removing sources of lead exposure which are causing the blood lead levels of particular workers to climb toward a removal trigger.

OSHA anticipates no substantially greater impact of MRP upon small employers than upon large employers. The lead record rejects any suggestion that small companies by virtue of size are incapable of protecting worker health. And, the level of health protection an employer provides, not size, will be the prime determinant of an employer's MRP costs.

7. "Temporary medical removal and return criteria." The ultimate blood lead level removal criteria derive from the conclusion that long-term blood lead levels in excess of 40 ug/100 g of whole blood must be avoided. Removal at a blood lead level of 60 ug is mandatory since this level will invariably represent numerous months of a blood lead level in excess of 40 ug during the overall period of absorption up to 60 ug and excretion down below 40 ug. Removal when an average blood level over the past 6 months is at or above 50 ug is required since this long-term average indicates a worker's blood lead level is either steadily increasing above 40 ug or has stabilized appreciably above 40 ug. Blood lead level measurements have a significant inherent measurement variability. To reduce the impact of this factor, both the temporary removal and return of workers due to elevated blood lead levels are based on the combined results of at least two independent measurements.

The standard provides that the return of a worker removed due to an elevated blood lead level to his or her former job status is also governed by the worker's blood level. During the years that the ultimate removal criteria are being phased in, the return criteria have been set to assure that a worker's blood lead level has substantially declined during the period of removal. A worker removed due to a blood lead level at or above 80 ug must be returned when his or her blood lead level is at or below 60 ug/100 g of whole blood; if removed due to a level at or above 70 ug, return shall follow when a level of 50 ug/100 g of whole blood is achieved. Once the ultimate removal criteria have been phased in, return depends on a worker's blood lead level declining to 40 ug/100 g of whole blood.

The standard requires that an employee be temporarily removed from lead exposure whenever a final medical determination results in a medical finding, opinion or recommendation that the employee has a detected medical condition which places the employee at increased risk of material impairment from exposure to lead. The term "final medical determination" refers to the outcome of the multiple physician review mechanism, or alternative medical determination mechanism, used pursuant to the medical surveillance provisions of the standard. Temporary removal based on medical determinations is included in MRP as a necessary complement to removal based on elevated blood lead levels. During the phasing in of MRP, workers experiencing adverse health effects from lead absorption deserve a temporary medical removal despite the fact that their blood lead levels do not yet require a removal. Even after MRP has been fully phased in, situations may arise where lead poisoning occurs in a worker having a blood lead level below the removal criteria, or a worker may acquire a temporary non-worker-related medical condition which is worsened by lead exposure. In addition, temporary medical removal may in particular cases be needed for workers desiring to parent a child in the near future or for particular pregnant employees. Some males may need a temporary removal so that their sperm can regain sufficient viability for fertilization; some women may need a temporary removal to slightly lower their blood lead levels so that prior lead exposure will not harm the fetus.

A worker removed as a result of a physician determination must be provided reasonable follow-up medical surveillance during the period of removal. The worker must be returned to his or her former job status when a final medical determination indicates that the employee no longer has a medical condition which places the employee at increased risk of material impairment to health from exposure to lead. The standard does not explicitly define the phase "material impairment to health" due to the innumerable contexts in which the temporary medical removal of a particular worker might be appropriate. Application of this phrase in a manner consistent with sound medical practice will result from the standard's physician determination mechanisms.

8. "Removal from work at or above the action level." In most cases where a worker is removed due to an elevated blood lead level or a medical determination, the standard provides that removal be from work having an exposure to lead at or above the 30 ug/m(3) action level. Work having an exposure to lead at or above the action level refers to the worker's daily 8-hour time weighted average (TWA) exposure to lead. As in all cases where the term "action level" is used, exposure is to be computed without regard to the use of respirators. This job placement limitation for most removals was based first on the need to assure that a worker not be removed to work having lead exposure high enough to further increase risks to health. The second reason for this limitation was to assure that a worker be removed to work having lead exposure low enough to enable the gradual excretion of excess lead so as to permit return of the worker to his or her former job.

During the first year following the effective date of the standard, however, workers removed due to blood lead levels at or above 80 ug need only be removed from work having a daily eight hour TWA exposure to lead at or above 100 ug/m(3). During the second year following the effective date of the standard, workers removed due to blood lead levels at or above 70 ug need only be removed from work having a daily eight hour TWA exposure to lead at or above 50 ug/m(3). These criteria were chosen consistent with the goal of effecting moderate worker blood lead level declines during the first 2 years of the standard's effect, while at the same time providing employers an opportunity to comply with the new lead standard and thereby avoid substantial MRP costs.

OSHA recognizes that situations may arise where removal to lead exposure just below the action level is inadequate to protect worker health. These situations can and should be dealt with on an individual basis in the course of a thorough medical examination conducted pursuant to the standard. The standard implies no unnecessary restriction on a physician's ability to recommend individual actions more protective than the standard's requirements. The standard does, however, embody the judgment that, at a minimum, all removed workers must be removed from work having an exposure to lead at or above the action level.

9. "Return of an employee to his or her former job status." The standard provides that once a period of removal or limitation has ended, an employee must be returned to his or her former job status. Former job status refers to the position the worker would likely be occupying if he or she had never been removed. If, but for a temporary medical removal, a worker would now be working at the same position held just before removal, then the employer may return the worker to that job. Otherwise, the employer may return the worker consistent with whatever job assignment discretion the employer would have had if no removal had occurred.

10. "The implementation of temporary medical removals." It is OSHA's intention that employers implement each temporary medical removal in a manner consistent with existing collective bargaining agreements. MRP is meant to override existing contractual obligations only to the extent that specific contract provisions directly conflict with the terms of MRP. MRP has been structured to guarantee maximum employer flexibility in effectuating MRP while minimizing the possibility of conflicts with existing collective bargaining agreements or other relationships. The standard does not specify what an employer must do with a removed worker; practically any action is permissible provided the worker is not exposed to lead at or above the action level. In most cases OSHA expects that a removed worker will be transferred to a low lead exposure position during the period of removal. OSHA intends that these transfers be to work that the employee is capable of performing and which is located in the same geographical area as the employee's normal job. Alternatively, the worker might work shorter hours at his or her normal job such that the time weighted average exposure is below the action level. The worker might even be temporarily laid off or arrangements might be made for the removed worker to temporarily perform comparable work at a non-lead-related facility. OSHA's intention is that the choice between these or other alternatives be a prerogative of the employer unless this flexibility is altered by some countervailing obligation. A removed worker is provided no automatic right to veto an employer choice which meets the standard, but similarly, the standard provides no right for an employer to simply override existing contractual commitments to either removed employees or to other employees.

Arguments have been made that MRP poses major conflicts with existing collective bargaining relationships. To the extent conflicts exist, they should be easily resolved during the lengthy phasein period for MRP. Worker transfer programs with economic protection have had longterm use throughout industry in a variety of contexts. These many programs have apparently melded quite will with collective bargaining relationships, and there is no evidence which suggests that the implementation of MRP will proceed any differently.

The mechanics of each temporary medical removal is a matter for the employer, the removed employee, and his or her collective bargaining representative, if any work out in the context of existing relationships. Some employers and unions may decide to modify their contractual agreements to specify how each removal will be accomplished, and the 4-year period during which MRP is phased in will provide ample opportunity for modifications to be made.

11. "Employer flexibility pending a final medical determination." In some instances a dispute may arise between an initial physician, chosen by an employer, and a second physician, chosen by the employee, as to the appropriateness of removing or returning a particular worker. Pending the outcome of the standard's physician review mechanism, the standard provides that an employer may act in a manner consistent with the medical findings, opinions or recommendations of any of the physicians who have examined the employee, with two exceptions. First, if an employee was removed or limited as to exposure to lead due to a final medical determination which differed from the opinion of the examining physician chosen by the employer, then the return of the worker (or the removal of limitations placed upon the worker) must be delayed until after a final medical determination has been reached on these issues. The second exception applies to situations where an employee has been on removal status for the preceding 18 months due to an elevated blood lead level, and a medical determination is being obtained as to continued removal of the worker. In this very limited instance the standard requires that the employer maintain the status quo -- i.e., removal -- until the full physician review mechanism has had an opportunity to form a final medical determination concerning the employee.

12. "Definition of MRP benefits." The standard requires an employer to provide MRP benefits to a worker on each occasion that a worker is removed from exposure to lead or otherwise limited. This requirement is defined as meaning that the employer must maintain the earnings, seniority and other employment rights and benefits of a worker as though the worker had not been removed or otherwise limited. In most cases this will simply mean that an employer must maintain the rate of pay of a worker transferred to a low-lead-exposure job. The standard, however, uses the all-encompassing phase "earnings, seniority and other employment rights and benefits" to assure that a removed worker suffers neither economic loss not loss of employment opportunities due to the removal. The standard explicitly requires that an employer maintain the seniority of a removed worker due to the crucial role that seniority rights might play in defining a worker's economic benefits. In addition, the standard by implication rejects industry suggestions that the provision of MRP benefits should be contingent upon the employer's ability to locate an available transfer position. Such an available position precondition would end MRP's role as a means of effectuating meaningful participation in medical surveillance.

13. "Duration of MRP benefits." The standard requires that up to 18 months of MRP benefits be provided to a worker on each occasion that he or she is removed from exposure to lead. The prime determinant of this figure is the rate at which workers will naturally excrete lead once removed from significant exposure. The vast majority of removals will be of far shorter duration than 18 months, but some longterm leadworkers will likely require 18 months of removal.

14. "Employees whose blood lead levels do not adequately decline within 18 months of removal." The standard establishes special procedures to apply in those rare situations where an employee's blood lead level has not adequately declined during 18 months of removal. A medical examination must be made available to obtain a final medical determination as to whether or not the worker may be returned to his or her former job status. In some situations, continued removal may serve no major purpose since the damage done to the worker's body is beyond the point of correction. In this event a physician might permit return of the worker to his or her former job status provided the worker's blood lead level remains fairly constant. In other situations a physician might recommend several additional months of removal where a worker's blood lead level is continuing to decline toward an acceptable level. In rare situations a physician might determine after 18 months that a worker's body burden of lead is so high that the worker will never be able to safely return to prior exposure. All of the preceding situations can best be evaluated and resolved by a final medical determination obtained pursuant to the standard.

Where the worker may not yet be returned to his or her former job status, the employer must continue to provide MRP benefits until either the worker is returned to former job status, or a final medical determination is made that the employee is incapable of ever safely returning to his or her former job status. The standard also provides that if a final medical determination returns a worker to his or her former job status despite what would otherwise be an unacceptable blood lead level, than any subsequent questions concerning removing the worker again are to be decided solely by a final medical determination. Automatic temporary medical removal due to an elevated blood lead level is no longer afforded to such a worker.

15. "Follow-up medical surveillance during the period of employee removal or limitation." The standard provides that during the period of time that an employee is removed from exposure to lead or otherwise limited, the employer may condition the provision of MRP benefits upon the employee's participation in reasonable follow-up medical surveillance. The standard does not mandate worker participation in follow-up medical surveillance, but rather permits the denial of economic protection to those unwilling to participate in procedures necessary for MRP's smooth operation.

16. "MRP and workers' compensation claims." In rare situations, a removed worker might be eligible for temporary partial or total disability workers' compensation payments for lost wages. Existing industry practices formed the basis for provisions responsible to these situations. If a removed worker files a claim for workers' compensation payments for a lead-related disability, and an award is made to the worker for earnings lost during the period of removal, then the employer's MRP benefits obligation is reduced by that amount. MRP benefits must be provided pending disposition of any filed claim subject to a credit or payback once an award is finally made.

17. "Other credits." An employer should not have to provide MRP benefits which duplicate compensation which a removed worker is receiving from other sources for earnings lost during the period of removal. Accordingly, the standard explicitly provides that the employer's obligation to provide MRP benefits to a removed worker shall be reduced to the extent that the worker receives compensation for earnings lost during the period of removal either from a publicly or employer-funded compensation program, or from employment with another employer made possible by virtue of the removal.

18. "Voluntary removal or limitation of an employee." A final element of the standard with respect to MRP provides that where an employer, although not required to do so, removes an employee from exposure to lead, or otherwise places limitations on an employee due to the effects of lead exposure on an employee's medical condition, the employer shall provide MRP benefits to the employee. The purpose of this requirement is to avoid the possibility that some employers will attempt to evade the MRP program by voluntarily removing workers (without economic protection) shortly before the standard would mandate removal.

19. "Legal authority for MRP." The Occupational Safety and Health Act contains ample legal authority for the adoption of MRP as a preventive health mechanism. OSHA's legal authority to adopt MRP was perhaps the greatest source of controversy during the lead proceeding, with industry representatives uniformly arguing that no legal authority for MRP exists. It is true that the Occupational Safety and Health Act contains no language which either explicitly requires or expressly authorizes the inclusion of MRP in OSHA health standards. The legislative history of the Act reveals no evidence that Congress gave any consideration to the appropriateness of MRP as a protective health mechanism. Though these factors are important, they are by no means dispositive of the legal authority question. The Act does not constitute a rigid congressional codification of the only permissible devices OSHA can employ to reduce occupational injury and disease. Rather, the structure and specifics of the Act reflect the congressional decision to create an expert administrative agency with broad regulatory powers to fashion reasonable protective regulations concerning occupational injury and disease in light of agency experience and expertise. The legal authority issue depends on the purposes to be served by MRP, the extent to which MRP is a reasonable response to a genuine problem, and the extent to which MRP is consistent with the Act's grants of and limitations on rulemaking authority by OSHA.

As previously explained, MRP is a protective, preventive health mechanism carefully structured to (1) maximize meaningful participation in the standard's medical surveillance program, (2) facilitate the use of temporary medical removals, and (3) appropriately allocate the costs of temporary medical removals. These functions are all directly related to the Act's purpose articulated in section 2(b) "to assure so far as possible every working man and woman in the Nation safe and healthful working conditions * * *." MRP responds to genuine occupational health problems and substantially adds to the level of overall worker protection afforded by the final lead standard.

MRP flows directly from and is fully consistent with the Act's express language. Section 6(b) authorizes broad OSHA discretion in the promulgation of each occupational health standard, defined by section 3(8) as a "standard which requires conditions, or the adoption or use of one or more practices, means, methods, operations, or processes, reasonably necessary or appropriate to provide safe or healthful employment and places of employment." MRP meets this definition, and further satisfies the dictate of section 6(b)(5) that occupational health standards be based on "experience gained under this and other health and safety laws." MRP is also a regulatory device which addresses the Congressional directive in section 2(b)(5) that healthful working conditions be provided "by developing innovative methods, techniques, and approaches for dealing with occupational safety and health problems." OSHA's adoption of MRP is a direct result of the proven value of this protective mechanism, and by adopting MRP, OSHA is following the Congressional mandate in section 2(b)(4) that worker health be provided "by building upon advances already made through employer and employee initiative for providing safe and healthful working conditions." MRP is needed to meet section 6(b)(5)'s requirement that health standards be set to protect all workers over entire working lifetimes because without temporary medical removals, it is doubtful that compliance with the remainder of the lead standard could achieve this mandated level of protection. MRP is also needed to achieve the benefits of medical surveillance envisioned by section 6(b)(7), and section 8(g)(2)'s grant of general rulemaking authority provides additional support for MRP's adoption. The preceding statutory provisions demonstrate that Congress intended OSHA to have broad flexibility in mandating remedial measures, and that MRP resides well within the scope of the flexibility Congress afforded.

The legal sufficiency of MRP's adoption is strengthened by comparable medical removal and economic provisions contained in the Federal Coal Mine Health and Safety Act of 1969, amended by the Federal Mine Safety and Health Amendments Act of 1977. MRP was not considered by Congress during the passage of the OSH Act, but this is hardly surprising in view of the Act's expansive coverage of practically every industry in the country. Congress established a broad regulatory framework without attempting to identify and respond to individual problems of specific industries. The 1969 Coal Act, however, represents the culmination of decades of intense Congressional attention to one extremely hazardous industry -- coal mining. The 1969 Coal Act was a comprehensive response to coal mine hazards, including thirty statutory pages of specific health and safety regulations as detailed as any existing OSHA standard. In the context of its comprehensive review of coal mining, Congress considered the appropriateness of an MRP-type program with regard to coal mine workers pneumoconiosis. Congress went beyond merely authorizing the adoption of MRP in this context to explicitly mandate the adoption of a MRP program. Authorization to adopt MRP with regard to other forms of mining was provided by Congress in the 1977 amendments to the Coal Act. Thus, in both of the instances where Congress has considered the appropriateness of MRP in an occupational safety and health statute, Congress voiced approval of MRP. This clear Congressional approval of MRP programs is indicative of how Congress likely would have acted had MRP been considered during passage of the Occupational Safety and Health Act.

Contrary to various suggested arguments, MRP does not violate section 4(b)(4)'s mandate that health standards not act "to supersede or in any manner affect any workmen's compensation law or diminish or affect in any other manner the common law or statutory rights, duties, or liabilities of employers and employees under any law with respect to injuries, diseases, or death of employees arising out of, or in the course of employment." Section 4(b)(4) was addressed in the legislative history, and has been applied in case law to date, only as a means of either preventing private cases of action under the OSH Act, preventing federalization of state workmen's compensation law, preventing duplication of federal regulations, or preserving state regulatory authority over safety and health matters. MRP is unrelated to all of these policies, including the policy against federalization of state workmen's compensation law. MRP neither intends nor operates to define or expand state law in this area. To the contrary, if MRP as a preventive health mechanism succeeds as intended, there hopefully will be no occupational lead disease left for state workmen's compensation law to address. To the extent such a result constitutes a conflict with state law, it is fully intended by the Act.

Various legal arguments were also presented in the lead proceeding to the effect that MRP somehow impermissibly conflicts with federal labor law, and with the Equal Pay provisions of the Fair Labor Standards Act. Having researched and considered these arguments. OSHA finds them to be without merit.

D. FEASIBILITY

In setting standards for toxic substances, the Secretary is required to give due regard to the question of feasibility. Section 6(b)(5) of the Act mandates that the Secretary shall set the standard which most adequately assures employees' safety and health "to the extent feasible on the basis of the best available evidence." Additionally, in the development of occupational safety and health standards, "considerations shall be the latest available scientific data in the field, experience gained under this and other health and safety laws."

OSHA has developed a rulemaking record which has enabled OSHA to promulgate a final lead standard which it can confidently state is feasible for all affected industries. The final standard has a PEL of 50 ug/m(3) as an 8-hour TWA, which, within 90 days, must be met by any combination of engineering controls, work practices (including administrative controls), and personal protective equipment. Compliance with the PEL exclusively by engineering controls and administrative controls including work practices is required to be phased-in over time according to an implementation schedule. The schedule varies by industry on the basis of technological and economic limitations on each industry's ability to comply, and for five industries whose compliance period in the schedule exceeds 1 year, includes an interim exposure limit of 100 ug/m(3).

The rulemaking record is comprised of studies and assessments of technological feasibility, cost data on various items of compliance, and economic impact assessments from the public participants as well as OSHA consultants. Most of the evidence assessed the feasibility of compliance with the proposed 100 ug/m(3) standard although various alternatives received attention. On the basis of this information, OSHA has constructed a compliance scheme designed to provide optimal protection to workers, to allow for necessary technological change, and to encourage long run, cost-effective solutions to compliance problems.

In establishing the requirements of this standard and evaluating whether compliance is feasible. OSHA has identified affected industries and investigated potential compliance methods including the available technology in those industries. It has attempted to estimate the length of time necessary to implement the technology required, taking into account firms' need to plan, construct, test, and refine their efforts.

The implementation schedule also takes economic factors into account in that it incorporates time periods which OSHA expects will enable firms in each industry to comply with the standard without serious economic repercussions to the industry as a whole. Where specific costs of compliance would be assessed they are presented in the industry summaries.

1. "Technological considerations." In general, inquiry into technological feasibility is only relevant to compliance with the exposure limits in the standard. It is clear that compliance with the 50 ug/m(3) PEL will be immediately feasible insofar as the standard permits respirators to be used where the required engineering and administrative controls including work practices are not sufficient. The primary issue is whether the PEL and interim level can be achieved in the time set forth in the implementation schedule solely by engineering and work practices. OSHA has concluded that compliance in this manner is possible through the use of presently available process and control technology or foreseeable technological developments.

Testimony and comments from most of the engineers and industrial hygienists in addition to OSHA's past experience with other standards for toxic substances has led OSHA to conclude that rigorous and innovative application of known, conventional techniques for isolating workers from the sources of exposure to toxic substances will, in almost all cases, enable employers to comply with the standard. Compliance in this manner is predicted to be completed in 1 to 5 years depending upon the complexity and extent of change required.

In some cases where accurate identification of exposure sources is difficult or where conventional control techniques are ineffective, reliance on new technology (e.g., new types of control or process equipment or alterations to the production process itself) may be necessary.

OSHA has attempted to be sensitive to the complexities and various aspects of the process of technological change in its attempt to incorporate new technology into its compliance scheme for this standard. This has facilitated prediction of the kinds of technology likely to arise in response to the standard and the time period within which they can be expected, thus allowing OSHA to know, in general terms, what is feasible. It has also suggested different options as alternatives in designing the standard so as to achieve optimal compliance strategies in terms of protective capability and compliance cost.

The following is a summary of the discussion of the technological factors considered in the major industries affected by the standard. Attachment D to the preamble (feasibility) contains a full discussion of these factors including a process-by-process analysis of the problems raised and the range of possible technical solutions to those problems in the most impacted industries.

a. "Primary smelting and refining." The primary lead industry ranks fifth (after iron, aluminum, copper, and zinc) in tonnage of metals produced in this country. Four companies - ASARCO, St. Joe Minerals, Amax and Bunker Hill -- own the seven facilities that smelt and refine primary lead. Western smelters date from the early part of this century; smelters for the Missouri lead belt were built during the 1960's. An estimated 3,055 employees in the primary smelting sector are exposed to lead. (Ex. 26. p. 5-3.) Primary smelting involves three basic steps -- sintering, smelting, and refining. In sintering, a concentrate of galena ore (PbS) is mixed with fluxes and roasted to drive off sulfur dioxide. This operation produces "sinter," a mixture of lead, lead oxide, and slag, which is smelted by a blast furnace at temperatures above 2,000 deg. F. The blast furnace reduces the constituents of the charge (coke, fluxes, and recycled slag sinter) into molten lead and slag. Fifteen ton ladles on overhead bridge cranes transport the molten lead to open drossing kettles about 14 feet in diameter. These kettles rest in firebrick settings that keep the lead at the temperatures needed (700 deg. to 1,200 deg. F.) for drossing. During drossing, the molten lead from the blast furnace is stirred, and the impurities (dross) are skimmed. The impurities in lead ores vary. Colorado ore, unlike Missouri ore, has a high copper content. The lead is further refined through a softening process that removes antimony and other metals.

Because pyrometallurgy (the extraction of metal from ores by heat) requires extreme heat at variable temperatures, control of emissions in primary smelting has been difficult. For example, material that splashes or drips during transfer of molten lead collects and freezes at the rim and pouring lip of the ladle. These thick, lumpy accretions can interfere with a tight fit between hood and vessels. Ore with significant amounts of copper produces copper matte, which corrodes iron, steel, and most steel alloys.

Thus, the corrosive property of the molten metal has prompted the use of open vessels and crude mechanical methods. The nature and scale of primary smelting have made the application of standard engineering techniques difficult. While the problems are difficult, the hearing record indicates that, with new techniques and methods, they are surmountable.

After reviewing the record, OSHA has concluded that in all operations except perhaps maintenance work and where process upsets occur, the 100 ug/m(3) level is feasible within the 3-year time period in the implementation schedule through retrofitting and some modification of existing processes. This conclusion is not in agreement with the conclusions of DBA and lead industry representatives. (Ex. 355, pp. 122-123.) After reviewing all the exhibits and testimony, OSHA is convinced that the reason or this disagreement is not so much a matter of differing professional judgment in what could be achieved, but in the interpretation of the term "feasibility." Industry representatives' and DBA's claims of infeasibility of the 100 ug/m(3) level (and even the present 200 ug/m(3) standard) are, in part, based on the view that for an exposure level to be feasible it must be attainable immediately at all work stations at all times. (Tr. 3971-72; 796, 797.) This interpretation was rejected in SPI v. OSHA. (Vinyl chloride) and AISI v. OSHA (coke ovens). DBA and industry representatives also limited their considerations to retrofit technology only and did not generally consider technological change unless it had been proved successful and could be implemented immediately. (Tr. 5793; Tr. 796-97; Tr 872-73; Ex. 26, pp. 4-5, 4-8; Ex. 29(29A).) Long-run technological solutions were not considered, even those which may be more cost-effective. This creates an a priori limitation on the gamut of possible approaches to compliance.

OSHA has concluded that compliance with the PEL may require up to 10 years for this industry. Primary smelting is not generally regarded as innovative. Dr. First characterizes the history of technological change in this industry as conservative and having "a strong bent to make changes vary slowly and in small steps." (Ex. 270 p. 17.) Other limitations on the rate of change are the size and complexity of the hot metals operations in these plants.

Further, the degree of technological change necessary to achieve 50 ug/m(3) may require development and implementation of innovative technology, possibly including alternatives to pyrometallurgy. OSHA believes that the 10 years provided in the implementation schedule represent maximum flexibility for compliance by an industry which may need to rebuild in part or in whole to achieve a healthful workplace.

Hydrometallurgical production methods are likely to be commercially viable within the 10-year limit; however, less comprehensive forms of process redesign and/or adaptation of developmental projects discussed in the feasibility attachment on specific operations may prove to be sufficient. (Tr. 1463.) Witnesses at the hearing were optimistic about the development of new processes for primary smelting. Knowlton Caplan, president of IHE, while skeptical about the current technological feasibility of a 100 ug/m(3) standard, expressed faith in the future development of "more effective and less costly engineering systems." (Tr. 5723) Frank Block, research director at the Reno Metallurgy Research Center for the Bureau of Mines, described one such potential development, a hydrometallurgical method for recovering lead from galena concentrate. (Ex. 128; Tr. 3386-34-17.) This process does not involve any sintering or smelting and may require no refining. It leaches galena concentrate in a hot solution of ferric chloride to produce lead chloride, which, in turn, is electrolyzed to produce metallic lead. The new process generates no sulfur dioxide. It would be more economical than current techniques and could operate at smaller capacity. It could also be used with Missouri or Western concentrates.

b. "Secondary smelting and refining." Secondary smelters produce much of the lead used in the United States. The industry, however, is poorly defined. The estimated number of plants, for example, has ranged from 40 to 140 (Ex. 138D, p. 1). Secondary smelters recycle lead from discarded batteries and other waste materials. This recycling involves two phases: smelting of the old material to recover crude lead and, in some operations, refining of the crude lead to produce pure lead and alloys for reuse.

Secondary lead smelting plants take scrap lead material from many sources, but the majority (61 percent) comes from scrapped lead-acid batteries. Lead cable covers, linotype, and recovered fume and drosses are other major sources. Some scrap is reprocessed to remove lead from other materials. Battery plates and terminals for example, are mechanically separated, and lead-copper cables are heated to melt off the lead. Materials containing lead oxide may be processed through a blast furnace to reduce the proportion of oxide to lead metal. Lead from the blast furnace and scrap containing lead metal may be melted in refining kettles and treated by drossing to remove copper and other impurities.

Following the drossing, the lead may be "softened" by removing antimony that has been previously added to give the lead hardness and strength. This removal is done by air oxidation in a reverberatory furnace or by oxidative slagging with sodium dioxide or sodium nitrate fluxes. Once the lead has been refined to a desired composition, it is cast into various shapes or fabricated into wires, pipes, sheets, or solders. (Ex. 26, p. 5-29.) Approximately 4,400 workers in the industry are exposed to lead. (Ex.

26, p. 2-13) Exposure levels vary among different operations, with the highest occurring in blast furnace areas. DBA analyzed OSHA compliance data and found that prior to August 1976, 83 of 171 air lead samples exceeded 200 ug/m(3). Data after this date showed 102 of 129 air lead levels above 100 ug/m(3) and 87 of 129 above 200 ug/m(3). (Ex. 26, pp. 2-17, 2-18.) The rulemaking record contains uncontroverted evidence that exposures in secondary smelting operations can be controlled below the 100 ug/m(3) interim level. Based upon its study of seven representative smelters, Dr. Thomas Smith testified for DBA that compliance by secondary smelters with a standard of 100 was technologically feasible. (Tr. 798) One company, Keystone Resources, which operates four secondary smelters across the country commented that "our controls are such that we feel we could also meet the action level (50 ug/m(3)) specifications" (Ex. 3(39)). Before the implementation of engineering controls, average air lead at Keystone Resources was 1,036 ug/m(3). The controls reduced the average to 126 ug/m(3). (Ex. 452, p. A-137) The results of a recent OSHA inspection at another secondary smelter indicate that it is presently in compliance with the 100 ug/m(3) level. (Ex. 26, p. 5-38; Tr. 956.) Attaining these levels, however, may in a few instances require extensive modifications of current processes. IHE, in a study for the Lead Industries Association, analyzed one plant in detail and concluded that conventional engineering techniques alone could not control battery breaking or scrap and slag handling to 100 ug/m(3) airborne lead. (Ex. 138D, p. 8) DBA doubted that manual battery breaking, slag and scrap handling, and some maintenance operations could be controlled without process redesign. (Ex. 26, p. 5-29) The rulemaking record describes new approaches that may be necessary to comply with the PEL, Michael Varner, corporate manager for ASARCO's Department of Environmental Sciences, and Melvin First, a professor of environmental health engineering at Harvard, discussed the possibility of innovations in drossing, such as continuous vacuum drossing. (Tr. 2387-80; Tr. 6530-31.) Svend Bergsoe, president of Paul Bergsoe and Son of Glostrup, Denmark, described in detail his new technique for smelting scrap lead products. (Tr. 5142-5204.) His process eliminates one of the hardest to control processes, battery breaking, by using a new type of furnace that not only digests the entire battery, but also use the battery cases to supply 50 to 80 percent of the fuel required to run the furnace. (Tr. 5194.) In addition a flash furnace agglomerates the flue dust, and the process is entirely enclosed.

With the possible exceptions of installing afterburner and agglomeration systems on existing furnaces (Tr. 5177, 5192), the Bergsoe process would require construction of an entirely new smelting plant, estimated to cost $2.5 million for a 20,000-ton-per-year production, and would take 2 years for construction (Tr. 5192). This cost includes the scrap handling facility (Tr. 5199), furnace, afterburner, baghouse, refinery, and even canteen and washing facilities.

c. "Battery manufacturing." The battery industry is the largest single user of lead in the United States. The industry produces both SLI (starting-lighting-ignition) batteries and industrial batteries, although the latter accounts for only 7 percent of the industry's production. 138 firms operate 200 plants, which vary tremendously in size and capacity. On one hand, the seven largest firms operate nearly 70 plants and account of over 90 percent of the batteries sold. On the other, 95 battery plants employ fewer than 20 people. Of the 16,000 persons employed by the industry, approximately 12,800, or 77 percent, are exposed to lead. (Ex. 26 p., 5-42.) Manufacture of batteries begins with production of lead oxide, either by the Barton process, which oxidizes lead in the molten state, or more often, by the ball mill process, in which frictional heat generated by tumbling lead pigs or balls produces lead oxide. Lead oxide powder is mixed into a paste and pressed onto grids cast from lead. The pasted plates are cured, stacked by hand or machine, and connected with molten lead ("burned") into groups that form the individual cells of a battery.

All these processes, especially loading and unloading at each step, generate contamination. The racks that carry the pasted plates from one operation to another are additional sources of lead dust. Dust forms as well during reclamation of rejected grids, parts, and pasted plates, and during removal of plate groups from defective batteries.

The record indicates that in the battery industry available methods can control employee air levels of lead below 50 ug/m(3), as an 8-hour TWA, for all major processes. Indeed, more than 40 percent of employees exposed to lead in this industry may already have TWA exposures of less than 50 ug/m(3). (Ex. 26, p. 5-45.) Meier Schneider, an experienced industrial hygiene engineer testified that "with proper engineering control coupled with good maintenance and good work practices, proper design of process to minimize emissions, and education of workers and good hygiene that we can, today, achieve levels in the (work room) atmosphere of less than 50 micrograms per cubic meter of air. (TR. 2065-2066) In his study of 17 plants, Bill Thomas of CAL-OSHA concluded that "the general use of respirators should not be needed in a well-designed and managed lead storage battery plant." (Ex. 101A) Similarly, Caplan, testifying on a detailed study of 12 plants IHE did for the Battery Council International ("BCI"), concluded that "technically, if all the things that we recommend were done and well done, it is our opinion that we would be able to control to 100."

It is OSHA's judgment that these systems proposed by IHE, when combined with good work practices and administrative controls will be effective to control exposure below the PEL, primarily because they provide total control of the process and minimize the opportunity for fugitive emissions. As Dr. First stated, "The application of good control methods almost always results in air concentrations far lower than the standard for which they were designed". (Ex. 270, p. 19.) IHE's specifications are designed primarily for larger operations. They assume that production is continuous and that operators remain at each work operation for a full shift, assumptions that do not hold for small plants. Thus, the engineering controls designed by IHE will be effective but may not be appropriate for small plants. The record suggests that less complex controls may be feasible and effective for small plants. Good housekeeping appears especially important. Both Meier Schneider and Albert Stewart, an industrial hygienist who formerly conducted lead inspections for OSHA, testified that control costs might be held down by approaching problems on a case-by-case basis and by emphasizing the use of good housekeeping and techniques for handling materials along with imaginative engineering to minimize the need for ventilation. (Tr. 2057-2077.) Dr. Mirer, the UAW's industrial hygienist, noted that of 30 plants surveyed by the UAW, the one with the lowest lead exposures had only nine workers. (TR. 1007.) Testimony from operators of small battery plants also stressed good housekeeping and work practices. For example, Don Hull, president of Dynolite Corp., a plant that employs fewer than 20 people, testified that he gives priority to housekeeping and personal hygiene. (Tr. 1246; see also Tr. 3561.) When OSHA took a series of readings in his plant at the stations for grid casting, stacking, element assembly, battery assembly, and battery filling, only one reading at one location, element stacking exceeded 100 ug/m(3), and it was just slightly over, 110 ug/m(3). (Tr. 1247-48.) Some operations with high exposures are done only intermittenly in small plants. Small battery plants, for example, may paste plates only once or twice a week. (Tr. 3465; Tr. 1259) To meet the PEL as an 8-hour time weighted average, such plants may not need the same controls as a plant that pastes plates all day every day. In fact, alteration of production schedules or employee rotation may be effective. Employees in small plants do not work exclusively at one station. As Stuart Manix of Lancaster Battery Co. explained, "most people try to do a little bit of everything." (Tr. 3465.) Thus, rotation of employees to positions with higher exposures for less than 8 hours per shift may also reduce 8 hour TWA averages. That is, four employees could each work 2 hours pasting plates.

New approaches may also offer small plants an alternative to IHE's engineering controls. Two firms, APSEE, Inc., and Kermatrol, Inc., testified that they could provide the technology for compliance at sharply reduced costs.

The new approaches might aid larger as well as small plants in meeting the 50 ug/m(3) standard. Some operations in either large or small operations will quickly be able to achieve the 50 ug/m(3) standard. The UAW asserted that aggressive implementation of such conventional control techniques as enclosure, ventilation, and process redesign can achieve the 50 ug/m(3) level. (Tr. 5278.) At the same time, the UAW recognized that until innovative processes are introduced, some operations will require respirators as well as ventilation to meet the 50 ug/m(3) standard. (TR. 5053.)

d. "Brass and bronze foundries." The lead content of copper based alloys, i.e. brass and bronze, may amount to as much as 20 percent by weight of the metal core. (Tr. 2786) The lead content of copper based ingots averages 5 percent. (Ex. 26, p. 5-73.) Over 1620 foundries cast brass and bronze at least occasionally; in approximately 770 foundries brass and bronze are the primary raw materials. Most of these foundries are small, 75 percent employing fewer than 50 people. Although small, most of these foundries make a diverse range of products of varying price, size, and composition. (Ex. 26, p. 5-73.) An estimated 26,000 employees are exposed.

Exposure to airborne lead results from insufficient control of fumes from the melting or pouring of alloys. In copper-base alloy foundries, approximately 15 percent of the particulate matter in furnace stack gases from the melting of red and yellow brass is lead oxide, and up to 56 percent of the particulate matter has been shown to be lead oxide when the alloy has a high lead content. Any workers in the vicinity of the melting or pouring operation as well as employees working to operate or maintain baghouse dust collectors may be subject to inhalation of these lead containing fumes. Sources of airborne lead may also include areas where castings are cut or finished and areas where scrap is received or stored. Levels of exposure are highly variable and depend on the amount of general local ventilation, the lead content of the alloy, the type of furnace, and the quality of housekeeping procedures. (Ex. 26, pp. 5-73, 5-75.) The hearing record indicates that brass and bronze foundries can achieve an exposure level of 100 ug/m(3) within one year. DBA concluded that feasible engineering controls are available to met this level. (Ex. 26, p. 5-73, Tr. 800.) They found that most plants do not at present have enough control in effect. Significant improvements are necessary for compliance with the proposed standard. For example, half the plants currently do not use baghouses and the majority do not provide heated make-up air. Gary Mosher, representing the American Foundrymens Society, explained that "exhaust systems have been devised and designed that will close capture * * * fumes right at the ladle and the furnace." He further testified that such methods are effective in bringing exposure below 200 ug/m(3), but did not express an opinion as to whether such techniques are effective in bringing exposure below 100 ug/m(3). (Tr. 2801).

OSHA, however, has concluded that conventional technology in the industry has been shown effective for lowering exposures from melting and pouring to 100 ug/m(3). Refinement and development of these technological changes should permit, over time, compliance with the PEL. Examples of these controls include: (1) The adoption of electrical induction furnaces with local exhaust ventilation installed during the initial furnace installation; (2) covered ladles; (3) segregated melts; (4) use of the Hawley Trav-L-Vent; and (5) increased use of dilution ventilation and directional ventilation during pouring. Compliance will, of course, also require comprehensive housekeeping, maintenance employee training, work practices, and personal hygiene. Further, administrative controls such as worker rotation may prove effective in reducing exposures in many small firms.

e. "Pigment manufacturing." Of the 114 plants that manufacture pigments in the United States, approximately 25 produce pigments containing lead. Pigment products include red lead (or, litharge), lead sulfates, lead carbonates, lead silicates, lead oxides and lead chromates. Inorganic pigments are a prime component in surface coatings and important components in other products such as linoleum, rubber and plastics, inks, ceramics, and paper coatings. Litharge is used principally in the manufacture of products other than paint, i.e., ceramic glazes, batteries, glasses, and vitreous enamels. (Ex. 26, p. 5-92.) The number of production employees in lead pigment manufacturing is estimated to be 2,000. DBA's survey of several plants indicated that 90 percent of the workers were exposed to levels of lead above 100 ug/m(3). (Ex. 26, p. 5-93.) The manufacture of pigments involves a number of different processes.

Only pulverizing and grinding processes for reducing the particle size are common to all members in the class. Inorganic pigment manufacture is a combination of chemical-physical processes involving both wet and dry reactions, including precipitation, filtering, washing, fusing, calcining, etc. The processes may be carried out as a batch system, as continuous production, or as a combination of the two.

Pig lead is often the basic raw material in inorganic lead pigment. Litharge and other lead forms, however, are sometimes used. Because litharge is a powder, it presents the potential for lead exposures at every transfer point. Filtering, drying, grinding, sizing, grading, blending, and bagging are all considered to be areas of potential exposure to lead. Cross contamination between operations also occurs.

Most pigment plants are old. All but five plants visited by DBA were at least 50 years old. One plant was said to be 129 years old. (Ex. 26, p. 5-95.) Because of the age of the facilities, retrofitting may not achieve levels below 100 ug/m(3), although such methods have reduced air-lead levels to 200 ug/m(3). However, redesign of the process, including "total enclosure of certain steps and/or automation" is expected to be able to reduce levels to a 100 ug/m(3) level. (Ex. 26, p. 5-98.) The same conclusion applies to the 50 ug/m(3) PEL. As Dr. First explained, "every operation that can be mechanized and automated is capable of being enclosed by tight physical barriers and placed under slight negative pressure to prevent outleakage of dust or fume-laden air to the workroom." (Ex. 270, pp. 29-30.) While such technology may require time and money to install, it is available and adaptable to the pigment industry.

Using substitutes for lead pigments, such as organic pigments, would eliminate exposures. While substitutes may not exhibit all the properties of lead, such as resistance to corrosion and weathering, they would nonetheless be adequate in many cases. Such substitution would also reduce or eliminate exposures in all the industries that involve lead pigment -- wallpaper manufacturing, glove manufacturing, pottery manufacturing, ink manufacturing, paint manufacturing, shipbuilding, and automobile manufacturing.

f. "Other industries." For the 11 other industries that were discussed in the DBA report or its supplement (Ex. 65-B), technological considerations are detailed in the feasibility attachment. OSHA found the PEL to be generally feasible within 1 year from the effective date by use of engineering and administrative controls. For a few operations, particularly in the shipbuilding and automotive manufacturing industries, airline hoods or other supplementary personal protective equipment may be necessary on a periodic basis.

Other industries were assessed for technological feasibility in the Short report (Ex. 22). They were generally found to have very low lead exposure and any compliance activities will only require very simple engineering controls.

2. "Economic considerations." OSHA has attempted to determine, for all affected industries, the costs of compliance of the final standard and to assess the economic impacts in terms of plant closures, industry competition, product prices, employment, and other economic factors. In many respects accurate and reliable cost estimates were difficult to determine for several reasons. OSHA and industry consultants who performed economic impact analyses found it difficult to avoid various forms of "double counting" of costs. Almost all of the information came from the regulated industries unverified by objective sources, and financial data, necessary to analyze the impacts, were not made available by individual firms.

In attachment D to the preamble, OSHA has made a detailed examination of the cost estimates of its contractor (DBA) and those of the principal industry consultants (CRA). Differences in estimates are discussed and reconciled where possible. In several instances, OSHA has reduced the estimates where obvious methodological errors required that such revisions be made. It should be noted that both of these studies attempted only to assess the cost of reducing exposures, by means of retrofit technology, from current levels to the proposed 100 ug/m(3) standard.

OSHA has concluded that the record contained adequate cost information for most industries. In addition, review of the record revealed that compliance with levels below 100 ug/m(3) might, in several industries, require extensive technological development for which long periods of implementation time would be required, thus precluding meaningful quantification of cost. However, the record was sufficient to predict that compliance within the times given would not result in undue economic hardship on those industries. This impact analysis is based on the record evidence concerning the financial and technical resources available to the various industries, the certainty of product and factor (production inputs) markets, and the availability of most cost-effective alternative methods of compliance.

The implementation schedule, itself, represents a merging of both economic and technological factors used to evaluate feasibility. Firms can choose from an array of technical solutions over a time frame sufficient for long run economic optimization. Since all firms in each industry face the identical PEL and time constraints, the process of the internalization of the cost of compliance acts on the decision-making process of the firm and the industry in the same manner as any other market signal. Depending on how firms judge a number of long-run factors including product demand, amount of investment sunk in the existing physical plant and managerial expertise, and alternative rates of return available on the necessary capital, some firms may choose to exit the market and invest in alternative ventures. Of course, other firms with different long-run expectations may choose to enter the market.

A brief review of the major affected industries follows:

a. "Primary smelting and refining." In all operations, except perhaps maintenance work and where process upsets occur, compliance with the 100 ug/m(3) level of engineering controls and work practices is feasible within the 3 year implementation period through the use of conventional control techniques as well as some modification or existing processes. Attainment of the PEL may require the development and implementation of substantial technological change, possibly including alternatives to pyrometallurgy which are now in the experimental stage. Ten years for this goal is considered by OSHA to be sufficient to encourage commercially viable technological solutions for this industry.

Given the earlier discussion about the unreliability of cost estimates, OSHA has determined that the capital expenditure to meet the 100 ug/m(3) interim level is in a range between $32 million and $47 million (in 1976 dollars). The total annualized cost at the 100 ug/m(3) level is estimated to range between $11.927 and $15.641 million. After-tax cost, figured on the corporate rate of 48 percent, should then be between $6,202 and $8.133 million. Based on total 1975 industry production, this would be equivalent to $0.004 to $0.006 per pound. OSHA has reached the following conclusions regarding economic impact in this industry:

(1) The primary smelting companies will probably be able to raise the price of refined lead as much as 1 cent per pound in order to pass compliance costs to consumers of its product. This increase will be sufficient to cover the incremental costs of meeting the 100 ug/m(3) interim level. DBA and CRA concluded that it would not be possible for firms to increase the price of lead. CRA attributes this to the high elasticity of foreign supply (Ex. 127, pp. 2-51 to 2-56), and DBA concludes that high elasticity of the demand for lead will have the same effect (Ex. 26, p. 6-25). CRA's and DBA's conclusion is somewhat doubtful for several reasons. First, given OSHA's revision of estimated costs to the industry, the necessary price increase would be smaller than predicted by CRA and DBA. Second, the demand for lead in the long-run, as well as the short-run, will most likely be price inelastic, and finally, the foreign supply of refined lead will probably be relatively inelastic in the short-run, the significant period in which domestic producers could recapture a substantial portion of compliance costs. As to the long-run, several factors can and may operate to make the foreign response to changes in U.S. price indeterminate.

The demand for lead will probably be substantially price inelastic in the long run. CRA's studies over the past 10 years, Dr. Burrows' (of CRA) repudiation of Heineke's work (the basis of the DBA analysis), and OSHA's evaluation of Heineke's conclusions support this. Therefore, demand factors should not play a significant role in the industry's pricing decisions. With respect to supply, the factors affecting the long-run behavior of firms are numerous. The increasing cost of producing lead (absent new discoveries) may impact on foreign producers sufficiently in the short run to reduce the incentive to shift production to the U.S. market. Foreign governments may follow the U.S. lead and compel similar environmental and occupational health constraints on their industry. Trade barriers or trade agreements limiting foreign imports may be adopted.

These factors affecting supply are highly speculative and no firm conclusions can be drawn other than that foreign supply is probably price inelastic in the short run, thereby allowing a short-run price increase, and possibly inelastic in the long run if one or more of several possible factors materialize.

At least one major producer, Amax, is confident that the industry will be able to pass costs forward. They stated that the costs of the standard "would certainly add to the price of our final product which in turn will have to be passed on to the consumer." (Ex. 3(67), p. 5.) (2) Compliance costs can, in part, be shifted backward to suppliers of ore. CRA concluded that costs could be shifted, in part, backward onto suppliers through a reduction in the price paid for ores and concentrates (Ex. 127, Exec. Summ., pp. 8-10). DBA did not evaluate backward shifting of costs. The extent to which this could be accomplished minimizes the cost impact on the primary producers. OSHA has concluded that the limits on the backward shifting of costs are not as sever as indicated in the CRA analysis. The increasing price of lead has improved the marginal conditions attributed to several mines by CRA. Further, the incentive to ship aboard depends on foreign costs maintaining their present relationship to U.S. costs excluding OSHA impacts, a questionable assumption. Finally, OSHA believes that the differential can rise somewhat above the cost of transporting the ore to foreign smelters because of the obvious advantages of adequate U.S. smelting and refining capacity to the domestic mines.

(3) The industry has the ability to pass costs forward or backward sufficient not only to recover the cost of the 100 ug/m(3) interim level, but to assure that any likely cost associated with the PEL will not jeopardize long-run profitability. In the assessment of market power, OSHA disagrees with the conclusion in the CRA report. The difference is most apparent in the analyses of the non-Missouri operations of ASARCO. (Ex. 127, pp. 2-79 through 2-84.) CRA calculates the annual compliance cost of the proposed standard to these operations at $3.7 million or approximately 1 cent per pound of refined lead. They are aware that ASARCO had announced its intention to spend $55.2 million at El Paso and $32.2 million at East Helena to control air quality problems associated with lead productions. These capital costs, when analyzed, produce an additional 6.2-cents-per-pound expense to the company, almost one-third of the market price of lead used in the analysis. The CRA cost pass-back analysis limits ASARCO's recovery from the mines to a maximum of 2 cents per pound. Their elasticity analyses preclude any long-run price increase. They conclude that the incremental OSHA costs seriously jeopardize continuing operation of the ASARCO Western smelters and refinery since the air quality controls would seem to cost ASARCO 4 cents per pound out of profit. They attribute ASARCO's willingness to continue in business to the externalities of custom smelters which extract "metals such as silver, cadmium, bismuth, and selenium as well as the slag processing which improves the flexibility of the ASARCO system." (Ex. 127, p. 2-84) CRA makes no attempt to document this claim. It is obvious that ASARCO was willing to risk an enormous sum of money. Either they anticipated an ability to recover that long-run expense in terms of price increases or cost pass backs or some combination of both.

OSHA concludes that the segment of the primary industry claimed to be in the most financial trouble, the Western custom smelters, have sufficient market power to survive enormous increases in costs. The money scheduled to be spent on air quality problems may alleviate some occupational lead problems as well. More important, it is the most impressive possible statement of the perception of the long-run viability of the industry by the largest producer. Since ASARCO announced these commitments, the price of lead has nearly doubled.

(4) If primary smelting firms were forced to absorb all the costs of compliance in the short run, they would nevertheless remain profitable and competitive. To the extent that increased costs cannot be passed back to suppliers or forward to consumers, the primary lead producers must absorb them internally, i.e., pay for them out of profits. From the record evidence as a whole, it appears that each of the affected firms can shift or absorb compliance costs of the interim level and remain profitable and competitive. Of all the primary producers, only Bunker Hill's profitability is in question and the cost impact should be such that OSHA costs alone would not threaten the company's economic viability.

DBA's conclusions regarding Bunker Hill are misleading because its calculations are based upon cost estimates that are significantly overstated. The cost estimates it used for the Bunker Hill smelter show the impact on Gulf Resources to be a reduction in the rate of return on total assets from 13.34 percent to 6.28 percent. (Ex. 26, p. 6-13.) This, however, is based on compliance costs at least double those which OSHA has determined to be reasonable. Similarly, the percentage decrements for the other firms, St. Joe (1.56 percent), ASARCO (1 percent), and Amax (0.3 percent) would be even smaller if adjustments were made using the revised cost estimates. The same is true in the percentage decrements predicted for value of the firms' common shares. The result is that DBA's conclusion that Bunker Hill would have to shoulder an inordinate compliance burden compared to the other firms is weakened. Gulf Resources' return on assets will decrease more than the other firms', but it will still have a rate higher than ASARCO and Amax.

The steelworkers asserted that each of the four firms could pay for all the capital improvements estimated by CRA out of 1976 profits alone. (Ex. 343, p. 172.) Their calculations showed that compliance costs as a percentage of 1976 profits were as follows:


____________________________________________________________________

                                    Capital             Annual
       Company                        costs              costs
                                    (percent)          (percent)
____________________________________________________________________

ASARCO ..........................      45.6               11.3
Amax ............................       5.4                1.7
St. Joe .........................      15.4                4.5
Gulf Resource ...................      54.3               15.9
____________________________________________________________________

CRA evaluated each firm's profitability and their ability to shift costs back to suppliers of ore. They concluded that Bunker Hill, with the heaviest costs of compliance and little chance to shift cost back to suppliers, might prove uneconomical for Gulf Resources to continue to operate. Initially, production at Bunker Hill is expected to increase (Ex. 343, p. 173), thereby lowering the cost per pound, but more important, the cost attributable to the OSHA standard is less than 1 cent per pound. (0.95 cent by CRA's calculations.) This is only 0.23 cent in excess of the 0.72 cent per pound that CRA estimates Bunker Hill can pass back to the mines under the best conditions. (Ex. 127, p. 2-73.) Under the worst conditions, the differences would be 0.8 cent (Ex. 127, p. 2-74). The firm would have to absorb between $0.579 to $2.016 million in compliance costs.

Looking then at profitability, CRA concluded that if Bunker Hill was forced to absorb between $2.3 to $3.9 million, the consequences would be "severe." However, Bunker Hill's 1975 profit was $6.2 million. Its average profit between 1970 and 1975 was $10.664 million overall and about $5.332 million from lead operations. Absorbing costs of $0.579 to $2.016 million will cut into profits, but those costs are only 5 to 19 percent of the firm's average profits. This mitigates CRA's conclusion.

In fact, the decision of the management of Gulf Resources on whether or not to make the investment required at Bunker Hill will be determined by its assessment of the long-run profitability of the industry. Profits in 1975 were reduced because of production restrictions related to air quality problems since alleviated. Also, as noted earlier, the price of lead is almost double its 1975 level.

(5) If compliance costs reduced the profitability of Bunker Hill to a point where Gulf Resources decided to close its lead operations, the competitive structure of the primary sector would be largely unaffected. DBA stated it this way (Ex. 26, p. 6-26):

If one or more producers of primary refined lead should be forced to shut down lead refining operations, concentration in primary refined lead production could increase substantially. Such an event would no doubt facilitate cooperative behavior among the surviving primary lead producers. However, this probably would not affect significantly the nature of competition in refined lead.

The degree of concentration in primary refined lead production is already potentially high enough to achieve a joint monopolistic result as a consequence of the mutually recognized interdependence of the four large producers. This could occur without the necessity of resorting to overtly collusive conduct.

That this result is not presently attained is due to forces being exerted from outside the primary lead segment of the market, viz, from secondary lead, refined lead imports, and the threat of entry. These forces would still be operating no matter what the degree of concentration in primary refined lead. Thus the competitive situation probably would not be significantly affected even if the imposition of the proposed occupational lead exposure standard leads to a reduction of the number of firms engaged in primary lead production.

(6) The compliance schedule for meeting the 50 ug/m(3) standard assures economic viability.

The 10-year period set forth in the methods of compliance section is based primarily on technological factors. This time should be sufficient for any firm to completely rebuild an existing smelter (Ex. 3(103), p. 5) or to construct new capacity.

This extended compliance period also assures economic viability of the PEL. Production efficiencies may arise from new processes, such as hydrometallurgy, sufficient to offset EPA and OSHA costs. Retrofit technology may be refined that will effect control greater than now envisioned for existing equipment and thus lower long-run costs of compliance. DBA stated that "we can expect to see new, innovative and cost-effective compliance methods being introduced as a result of enforcement of the standard." (Ex. 26, p. 2-16.) The 10-year compliance time constitutes a planning horizon sufficient to allow all firms maximum flexibility in capital planning. OSHA believes the long-run outlook for the industry is favorable and there exists some combination of engineering controls and work practices, including administrative controls, which will permit all four firms to remain in the market. Because the economic and environmental conditions of the western smelters vary widely from those in Missouri and among themselves, OSHA has established a time frame designed to maximize the technological and economic options for the industry. This compliance period is sufficient to allow each firm the opportunity to assess the likely state of the market and to raise the capital necessary for conversions required by air and water quality standards, other OSHA standards, and the 50 ug/m(3) lead standard. OSHA has concluded that this flexibility is necessary for achieving the most cost-effective solution for the industry consistent with necessary worker protection.

(b) "Secondary smelting and refining." Compliance with the interim level in 3 years and PEL in 5 years appears feasible since extensive process modification as well as refinement of recent technological developments may be necessary for some firms. In addition, the Bergsoe smelting process, a cleaner, more fuel efficient smelting technology used for many years outside the United States, is available for either partial adaptation to existing facilities or total adaptation if new facilities are built. Construction of new plants employing this technology would take 2 to 3 years and may provide a more cost-effective alternative to present technology.

Capital costs for compliance by means of retrofit controls with the interim level have been estimated to range from $34.1 to $51.1 million. Pretax annualized costs associated with these estimates are $18.9 million and $28.5 million, respectively. After taxes, the figures range from $9.8 to $14.8 million. The annual cost of the best estimate is equal to $0.013 per pound of 1975 production.

The cost of attaining the PEL of 50 ug/m(3) cannot be ascertained precisely because the industry faces several options for long-run compliance. However, an upper limit (the cost of completely rebuilding the industry with the latest available technology) is determinable. To completely rebuild with the Bergsoe process would cost approximately $90.6 million excluding land costs.

OSHA has concluded that compliance with neither the 100 ug/m(3) nor the final PEL of 50 ug/m(3) is likely to have severe impacts in this industry. This is in general accordance with the views of CRA and DBA. Both predicted some closures from high-cost marginal operations but expected no drastic impact on the structure of this industry. DBA seemed to be somewhat more pessimistic about closure than the industry study. DBA noted that although concentration has been increasing (Ex. 26, pp. 6-6, 6-7), production within the industry is still not highly concentrated, primarily as a result of low entry barriers. Sources of scrap can be easily acquired and initial capital requirements are low. (Ex. 127, p. 1-29.) As a result, secondary producers have little control over prices, even in the short run, essentially following the market. (Ex. 26, p. 6-10.) They will be able to shift compliance costs forward onto product prices only if primary producers raise prices. OSHA has determined that the DBA impact assessment is faulty in two respects. First, DBA did not consider the possibility that primary smelters might be able to pass through some of the compliance costs and secondary smelters would benefit accordingly. More importantly, DBA did not analyze the ability of secondary firms to pass cost back to scrap dealers. CRA anticipates that the average compliance cost will be passed back and thus only firms whose costs exceed the average would have to absorb any compliance cost even absent a price rise.

These estimates make no allowance for the use of administrative controls which should bring further reduction from these estimates. Firms will be able to increase prices to the extent that the primary producers do so. However, at least the average compliance costs can be passed back to the scrap dealers. Thus only the highest cost marginal firms are likely to face a decision on whether or not to cease operations.

(c) "Battery manufacturing." Control of lead exposure for the more than 12,000 exposed employees in accordance with the implementation schedule for this industry is feasible through the use of conventional engineering and industrial hygiene techniques, although significant modifications may be required in the production process. Less complex, and less expensive compliance solutions appear to be possible for small producers, including the use of employee rotation.

OSHA estimates the capital cost of meeting the 100 ug/m(3) interim level to be in the range of $205.1 to $230 million with annualized costs of $25 to $28.1 million.

The battery industry is essentially an oligopolistic industry with a fringe of small independent producers who compete in regional or specialty markets (Ex. 26, p. 6-37). It is comprised of 138 companies who operate a total of 200 plants, but the 5 largest companies, who operate 55 plants having 78 percent of the total industry capacity, dominate the market. (Ex. 26, pp. 6-33, 6-37.) The seven largest companies operate 70 plants and sell 90 percent of all the batteries sold (Ex. 26, p. 5-42). It is also an industry that has been in the process of consolidation for many years. In the past 20 years the number of firms in the industry has steadily decreased from over 300 in 1954 (Ex. 127, p. 3-4) to just 138 in 1972 (Ex. 26, p. 6-33).

The questionable assumptions underlying the IHE report (the engineering which provided the basis for the cost estimates) lead to the conclusions drawn by DBA and CRA that approximately 100 small battery manufacturers would exit the industry as a result of the proposed standard. (Ex. 127, p. 3-53; Ex. 26, p. 6-24.) OSHA does not believe that the approximately 100 small plants will have to assume the magnitude of cost used by DBA and CRA because of the overestimation of costs by IHE, because the lead quantity in small plants is lower (Ex. 349, pp. 16-28), and because of several available low-cost compliance alternatives, discussed earlier, which are uniquely suited to small plants. In addition, some small manufacturers might take advantage of economics of scale by increasing production, e.g., expanding a one-shift operation to a two- or three-shift operation.

Some of these small firms will probably exit the market irrespective of the OSHA standard. There has been a trend in recent years of very small firms (95 firms have less than 20 employees and a total of 2 percent of the market) leaving the industry because of unprofitability. These firms have discovered shrinking markets for their products, and an inability to compete with larger companies because size is related to production efficiency. Most of the new plants in the industry have been quite large. (Ex. 127, pp. 3-6.) These factors are expected to continue to put severe stress on the small battery manufacturer without respect to additional costs due to OSHA regulations, and the consolidation trend is expected to continue.

OSHA has concluded that even if the questionable DBA and CRA prediction that approximately 100 small manufacturers would exit the market were true, the standard is nonetheless feasible for the battery industry.

Closure of 100 small businesses would have a minimal impact on the competitive structure of the industry. Thirty firms operating 100 plants will remain, and the capacity of the 7 largest firms, now 90 percent of industry capacity, will increase a few percent. Competition from the smaller firms has little or no effect on the price of batteries, which is set by the major producers, except in those "interstices of the market which the major producers do not choose to capture." (Ex. 349, p. 19; Ex. 26, p. 6-42; Ex. 127 pp. 3-7 through 3-9.) The small producers may set prices in small local markets where they supply retailers directly and take, in price, the equivalent of distributor markups or where special services (picking up old batteries, fast delivery, etc.) to the retailer allow price increases. (Ex. 127, p. 3-8.) Battery prices will increase as a result of the passthrough of compliance cost. The industry price setters, the five major producers, will have compliance costs of about $0.74 per battery, with an industry average of $1.11. (Ex. 127, p. 3-35.) CRA has estimated that a cost passthrough of $0.74 will result in a retail price increase, due to markups in the distribution chain, of about $1.75 per battery. (Ex. 127, Exec. Summ., p. 37.) This will allow small producers who enter the distribution chain at advanced stages to pass through costs of about $1.04 per battery (Ex. 127, Exec. Summ. p. 37.) except where they are not in competition with the major firms.

Closing of 100 plants employing 10 persons each would mean the loss of approximately 1,000 jobs. Compliance activities require additional manhours, however, and it is estimated that the net gain in employment, if production remains at the prestandard level, would be approximately 2,000 employees. Productivity, therefore, would decrease by just over 9 percent. The impact on wages would be small. (Ex. 26. p. 6-43 and 6-44.) OSHA's evaluation of the technology available to the battery industry indicates that compliance with the PEL may be achieved by the same types of technological changes required to achieve the interim level of 100 ug/m(3), although further refinement, additions, and modifications may also be necessary. The compliance schedule requiring engineering controls and work practices to be used to reach 100 ug/m(3) in 2 years and the PEL in 5 years is based on the time it should take to implement the relatively conventional control methods required. Large manufacturers should have little problem meeting the costs involved, especially since they will be able to pass on all of the increased costs of production to consumers. For smaller manufacturers, OSHA has concluded that simple and inexpensive approaches can be effective in many situations, thereby drastically decreasing their inordinately excessive estimates of compliance cost. Where capital acquisition problems are encountered in meeting the implementation schedule, the flexibility in the compliance scheme for the standard should, under certain conditions, enable employers to spread compliance costs over 5 years.

(d) "Brass and Bronze Foundries." Compliance with the interim level of 100 ug/m(3) in 1 year is feasible in this industry with presently available technology, while compliance with the PEL may require some further development and refinement of the same technology.

Cost estimates for compliance with the interim level are $161 million for capital expenditures and $41.2 million in after-tax annualized cost. Costs of compliance will be passed on to the purchasers of castings, and DBA estimates that price increase would be equivalent to about $0.16 per pound of casting. This assumes that industry profit rates will be maintained since it is double the price necessary for full cost recovery. Some small firms with higher than average costs of compliance may leave the industry thereby reducing competition, and since substitutes for brass and bronze castings exist for some uses total industry output may fall. The industry association which testified at the hearings did not plead economic hardship.

(e) "Pigment manufacturing." Control of employee exposure in pigment plants to comply with the implementation schedule will probably require extensive modification of the present production processes. Substitution of other materials for lead is also possible for some uses of pigment. Cost estimates for this industry for the interim level are between $17.6 million and $21.1 million and $6.4 million in annualized costs. These costs are for retrofit technology which may not be adequate to comply with the PEL. If compliance with the PEL requires the redesign of the production process, the capital costs for the industry may be in the area of $109 million after-tax annualized costs of $21.8 million.

DBA concluded that almost all costs of production would be passed on to the consumers, and competition in the industry would decrease slightly as marginal firms exit. The DBA analysis was based on estimates of the cost of totally rebuilding the industry ($109 million -- capital; $14.8 million -- annual). Given the product substitution option, OSHA doubts that such estimates would ever be realized. However, if such sums are ever spent, they would be expended to comply with the PEL over a 5-year period. OSHA's revised estimates of the cost to achieve the 100 ug/m(3) interim level would require a price increase of 1.7-3.7 percent instead of the DBA prediction of 16.6-21.6 percent. This would substantially mitigate the impact on marginal firms.

(f) "Other industries." At least 33 other industries have been identified as having some lead exposure. In almost all cases control of lead levels below the PEL should be feasible within 1 year using conventional methods, but in some operations, such as solder grinding and paint spraying, elaborate personal protective equipment may be necessary to comply with the PEL.

(g) "Aggregate economic impacts." While the costs of compliance are significant for some industries and the employment impacts may have regional significance, the aggregate impacts are minimal. The effect of costs associated with the interim level is estimated to increase the Consumer Price Index by only 0.02 to 0.03 percent.

[43 FR 52952, Nov. 14, 1978]

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