Regulations (Preambles to Final Rules) - Table of Contents Regulations (Preambles to Final Rules) - Table of Contents
• Record Type: Air Contaminants
• Section: 5
• Title: Section 5 - V. Summary of Commenters' Responses to NPRM Questions

V. Summary of Commenters' Responses to NPRM Questions

In the preamble to the proposed rule (53 FR 20961), OSHA asked interested parties and the public for information related to 27 questions. These questions addressed a large number of issues, such as the scope of the rulemaking, the appropriateness of the proposed exposure limits, the availability of feasibility information for particular substances, the definition of material impairment of health, and the availability of engineering and cost data relevant to this rulemaking.

Many commenters (see, for example, Exs. 3-593, 3-660, 3-741, 3-744, 3-891, 3-896, 3-1095, 3-1161, 8-16, 8-19, and 8-47) submitted responses to the questions raised by OSHA. Of these commenters, most chose only to answer selected questions, while NIOSH provided answers to all of the issues raised. The responses of commenters to each of the questions specifically asked in the preamble to the proposal are summarized below. In addition, many participants addressed some of the issues raised by these questions in their comments on the health effects or feasibility of individual substances. These comments are addressed in connection with the preamble discussion for each substance. More detailed responses to some of these comments are discussed in other sections of the preamble, in connection with the health and feasibility discussions for specific substances.

1. Are substances included which should be excluded from this rulemaking?

Several commenters (See, for example, Exs. 3-593, 3-891, 3-896, 3-1095, and 8-47) responded to this question. There was widespread support for OSHA's selection of substances for regulation. For example, the Dow Chemical Company (Ex. 3-741) "supports the PEL project in changing outdated PELs." Several commenters, however, requested that certain aspects of the proposal be modified.

For example, Susan Kernus, Manager of Government Affairs for the Synthetic Organic Chemical Manufacturers Association (SOCMA), stated:

We do not believe any substances included in the proposal should be excluded, but we strongly object to the adoption of [NIOSH] REL's. We recommend that ACGIH TLV's be adopted for these substances....(Ex. 3-891, p. 6).

George Talley and Michael Garcia, industrial hygienists with the Los Alamos National Laboratory, argued that recommended exposure limits (RELs) with "insufficient or old...data" should be deleted, as also should substances for which sampling and analytical methods are unavailable (Ex. 3-1095).
Commenting for the Chevron Corporation, Stanley Dryden stated:
We support the adoption of the ACGIH Short-Term Exposure Limits (STELs) that were established on the basis of careful review of documented short-term health effects. However, for several substances the proposed STELs are not adequately justified.... We recommend that the proposed STELs be removed from this rulemaking except where there is clear evidence that the STEL is required to protect against a material impairment of health (Ex. 3-896, p. 3).

U.V. Henderson, Jr., Director of Environmental Affairs for the Texaco Company, endorsed OSHA's choice of regulatory candidates by stating: "No substances are included in the listings which should be excluded from rulemaking" (Ex. 3-593). In response to this question, NIOSH expressed support for the inclusion of the proposed substances but urged OSHA to take further action "immediately upon completion of this rulemaking...to establish PELs for all substances that are excluded from this rulemaking" and for which NIOSH has made a recommendation to OSHA (Ex. 8-47, p. 17). NIOSH stated that OSHA should initiate "consolidated rulemaking ... to adopt all NIOSH RELs pending [the initiation of] chemical-specific Section 6(b) rulemaking...." (Ex. 8-47, p. 17).

The support voiced by these commenters is gratifying to OSHA and increases the Agency's confidence that the substances selected for this generic rulemaking are both necessary and appropriate. The ancillary issues raised by these commenters, such as the appropriate basis for short-term exposure limits, the use of ACGIH TLVs in lieu of NIOSH RELs, and the initiation of other rulemakings in the future, are addressed in other sections of this preamble, e.g., Section VI.C.17 (STELs), Section VI on the Agency's methods of selecting exposure limits, etc. Readers are referred to these sections for a detailed discussion of the record evidence on these topics.

2. Is additional health and feasibility documentation available relative to the proposed PELs beyond that described in the preamble?

Several participants (see, for example, Exs. 3-741, 3-891, 3-1043, and 8-47) specifically responded to this preamble question. (There were of course many responses directed to health effects or feasibility issues on specific substances; these are presented in the discussions for individual substances (see Section VI).) The Synthetic and Organic Chemical Manufacturers Association (SOCMA) reported that it does not possess additional data but has requested its members to submit to the docket any information available to them (Ex. 3-891). Richard Olsen, project manager for the Dow Chemical Company, noted his company's support for the PEL project but stated that Dow was limiting its submission of additional data to certain substances, such as styrene and those chemicals for which OSHA proposed the adoption of NIOSH RELs. According to Mr. Olsen, "Feasibility documentation is not readily available in the time allowed to prepare this submission because it resides mainly with our customers." However, Dow did ask several of its customers to submit feasibility information to the record (Ex. 3-741).

The American Federation of State, County, and Municipal Employees (AFSCME) stated that OSHA had not evaluated 14 other lists developed by professional organizations and foreign bodies" (Ex. 3-1043). AFSCME is of the opinion that OSHA should have started its analysis with the most protective standard.

NIOSH commented that additional health and feasibility data pertaining to these substances and affected sectors are available and urged OSHA to consider criteria documents, health hazard evaluations, current intelligence bulletins and other NIOSH publications when developing the final rule. NIOSH also noted that several foreign governments (e.g., Germany, Sweden, West Germany), organizations (e.g., the American Industrial Hygiene Association, the International Labour Organisation), and research groups (e.g., the National Toxicology Program, the International Agency for Research on Cancer) have provided extensive toxicity information (Ex. 8-47, pp. 17-18).

In the proposal, OSHA relied extensively on the health effects information made available by these and other organizations and individuals; the reference list for the health effects section of the proposal alone included more than 1,000 citations to the toxicological literature. In the development of the final rule, OSHA has gone beyond this initial list to include hundreds of additional citations and has additionally performed a thorough analysis of all data submitted to the rulemaking docket.

OSHA appreciates NIOSH's submission of data to the record and the efforts of SOCMA and the Dow Chemical Company to obtain feasibility data from their members and customers, respectively. Information submitted by NIOSH and these individuals is discussed in other portions of this preamble in connection with the specific feasibility concerns and health effects issues raised by these commenters.

3. Are substances included in this rulemaking used in industries other than those described in the preamble? and

4. Are substances included in this rulemaking used for purposes other than those described in the preamble?

NIOSH (Ex. 8-47) responded to these two questions together by noting that it has submitted to the record a printout of the complete NIOSHTIC data base file. This information often contains industry-specific data on exposures, operations, and controls, and OSHA has analyzed this information as part of this rulemaking. No other commenters provided responses specifically to these questions, and OSHA therefore believes that the proposal and its appendices accurately identified both the major chemical-using industries by Standard Industrial Classification and the major uses applicable to substances included in this rulemaking.

5. Do alternative unpublished exposure guidelines exist, such as those used in private workplaces, which may be suitable for general usage?

Several respondents (see, for example, Exs. 3-741, 3-1095, and 8-47) submitted information about internal corporate guidelines. George M. Talley and Michael Garcia, with the Los Alamos National Laboratory, reported that several industries have such limits (Ex. 3-1095), and the Dow Chemical Company (Ex. 3-741) acknowledged that it has developed internal limits for 250 chemicals used in its plants. However, Dow does not believe that these unpublished exposure guidelines are appropriate "for general usage" because they were developed specifically for Dow's operations and facilities. Dow reports that these limits have not been "appropriately peer reviewed for operations outside our company" (Ex. 3-741, p. 21).

NIOSH commented (Ex. 8-47) that many of the private workplaces it has surveyed have internal exposure guidelines and that, in many cases, these limits are considerably lower than OSHA's existing limits. NIOSH noted that exposure guidelines for two of the substances included in this rulemaking, soluble and insoluble uranium, have been established by the International Commission on Radiation Protection and the National Commission on Radiation Protection.

Several corporations, for example, Rohm and Haas and the Dow Chemical Company, submitted some or all of their internal exposure guidelines to the docket, and OSHA has reviewed these submittals carefully. For the reasons discussed in Section IV.D of this preamble, however, OSHA determined that the ACGIH and NIOSH exposure limits were the most appropriate data bases for OSHA to use as starting points for the rulemaking. In the overwhelming majority of cases, the record has supported this decision, and the limits included in this final rule are consistent with those proposed. In a few instances, OSHA has determined, based on evidence submitted to the record, that another limit is more appropriate; the record evidence in these cases is discussed in detail in the chemical-specific discussions in Section VI.

6. Is there information regarding laboratory analytical procedures which may be used in lieu of those suggested by OSHA to determine exposure to air contaminants?

Several commenters responded to this question (Exs. 3-1095, 8-19, and 8-47). Representatives of the Los Alamos National Laboratory gave OSHA specific information on an improved method for the analysis of methylene dianiline, a substance that is not included in this rulemaking because a Section 6(b) rule is being developed for it at the present time (Ex. 3-1095). NIOSH noted several corrections to the NIOSH Analytical Methods published in Appendix A of the proposal; these corrections have been incorporated into the Appendix, Sampling and Analytical Methods, of this final rule. In addition, NIOSH stated that, in Appendix A of the proposal, several existing NIOSH analytical methods "have been extended to compounds for which the suggested method has not been verified" (Ex. 8-47, p. 22). In several such instances, according to NIOSH, the compound to which the method has been extended differs from the compound for which the method was originally developed.

According to NIOSH, the analytical methods for the following substances would benefit from additional analysis:

  1-3-dichloropropene
  2-hydroxypropyl acrylate
  propargyl alcohol
  isooctyl alcohol
  trichloroacetic acid
  dichloroacetylene
  chlorodifluoromethane
  chloropentafluoroethane
  o-chlorostyrene
  o-chlorotoluene
  cyclopentane
  hexane isomers
  hydrogenated terphenyls
  N-isopropylaniline
  methyl silicate
  nonane
  p-toluidine
  m-toluidine.

Based on its experience, OSHA concludes that there are adequate methods for the sampling and analysis of the substances. As noted in this preamble, additional work is planned regarding further evaluation of these methods. In addition, OSHA's experience shows that the promulgation of new permissible exposure limits has often encouraged the development of appropriate analytical and sampling methods. In 1971, at the time of the adoption of the start-up standards, few sampling and analytical methods had been developed, and NIOSH was charged with the responsibility of developing and validating such methods. The success of this approach is evidenced by the fact that, at the time of the June proposal, only seven substances of the 428 included in the rulemaking were identified as lacking any sampling and analytical methods (53 FR 20978). (In the course of this rulemaking methods for two of these seven, the subtilisins and cyanamide, were submitted to OSHA.) Another example of the incentive to develop methods provided by the setting of new limits can be seen in the case of OSHA's recent ethylene oxide (EtO) standard. At the time of the promulgation of the final rule, in June of 1984, no accurate and easy-to-use method was available to measure short-term EtO exposures; however, by 1986, OSHA's Salt Lake City Laboratory had developed a simple and efficient method using hydrogen-bromine-impregnated charcoal tubes. By 1987, OSHA's research and development effort had led to the development of a commercial product that is now widely available: small, easy-to-use, and inexpensive charcoal tubes for taking employee-breathing-zone measurements of EtO STEL exposures. In addition, several manufacturers have developed passive dosimeters for EtO STEL monitoring. OSHA believes that this same course of research and development, which illustrates the successful working of the market, will occur for the very few substances currently without analytical methods in this rulemaking.

7. Are the proposed exposure limits for each substance appropriate?

OSHA received responses to this question from many rulemaking participants (see, for example, Exs. 3-593, 3-741, 3-891, 3-896, 8-16, 8-19, and 8-47). (In addition, many commenters addressed the appropriateness of the PELs for specific substances; these commenters are addressed in Section VI.C of the preamble.) There was substantial support among these commenters for adoption of the proposed limits that were based on the ACGIH TLVs (Exs. 3-593, 3-891, 3-741, and 3-1095). For example, the Texaco Company stated, "The TLVs are current, well documented, and widely accepted by the industrial hygiene community" (Ex. 3-593). Several respondents felt that the 17 proposed limits that were based on NIOSH Recommended Exposure Limits (RELs) were not appropriate (Ex. 3-593, 3-891, 3-741, and 3-1095). Typical of the reasoning of these commenters was the statement of U.V. Henderson, Jr., Director of Environmental Affairs for the Texaco Corporation:

Only the ACGIH TLVs should be used as the best available source for OSHA to update...[its] exposure standards. The TLVs are current, well documented, and widely accepted by the industrial hygiene community. Many State-approved OSHA programs incorporate the TLVs as their basis for regulation. The NIOSH recommended limits are oftentimes outdated and conservative. Furthermore, feasibility and cost-effectiveness are not always addressed by NIOSH (Ex. 3-593, Attachment, p. 1).

The American Industrial Hygiene Association (AIHA), on the other hand, was entirely in favor of OSHA's use of either an ACGIH or a NIOSH limit, as the case required:

AIHA supports the adoption by OSHA of NIOSH REL values as PELs on a case-by-case basis where such values are supported by the scientific evidence and are feasible from the standpoint of implementation.

NIOSH expressed strong support for this rulemaking in general but submitted specific comments on a number of substances that it believes should have different limits from those proposed (Ex. 8-47). However, NIOSH stated at the hearing that, for substances lacking NIOSH RELs, the use of the ACGIH's TLVs as a starting point is appropriate (Tr. pp. 3-130 - 3-131). NIOSH's substance-specific comments are addressed in connection with the preamble discussion of these substances (see Section VI).

OSHA is gratified by the degree of support for the proposal expressed by these and other rulemaking commenters. The Agency agrees with the AIHA that the appropriate way to establish exposure limits is on a case-by-case basis, considering health effects and feasibility concurrently. This is the methodology used by OSHA in the proposal, and the final rule applies these same principles to the setting of limits for individual substances.

8. Is additional information available for those substances for which ACGIH proposed a higher TLV which might affect OSHA's decision that such a change was not justified?

Only NIOSH (Ex. 8-47) responded specifically to this preamble question. NIOSH expressed the opinion that a comprehensive Section 6(b) rulemaking is required if OSHA is considering raising, rather than lowering, a particular exposure limit. OSHA believes that the issue is not so much the type of rulemaking, i.e., generic vs. substance-specific, as the significance of the risk involved. For example, when raising a limit, the Agency must be able to show that "exposed workers will not be placed at increased risk for the health effects at issue even after the limit in question has been raised or revoked...." (53 FR 21213). The guiding principles were first enunciated by OSHA when the Agency revoked the cotton dust limit for facilities in specific nontextile industries (50 FR 51120 et seq.), and this issue was subsequently discussed in the present rulemaking in the proposal section pertaining to substances for which the ACGIH TLVs are higher than OSHA's existing limits (53 FR 21213). OSHA continues to believe that those principles, rather than the type of rulemaking, constitute the test the Agency must meet when a limit is proposed for raising or revocation.

9. Should implementation dates for some substances be delayed because of sampling/analytical limitations or short term feasibility impact considerations?

Several commenters (Exs. 3-823, 3-891, 3-905, 3-960, 3-1095, 8-16, 3-741, and 3-891) questioned OSHA's promulgation of PELs for substances for which available sampling/analytical methods are not adequate. The Los Alamos National Laboratory (Ex. 3-1095) commented that OSHA "should delay implementation dates for substances that do not have adequate sampling and analytical procedures until such methods are available and validated. It is unreasonable to expect compliance when the chemicals cannot be quantified." NIOSH (Ex. 8-47) commented that some substances have no sampling and analytical methods and that methods for others have not been validated by OSHA or NIOSH.

Appendix A to the proposed rule provided data on the status of sampling and analytical methods for all of the substances included in this rulemaking. For a number of substances, in-house sampling and analysis methods are available; copies of these methods have been supplied by OSHA to any party requesting them, and they are also available in the docket for this rulemaking. No commenter has suggested that any of these in-house methods is inadequate; however, commenters have made general comments on interlaboratory testing and exchange programs and their benefits in terms of method standardization. NIOSH has recommended additional evaluation of the sampling and analytical procedures for several substances.

OSHA has considerable expertise and experience in developing sampling and analytical methods. The Agency has determined that these in-house methods are adequate for enforcement purposes. (Any employer or laboratory wishing a copy of the entire set of methods can purchase them from the ACGIH. Copies of any individual method may be obtained by calling the OSHA Salt Lake City Laboratory, (801) 524-5287.) There have been no objections to any sampling and analytical method for any specific substance. Consequently, OSHA will enforce all of the exposure limits in the final rule except in the seven cases where no sampling and analytical method is known to OSHA.

OSHA identified seven substances in Table I-F-E of the proposal (53 FR 20978) as not having adequate sampling/analysis methods (aluminum alkyls, cyanamide, ethylidene norbornene, hexafluoracetone, mercury [alkyl compounds], subtilisins, and sulfur pentafluoride). (In the course of this rulemaking, methods were found for two of the substances listed in the proposal as having no method: cyanamide and the subtilisins. However, commenters also identified two other substances, phenylphosphine and oxygen difluoride, as lacking methods.) In the final rule, OSHA is promulgating permissible exposure limits for aluminum alkyls, ethylidene norbornene, hexafluoroacetone, mercury [alkyl compounds], oxygen difluoride, phenylphosphine, and sulfur pentafluoride. However, the Agency is staying the enforcement of these limits until an acceptable sampling and analytical technology is devised. When such techniques are developed, OSHA will publish a Federal Register notice indicating that fact and setting forth the date on which enforcement will commence.

10. Is there additional information relative to the OSHA plans to adopt some recommended 10-hour TWA RELs as an 8-hour TWA PEL?

OSHA received few comments in response to this question (see, for example, Exs. 3-1095, 3-623, and 8-47). Representatives of the Los Alamos National Laboratory supported OSHA's use of NIOSH 10-hour limits as 8-hour TWAs:

[W]e support these plans...[because this] is a conservative approach and appropriate (Ex. 3-1095).

George Lathrop of Kerr-McGee Corporation (Ex. 3-623) observed:

[T]he NIOSH Recommended Exposure Levels (REL's) are based upon 10-hour work shifts in a 40-hour work week. The OSHA PEL's, as well as the ACGIH recommended TLV's, are based upon 8-hour work shifts in a 40-hour work week. OSHA preliminarily concludes that the NIOSH REL is equivalent to the OSHA PEL's definition. These two values are equivalent only if their interpretation is based on the length of the work week (i.e., 40 hours). If the interpretation of the OSHA PEL's and the NIOSH REL is based on the length of the work shift (8 or 10 hours, respectively), then these values are not equivalent. If OSHA adopts a NIOSH REL for a particular substance, a notation should exist which identifies the exposure level as based on a 10-hour work shift or the level should be adjusted to represent an 8-hour work shift (Ex. 3-623, p. 3).

NIOSH (Ex. 8-47) provided a detailed response and explained that NIOSH 10-hour RELs are intended to apply to either 8-hour or 10-hour days in a 40-hour workweek. NIOSH explained that the 10-hour REL originated during the energy crisis of the 1970s, when many employers began to use 10-hour/4-day work schedules to conserve energy (Ex. 8-47, p. 25). Thus, the 40-hour workweek rather than the length of a workday is, in NIOSH's view, the important time element in the (concentration) X (time) equation: any given REL can be applied to either four 10-hour days or five 8-hour days without being exceeded. NIOSH supports OSHA's proposal to apply 10-hour NIOSH RELs to 8-hour days by stating:

The action proposed by OSHA in this rulemaking relative to these RELs is consistent with that original intent (Ex. 8-47, p. 26).

In this final rule, OSHA is therefore applying values derived from NIOSH RELs as 8-hour TWA PELs.

11. Does the most current scientific information generally support acceptance of the hypothesis that all C(5)-(8) alkanes are not equally toxic because a metabolite of n-hexane exhibits unique neurotoxic properties?

The C(5)-(8) alkanes include pentane, n-hexane, hexane isomers, n-heptane, octane, and the refined petroleum solvents, namely, rubber solvent (naphtha), Stoddard solvent, and VM & P naphtha. There is some disagreement regarding the question of equal toxicity for all C(5)-(8) alkanes, which impacts on the determination of appropriate PELs on the basis of neuropathic effects resulting from exposure to these substances.

n-Hexane has been shown to produce distal axonopathy in both experimental animals and humans; it is metabolized to 2,5-hexanedione (2,5-HD), which is thought to be the agent that produces peripheral neuropathy after exposure to n-hexane (Schaumburg, Spencer, and Thomas 1983/Ex. 1-228). The ACGIH arrived at a TLV of 50 ppm for n-hexane, based primarily on studies by Miyagaki (1967/Ex. 1-198) and Inoue, Takeuchi, Takeuchi et al. (1970/Ex. 1-75) showing peripheral neuropathies at exposure levels as low as 210 ppm. A number of studies have shown a consistent relationship between exposure levels of 500 to 2000 ppm n-hexane and the development of characteristic peripheral neuropathies (Yamamura 1969/Ex. 1-42; Yamada 1967/Ex. 1-192). Neuropathic effects have also been shown to occur at levels between 210 and 500 ppm n-hexane (Takeuchi, Maluchi, and Takagi 1975/Ex. 1-217).

The NIOSH (1977a/Ex. 1-223) RELs for the C(5)-(8) alkanes are based on the belief that polyneuropathy may be caused by other alkanes (or mixtures of alkanes) and their isomers. NIOSH (1977a/Ex. 1-223) relied heavily on two studies by Gaultier, Rancurel, Piva, and Efthymioc (1973/Ex. 1-123) and Truhaut et al. (1973, as cited in ACGIH 1986, p. 305, "n-Hexane"). The report by Gaultier et al. (1973/Ex. 1-123) reported that five workers in a belt-manufacturing shop developed polyneuropathy as a result of exposure to a solvent that contained 80 percent pentane, 14 percent heptane, and 5 percent hexane. The authors concluded that pentane and heptane, as well as hexane, might also have caused this polyneuritis.

Truhaut et al. (1973, as cited in ACGIH 1986, p. 305, "n-Hexane") exposed Wistar rats to airborne hexane (technical grade) at a concentration of 2000 ppm and to heptane (technical grade) at a concentration of 1500 ppm for five hours/day, five days/week, for one to six months. The analysis of technical grade hexane was: 0.3 percent n-pentane, 25.1 percent 2-methylpentane + cyclopentane, 18.4 percent 3-methylpentane, 45 percent n-hexane, 8 percent methyl cyclopentane, 1.2 percent methyl hexane, and 1.2 percent benzene.

The analysis of technical grade heptane was: 9.8 percent 2-methylhexane, 2,3-dimethyl pentane, and cyclohexane; 16.2 percent 3-methylhexane; 52.4 percent n-heptane; 18.2 percent 2,4-dimethylene, methylcyclohexane, and toluene; 3.3 percent methylheptane; 0.1 percent benzene; and 2.8 percent toluene. The exposed rats developed polyneuropathy, and NIOSH considers this study as evidence indicating that different alkanes cause polyneuropathy.

Since 1977, when NIOSH published its criteria document on alkanes (C(5)-(8)), considerable evidence has accumulated that demonstrates that peripheral neuropathies are caused only by n-hexane and gamma-diketone metabolites (O'Donoghue 1985).

The following summaries of publications show that n-hexane, and not the hexane isomers, n-pentane, n-heptane, or octane, is the primary cause of peripheral neuropathy.

1. Peripheral neuropathy comparable to that seen in human cases has been reproduced using rats, cats, monkeys, hens, and pigeons exposed to n-hexane, practical grade hexanes (which contain n-hexane and benzene), or gasoline containing n-hexane (O'Donoghue 1985).

2. Egan et al. (1980) exposed rats for 22 hours per day, for periods up to six months, at 500-ppm concentrations of an n-hexane "free" isomer mixture; no evidence of neurotoxic effects was observed. A second group of rats exposed to 1 ppm of methyl n-butyl ketone, a positive control, developed histological evidence of peripheral neuropathy after four months of continuous exposure.

3. Takeuchi et al. (1980) performed a comparative study on the neurotoxicity of n-pentane, n-hexane, and n-heptane in the rat. Rats were exposed to 3000 ppm of n-pentane, n-hexane, or n-heptane for 12 hours/day for 16 weeks. The experiment showed that n-hexane disturbed the conduction velocity of the motor nerve and the mixed nerve and prolonged the distal latency in the rats' tails, but that n-pentane and n-heptane did not. Light- and electron-microscopic examinations showed that the peripheral nerve, the neuromuscular junction, and the muscle fibers of the rats exposed to n-hexane or n-heptane showed no particular changes after 16 weeks of exposure. These results show that n-hexane is far more toxic to the peripheral nerve of the rat than is n-pentane or n-heptane.

4. Frontali et al. (1981) exposed rats to n-hexane or n-heptane for 9 to 10 hours/day, 5 to 6 days/week, for a period of 30 weeks. Animals treated with n-hexane at 5000 ppm for 14 weeks or at 2500 ppm for 30 weeks developed the typical giant axonal degeneration already described by Spencer and Schaumburg (1976) in rats treated continuously with 400 to 600 ppm of n-hexane for seven weeks or more. No such alterations were found in the rats subjected to intermittent respiratory treatments with n-pentane at 3000 ppm for 30 weeks or to n-heptane at 1500 ppm for 30 weeks. Again, this demonstrates the greater neurotoxicity of n-hexane compared with that of its isomers.

5. Bahima et al. (1984) conducted a study on female Wistar rats exposed by inhalation to 2000 ppm n-heptane for 12 weeks. No clinical evidence of neurotoxicity was observed after n-heptane exposure. Urinary metabolites were identified by gas chromatography/mass spectrometry. The n-heptane metabolites were 1-, 2-, 3-, and 4-heptanols, 2- and 3-heptanones, 2,5- and 2,6-heptanediols, 5-hydroxy-2-heptanone, 6-hydroxy-2-heptanone, 6-hydroxy-3-heptanone, 2,5- and 2,6-heptanediones, and gamma-valerolactone. 2,5-Heptanedione, a known neurotoxic agent, was the metabolite found in least amounts in the urine. The authors concluded that the lack of neurotoxicity was due to the small amount of 2,5-heptanedione produced after n-heptane exposure.

6. Olson et al. (1986) studied the metabolism of n-octane in Fischer 344 rats. The urinary metabolites of n-octane in rats given n-octane by gavage included 2-octanol, 3-octanol, 5-oxohexanoic acid, and 6-oxoheptanoic acid. n-Octane was not metabolized to a ketone, diketone, or diol derivative. None of the metabolites excreted are known to cause peripheral neuropathy in rats.

7. Spencer and Schaumburg (1985) point out that alkanes normally undergo subterminal carbon oxidation. The likelihood of producing neurotoxic levels of gamma-diketone metabolites from alkanes higher in the series than n-hexane is unlikely. Shorter-chain alkanes (pentane) and hexane isomers free of n-hexane also fail to produce the appropriate metabolite and do not induce neuropathy in experimental animals. The authors further conclude that n-hexane is unique among the alkanes in producing peripheral neuropathy in humans.

8. Recent studies have suggested a mechanism for the structural basis of the neurotoxicity of gamma-diketones. Studies reported by Sayre et al. (1986) and Genter et al. (1987) demonstrate that only those hydrocarbons capable of gamma-diketone and pyrrole formation are potentially neurotoxic. Chronic exposure to gamma-diketones results in the formation of giant neurofilament-containing axonal enlargements.

9. Several commenters (Exs. 3-896, 3-740, and 3-593) were in agreement with the points made in the discussion of this issue, above.

10. NIOSH (1988/Ex. 8-47) continues to support its conclusions as to the neurotoxicity of all of the C(5)-(8) alkanes, as discussed in the 1977 criteria document (1977a/Ex. 1-223). NIOSH believes that n-hexane and other C(5)-(8) alkanes or related chemicals are ultimately metabolized to a gamma-diketone and thus may have similar neurotoxic properties. Accordingly, in the 1977 criteria document on alkanes (C(5) -(8)), NIOSH proposed a REL of 350 mg/m(3) as a TWA concentration for up to a 10-hour work shift for the straight and branched-chain aliphatic isomers of pentane, hexane, heptane, and octane (NIOSH 1977a/Ex. 1-223).

OSHA finds NIOSH's argument on this issue unconvincing in light of the consistent results obtained by a number of investigators using a variety of experimental procedures (see items 1 through 9, above). Therefore, the Agency concludes that only n-hexane has been proved to cause peripheral neuropathy at this time and that other alkanes, such as n-pentane, n-heptane, octane, and the hexane isomers, do not appear to cause peripheral neuropathy. Consequently, OSHA's initial assessment of the relative toxicity of the C(5)-(8) alkanes (53 FR 20998) remains unchanged.

12. OSHA has proposed to use exposure limits from two well-established sets of guidelines as a source of values to update the PELs. Is information available about alternative sources which OSHA might consider for this purpose?

Several commenters (see, for example, Exs. 3-1095, 8-16, and 8-47) responded to this preamble question. Representatives of the Los Alamos National Laboratory (Ex. 3-1095) noted that many industries have voluntary guidelines that might be considered by OSHA if individual companies or trade associations submit them to the docket.

NIOSH (Ex. 8-47) mentioned as excellent sources the 9 data sets referred to by OSHA in the preamble to the proposal (53 FR 20967) and additionally recommended as a potential source the Nordic Expert Group for Documentation of Occupational Exposure Limits. NIOSH stated:

No single source should be expected to stand alone as a comprehensive list of candidates for regulation. OSHA should construct its own comprehensive list by drawing information from all available sources (Ex. 8-47, p. 28).

The Agency used the ACGIH TLVs and NIOSH RELs as starting point and then carefully reviewed the testimony and comments submitted in the course of this rulemaking. If additional information was needed, the Agency examined additional toxicological sources. After careful review and evaluation of this body of information on any given substance and in conformance with Agency policy and statutory requirements, OSHA then determined the appropriate PEL or PELs for each substance.

The American Industrial Hygiene Association (AIHA) also responded to this question (Ex. 8-16). The AIHA submitted a complete set of that organization's Workplace Environmental Exposure Level (WEEL) Guides, with supporting documentation, to OSHA to consider as PEL replacement values. The AIHA described the process by which the WEEL committee establishes these levels and reported that such factors as production rate, acute toxicity, and extent of the interest expressed by the entire AIHA membership are taken into account when deciding what substances to consider for WEELs (Ex. 8-16).

As noted in the preamble to the proposal (53 FR 20967), OSHA considered nine sets of exposure limits, including the WEELs, when the proposal was being developed. OSHA agrees in general that the WEEL values "constitute a well-established set of guidelines for more than 40 substances" (Ex. 8-16); however, the Agency was not able to use the WEELs as replacement PELs in the present rulemaking because, to date, only approximately 40 WEELs have been developed. OSHA concludes that the reasons identified by OSHA in the proposal (53 FR 20967) for using the ACGIH TLVs and the NIOSH RELs as starting points were appropriate.

13. OSHA has outlined its criteria for identifying special situations. Are alternative criteria available which might be used in lieu of these, or in addition to them?

Several rulemaking participants responded to this question; these comments were similar to those provided in response to questions 6 and 9 on analytic methods. See the responses to these questions for a discussion of this issue.

14. OSHA has outlined three alternative procedures for dealing with substances requiring special attention. Are additional approaches available which might be used in lieu of these, or in addition to them?

Four commenters (Exs. 3-1095, 3-593, 3-891, and 8-47) responded to this question, which referred to three approaches suggested by OSHA as possible ways of treating the substances in this rulemaking that require special attention (53 FR 20978-79). These three alternatives were:

(1) in-depth review of all available data for each substance and the establishment of a PEL at the level indicated by this review;

(2) adoption of a limit in this rulemaking, to be followed later by separate rulemaking if the data warrant further analysis; or (3) retain the existing OSHA limits for special-attention substances and proceed later with follow-up review and possible 6(b) rulemaking.

A large majority of commenters endorsed the second approach for substances identified in the course of the rulemaking as warranting special attention (see, for example, Exs. 3-1095, 3-593, 3-891, and 8-47).

The Synthetic Organic Chemicals Manufacturing Association (SOCMA) had no suggestions for alternatives to the three approaches suggested by OSHA (Ex. 3-891). SOCMA found the second approach to dealing with special situations most appropriate; however, the association urged OSHA not to use NIOSH recommended exposure limits (RELs) as interim values but instead to rely on the ACGIH limits for this purpose (Ex. 3-891). The Texaco Company agreed with SOCMA that NIOSH RELs should not be used as interim PELs (Ex. 3-593), while representatives of the Los Alamos National Laboratory (Ex. 3-1095) believe that limits should not be promulgated for those substances lacking sampling and analytical methods. NIOSH (Ex. 8-47) supported OSHA's suggestion that it might be appropriate to mandate limits for all substances immediately and then follow this generic rulemaking with separate rulemaking, as the evidence dictates. NIOSH believes that in some instances, a full 6(b) rulemaking is required. According to NIOSH:

NIOSH concurs with OSHA that it is in the best interest of the worker to promptly provide such increased health protection as is indicated by the evidence in the record (Ex. 8-47, p. 32).

OSHA has concluded that this second approach constitutes the best method of protecting the health and well-being of the largest possible number of workers in the shortest possible time frame. Accordingly, the Agency is today promulgating limits for all but a few of the substances for which limits were proposed. Depending on resources, OSHA may consider for additional rulemaking those substances identified in this preamble as warranting further consideration.

15. OSHA has performed feasibility analyses for the following substances, based on limited available information: acetonitrite, carbon disulfide, carbon monoxide, carbon tetrachloride, chloroform, ethylene dichloride, ethylene glycol dinitrate, fibrous glass dust, hydrogen cyanide, isophorone diisocyanate, nitrogen dioxide, nitroglycerin, and trichloro-ethylene. Is further information available which might be used to supplement the present findings regarding the feasibility of achieving these levels in the workplace?

The Synthetic Organic Chemicals Manufacturing Association (SOCMA) (Ex. 3-891), the Dow Chemical Company (Ex. 3-741), the Teepak Corporation (Ex. 8-19), and NIOSH (Ex. 8-47) each responded to this question. The Dow Chemical Company (Ex. 3-741) commented on the difficulty of obtaining feasibility information, especially for "the small business entities which will be most heavily impacted," while SOCMA (Ex. 3-891) opposed the promulgation of NIOSH limits if the feasibility information available was not adequate. NIOSH (Ex. 8-47) submitted feasibility information to OSHA for the substances listed and for acetone, chlorine, styrene, and sulfur dioxide as well. OSHA appreciates NIOSH's submission and is using this information in its feasibility analyses for individual substances (see Section VI).

For the final rule, OSHA went beyond the feasibility analyses presented in the proposal. The Agency incorporated the substantial amount of feasibility data submitted by NIOSH and other submitters. OSHA also reviewed the site visit reports submitted into the record. Based on the entire record, OSHA has concluded that the Agency has sufficient feasibility data to support the final rule's PELs. These data are analyzed in depth, by industry sector, in Section VII.

16. OSHA has made a preliminary assessment of the proposed rulemaking's impact on large and small establishments. The Act requires OSHA to determine whether a regulation will have a significant impact on a substantial number of small entities, pursuant to the Regulatory Flexibility Act of 1980, 5 U.S.C. 601 et seq. Is there additional information regarding implementation of this rule for small businesses and entities which OSHA should consider?

The U.S. Borax and Chemical Corporation (Ex. 3-744), SOCMA (Ex. 3-891), and the Dow Chemical Company (Ex. 3-741) each responded to this preamble question. SOCMA expects "some adverse impact" on its smaller member companies because these companies are likely to have greater difficulty than others in absorbing the costs of controls (Ex. 3-891). SOCMA believes that such companies are particularly likely to be severely impacted if REL, rather than TLV, values are promulgated as OSHA PELs; in SOCMA's views, selection of TLV values as PELs "will substantially reduce the feasibility problems of the proposal" (Ex. 3-891). The Dow Chemical Company (Ex. 3-741) agrees with SOCMA that the largest impact of the rulemaking will be on smaller establishments, and also that promulgation of values consistent with those of the ACGIH, rather than with those of NIOSH, will mitigate any such impact.

Eugene Smith, Vice President for Government and Public Affairs of the U.S. Borax and Chemical Corporation, believes that the uses of "sodium tetraborate as well as boron oxide are so ubiquitous in their applications that a complete documentation of their uses in industrial and household applications is virtually impossible" (Ex. 3-744, p. 5). Mr. Smith reports that he is aware of "very small companies who would find installation of the type of engineering controls" described in the proposal financially difficult to implement (Ex. 3-744, p. 5). OSHA is sympathetic to the concerns of U.S. Borax and has focused much of the economic and feasibility analysis for this rule on small entities that will be affected by this revision or expansion of permissible exposure limits. The Regulatory Flexibility Analysis (RFA) accompanying this final rule fully considers the impacts of this regulation on these entities and describes the magnitude of any differential small-business impacts. In the RFA, OSHA concludes that the final rule is feasible for small businesses.

17. OSHA has proposed PELs for some substances, where the basis for this proposal also includes a carcinogenicity designation (e.g., TLV with an A1 or A2 designation; REL with a Ca designation). Should OSHA include a similar carcinogen designation in the Z-4 table in this rulemaking?

Several commenters (Exs. 3-741, 3-1008, 3-1095, 3-593, 3-660, 3-891, 8-16, and 8-47) responded to this question. Some commenters (Exs. 3-741 and 3-891) indicated that OSHA's Hazard Communication Standard already requires employers to inform employees about the carcinogenic hazards of any substances listed as carcinogens by IARC or NTP. According to these respondents, identification of substances as carcinogens in the Z tables would therefore be duplicative and could cause confusion (Ex. 3-891). In addition, adding such information to a table could be confusing because there is no method of adding extensive explanatory material to a table. Other commenters (Exs. 3-593, 3-1095, 8-16 and 8-47) favored the addition of a cancer designation to carcinogenic substances included in the Z tables. For example, the American Industrial Hygiene Association (AIHA) stated:

AIHA would support the inclusion of a designation on carcinogenicity ... provided that such designation reflects the weight of evidence for carcinogenic effects .... (Ex. 8-16, p. 14).

NIOSH (Ex. 8-47) concurred in recommending the inclusion of such a designation in the final rule's Z tables.

OSHA has carefully reviewed the record evidence on this issue and has investigated the various evaluative criteria used by scientific and regulatory bodies to determine the classification of a substance as a carcinogen. The Agency notes that each organization has a different system and that the criteria used rarely coincide. Thus, the ACGIH uses two designations, A1 and A2, to reflect the strength of the evidence for a substance's carcinogenicity, while the EPA has five classifications that represent different kinds of evidence. OSHA believes that the inclusion of a cancer designation on the Z tables would further complicate this already complex situation by adding yet another classification system to those already in use. OSHA is also concerned that adding a cancer designation to the Z-table limits would require frequent updating and revision as additional substances are identified as carcinogens in the future. Therefore, OSHA has determined that the present system (in which the Z tables present the exposure limits for a substance, while the Hazard Communication Standard (29 CFR 1910.1200) determines whether the evidence for a particular substance is such as to require employers to describe its carcinogenicity in their hazard communication programs) is the clearest and simplest approach to alerting workers to the hazards present in their workplaces.

18. OSHA has preliminarily decided that for substances where the ACGIH, TLV is a TWA and the NIOSH, REL is a Ceiling Value which is the same or one-half of the TWA, OSHA will propose that the TWA be adopted as the PEL. Should this approach be modified in the final rulemaking? What approach should be used when the converse of this situation (TLV, Ceiling-REL, TWA) exists?

Several commenters were cautious concerning this approach. Los Alamos (Ex. 3-1095) and NIOSH (Ex. 8-47) concurred, recognizing that an analysis of the data supporting a proposed limit must be developed on a case-by-case basis to discern which limit is appropriate. NIOSH (Ex. 8-47) also stated that the simple numerical relationship that OSHA has proposed is not a scientifically sound basis for choosing between a TWA and a ceiling value.

The Synthetic Organic Chemical Manufacturers Association (SOCMA) (Ex. 3-891) recommended that the TLV be adopted, whether the TLV is a ceiling value or a TWA, since TLVs are the most appropriate levels for adoption. The American Federation of State and County Municipal Employees (AFSCME) (Ex. 3-1043) recommended:

OSHA should adopt most protective limit unless source dictates otherwise. Ceiling and STELs provide greater protection than TWA of the same numerical value (Ex. 3-1043, p. 5).

Other commenters (Exs. 3-1043, 3-42, and 3-1095) also wanted to ensure that OSHA understood the difference between TWA and ceiling values. OSHA understands that TWAs are not equal to ceiling limits and concurs with the definition of these two limits discussed in NIOSH's submission:

A TWA is appropriate as a limit when the toxic effect of the substance is directly related to the total dose received in a daily exposure. Ceiling values are intended to minimize toxic effects related to the peak exposure. Ceiling values are necessary when there are immediate acute responses to an air contaminant independent of the total daily dose or when chronic effects are dose-rate responses. Ceiling values are also used to minimize the total daily dose when there is intermittent occupational exposure, e.g., ethylene oxide (Ex. 8-47).

OSHA has always recognized the differences between TWA and ceiling limits; in the proposal, OSHA adopted the TWAs only as a starting point. Since that time, OSHA has analyzed the various docket submissions regarding individual substances. Based on these individual analyses, OSHA has developed updated PELs on a case-by-case basis. (For information regarding a specific substance, refer to the discussion for that individual substance.)

19. OSHA preliminarily plans to adopt a phased start-up schedule. This would include an initial start-up requirement permitting the use of alternate control methods for revised PELs, followed at a later date by the required use of control methods fully consistent with the methods of compliance priorities in effect at that time. OSHA will shortly be requesting comments on the hierarchy of controls. An alternate approach is to set compliance dates for engineering controls based on final determinations of that rulemaking. OSHA solicits comments on those approaches and suggestions regarding the appropriate times for the two proposed start-up dates.

The proposed rule (53 FR 20960 et seq.) suggested six months from the publication date of the final regulation as a reasonable time for employers to evaluate the exposures of their employees and to come into compliance using any combination of respirators, work practices, and engineering controls. Many commenters, such as the Texaco Company (Ex. 3-593) and the Synthetic Organic Chemical Manufacturers Association (SOCMA) (Ex. 3-891), indicated that the 6-month compliance date phase-in was appropriate. The Kerr-McGee Corporation (Ex. 3-623) was more specific in its comments and contended that the initial six-month period should be extended to a 24-month period to allow industry sufficient time to monitor and develop the necessary control measures. The American Paper Institute (Ex. 3-685) was also of the opinion that an initial six-month compliance period would be too short.

OSHA has extended the period to come into compliance using any method from six months from the date of publication to approximately six months from the effective date; this action adds two months to this period. OSHA concludes, based on the Agency's experience and many comments, that a six-month period after the effective date is sufficient to evaluate exposures and commence a respirator program. Most employers will only have employee overexposures to a relatively few substances. (See also the discussion under the Scope and Application of the standard.) Several companies stated that OSHA should grant a specific extension for their particular industries as a consequence of feasibility concerns. OSHA has, however, considered the issues of feasibility raised by rulemaking participants for specific industries and has determined that it is feasible, with few exceptions, for employers in affected industries to achieve compliance with the limits promulgated in the final rule using engineering controls generally. These exceptions are discussed in Section VII of this preamble.

In the proposal, OSHA also estimated that all employers, including those who would have to control exposures to several different chemicals, could achieve compliance within four years using the hierarchy of controls (i.e., preference for engineering controls and work practices, and, if not feasible, personal protective equipment) specified in 29 CFR 1910.1000(e). Regarding the four-year engineering implementation date schedule, OSHA received a number of comments. Most trade associations and employers supported the four-year period, and most unions suggested that one to two years would be sufficient. The State of Washington used 60 days for a similar regulation and reports that there were few difficulties with compliance. NIOSH (Ex. 8-47) suggested that two years was a reasonable time for compliance. The longest period suggested was the period recommended by the Fibre Box Association (Ex. 3-823), which stated that 10 years for compliance by industry was a reasonable time frame. OSHA has evaluated the data from various industries regarding the feasibility of compliance and has determined that it is feasible for employers in nearly all operations to achieve compliance, using engineering and work practice controls, by December 31, 1992. In light of the scope of this regulation, OSHA concludes that a shorter period would not be appropriate.

Since OSHA is in the process of reviewing the hierarchy of controls, OSHA requested comment on whether the compliance period should be tied into the completion of that rulemaking. There were few responses to this query. A few companies (see, for example, Exs. 3-669 and 3-527) suggested that the Agency delay the four-year coming-into-compliance period until after publication of any new regulations on this subject; these commenters cited costs of compliance as a major concern. The Dow Chemical Co. (Ex. 3-741) urged the Agency not to wait to set a start-up date for this rule. OSHA concludes that the December 31, 1992 deadline specified is appropriate and is supported by most of industry. Section 1910.1000(e) has been in effect for 18 years and reflects the view of most industrial hygienists. (See the Summary and Explanation section of the preamble, Section VIII B, for further details.)

20. OSHA requests comment on whether the establishment of margins of safety below lowest observed or no-effect levels is consistent with the concept of "significant risk," and on whether the specific margins of safety proposed for specific chemicals are appropriate.

Several commenters (see, for example, Exs. 3-744, 3-1095, 3-660, 8-16, and 8-47) submitted information to OSHA in response to this question. Representatives of the Los Alamos National Laboratory (Ex. 3-1095) noted that safety factors must be established on a case-by-case basis, while the U.S. Borax and Chemical Corporation (Ex. 3-744) commented that dose-response information is needed before safety factors can be applied to set an exposure limit. The American Industrial Hygiene Association (AIHA) (Ex. 8-16) is of the opinion that OSHA should adopt a "uniform toxicologic basis for assigning such factors" and should change the term "safety factor" to "uncertainty factor" in the final rule.

NIOSH (Ex. 8-47) stated that safety factors cannot be used to estimate human risk and are therefore not related to the magnitude or significance of a risk; instead, safety factors are intended to reflect uncertainty in knowledge or available data. NIOSH endorsed the use of safety factors as a "pragmatic method" to develop standards except when a nonthreshold process, such as the induction of cancer, is the outcome of concern (Ex. 8-47). NIOSH believes that "standards based on a margin of safety...as well as standards derived from a case-by-case evaluation, [should] be periodically reviewed to determine what new information is available" (Ex. 8-47).

OSHA is pleased that these commenters believe that the use of safety factors or margins of safety is an appropriate method of adjusting for the absence of complete information in the standards-setting process. OSHA agrees with NIOSH that this approach to limit-setting is appropriate when threshold effects are the endpoints of concern. (For a full discussion of safety factors, see Section VI.A and the Legal Analysis section of this preamble.)

21. OSHA has identified sensory irritation, which causes rhinitis, cough, sputum production, chest pain, wheezing and dyspnea, as material impairment of health. OSHA invites comments on this understanding.

Many commenters (see, for example, Exs. 3-744, 3-1095, 3-896, 8-47, 3-660, 3-593 and 3-665) responded to this preamble question. A few were of the opinion that transitory or acute effects should not be considered material impairment of health; the U.S. Borax and Chemical Corporation (Ex. 3-744) believes that transitory "rhinitis, cough, sputum production, chest pain, wheezing, and dyspnea" do not constitute material health impairment. Stanley Dryden of Chevron Corporation believes that "mild irritants and odorants" should not be considered to pose a risk of material health impairment (Ex. 3-896).

Most commenters, however, agreed with OSHA that the signs and symptoms listed in this question should be regarded as material health impairments (Exs. 8-47, 3-1095, 3-660 and 3-593). NIOSH stated:

The recognition of sensory irritation as potentially being "material impairment of health" is consistent with the current scientific consensus related to health effects of environmental agents.

Mucous membrane irritants can cause increased blink frequency and tearing; nasal discharge, congestion, and sneezing; and cough, sputum production, chest discomfort, wheezing, chest tightness, and dyspnea. Work environments often require levels of physical and mental performance considerably greater than encountered in daily living. Even in the absence of any permanent impairment, the symptoms listed can interfere with job performance and safety.

Mucous membrane irritation can result in inflammation, which may lead to increased susceptibility to nonspecific irritants and infectious agents. For example, experimental ozone exposure in humans results in increased airway reactivity. Also, studies of exposure to environmental tobacco smoke have shown irritative symptoms and evidence of increased frequency of respiratory tract illnesses in young children and decreased pulmonary function in adults....

Mucous membrane irritation is associated with respiratory illnesses, depending on the composition of specific exposure and on the dose, duration, and frequency of exposure. No universally applicable conclusion can be drawn at this time regarding the association between irritative symptoms and permanent injury or dysfunction. Where certain individuals show no measurable impairment after an exposure, even when experiencing irritative symptoms, others may develop identifiable dysfunction.

Aside from the effects of irritation, mucous membrane exposure may result in absorption of a substance, with resultant systemic toxicity. An inflamed mucous membrane may be an even more effective route of absorption, either for the irritant or for other substances. Furthermore, injury to broncho-pulmonary membranes can impair removal of particulates from the respiratory system (Ex. 8-47).

Thus, according to NIOSH, sensory irritants interfere with job performance and safety, cause inflammation, may increase the victim's susceptibility to other irritants and infectious agents, lead to permanent injury or dysfunction, or permit greater absorption of hazardous substances (Ex. 8-47). In sum, NIOSH and most other respondents agree with OSHA that sensory irritation caused by occupational exposure to the irritant substances included in this final rule constitutes a material impairment of health (see Section VI.C.3).

22. The question also arises of whether odorants present material impairment of health. That issue also might arise in the context of other substances. Based on the evidence in the final record concerning this issue, OSHA will determine if the criteria detailed in Section IV-C-16 have been met, and take appropriate action. OSHA requests comment on this issue.

Section IV.C.11 of the preamble to the proposed rule (53 FR 21135-21136) described the adverse effects associated with exposure to four substances included in the category of odorants. These substances are: isopropyl ether, phenyl ether, propylene glycol monomethyl ether, and vinyl toluene. NIOSH (Ex. 8-47), the National Renderers Association (Ex. 3-11), the E.I. do Pont Company (Ex. 3-660), the Pharmaceutical Manufacturers Association (Ex. 3-1161), and the Los Alamos National Laboratory (Ex. 3-1095), among others, commented on this issue. According to representatives of the Los Alamos National Laboratory, odorants should not be considered as causing a material health impairment (Ex. 3-1095); John Beary, III, a physician speaking for the Pharmaceutical Manufacturers Association, is of the same opinion (Ex. 3-1161).

NIOSH described several important reasons for minimizing objectionable odors in the workplace:

Odors emitted by industrial chemicals often play an important role in occupational safety and health. When odors can be detected before health effects occur, they may provide early warning of exposure. A number of chemicals have strong odors at concentrations which are otherwise minimally toxic. These odors may cause undue health concerns among exposed workers or may create safety hazards by distracting workers from their tasks. Strong odors in the workplace may also mask the presence of other, more toxic substances. Strong odors can produce irritation and/or nausea at high concentrations, although these effects may be reversible following cessation of exposure. Olfactory fatigue often occurs and should be considered a functional impairment that can result in increased worker exposure. Olfactory fatigue can reduce the wearer's ability to sense inadequate respirator performance of air-purifying respirators (Ex. 8-47, p. 41).

NIOSH thus concurs with OSHA's view noted in the preamble to the proposal that intolerable odors may have serious adverse effects in the workplace. And, although it is true that there is wide variation in individual responses to odor (i.e., in the ability to detect an odor), it is also true that one individual may respond to an odor with only mild discomfort, while another becomes overtly nauseated.

OSHA has carefully weighed all of the evidence in the record on the toxicological significance of exposures to odorant chemicals. The Agency finds that odor effects alone do not constitute material health impairment. (See the further discussion at p. 2365 and pp. 2602-04.) However, OSHA notes that it is exceedingly rare for a substance only to cause odor effects. It is generally the case that odorant chemicals also cause toxic effects, such as sensory irritation or incipient central nervous system effects that manifest as headaches, nausea, vertigo, or diplopia. However, for the purposes of this rulemaking, OSHA concludes that odor alone does not constitute material health impairment.

23. Is there exposure information available which can be supplied which will refine OSHA's estimates of employee exposures and overexposures to the substances being regulated?

Although two other commenters (Exs. 3-744, 3-742) mentioned this proposal question, the only substantive comment received by OSHA in response specifically to this question came from NIOSH (Ex. 8-47), which noted that it was submitting to the docket all relevant Health Hazard Evaluations (HHEs). OSHA has reviewed these HHEs as they apply to the substances and sectors of interest and has used data from these documents in the Regulatory Impact Analysis that accompanies this final rule.

24. Is there information available which can be supplied to improve or supplement the engineering controls identified as necessary in order to reduce exposure levels? Is there additional cost data which can be supplied to refine the annual costs associated with these controls?

In response to this preamble question, the U.S. Borax and Chemical Corporation (Ex. 3-744) submitted data to show that, for the years 1979 through 1987, the average per-year cost for environmental control units at its Borax Operation was $37,609. According to this commenter, since a large plant would have many such units, the cost per plant for SIC 28 facilities presented by OSHA in the proposal (53 FR 21376) is "orders of magnitude" lower than the costs plants would actually experience. In response to U.S. Borax, OSHA points out that the costs presented in the proposal were average annual compliance costs for all large plants across all of SIC 28. Thus, it is likely that OSHA's costs may not exactly approximate those of any particular plant but will, in the aggregate, reflect those of the average plant in this sector. OSHA has received no cost data or information that calls these average compliance cost estimates into question.

In general, feasibility and cost data were directed toward individual substances rather than being submitted in response to this question. These data are discussed in detail in Section VII.

25. Under what conditions, involving which industrial processes, will respirators be needed during the start-up period, for maintenance operations, or where other controls are infeasible in order to protect employees at the proposed exposure levels? Are respirators currently being used under the conditions identified, or would they need to be purchased? Please describe the type of respirator currently in use or needed.

This question elicited responses from several commenters (Exs. 3-593, 3-741, 3-891, 3-1095 and 8-47). The Texaco Corporation (Ex. 3-593) identified several operations where respirators are required; these included field maintenance of process equipment in refinery and petrochemical plants, confined space operations, asbestos stripping, and equipment repair. The Synthetic Organic Chemical Manufacturing Association (SOCMA) (Ex. 3-891) noted that respirator use varies from job to job and that engineering controls are not always feasible. The Dow Chemical Company (Ex. 3-741) reported that respirators are currently being used in industry where infrequent tasks make the costs of engineering controls infeasible; examples of such operations are maintenance operations, emergency operations, and certain infrequently performed process operations. Dow had no information on the type or extent of current respirator use. NIOSH (Ex. 8-47) submitted data from a 1982 NIOSH-sponsored contractor report that shows that, in 1980, 19.1 percent of mining, manufacturing, and construction workers wore or had access to certified respirators. The same report showed that the market shares of self-contained breathing apparatus, single-use, and chemical cartridge respirators were approximately equal and ranged from 25 to 30 percent each (Ex. 8-47).

OSHA did not raise the issue of methods of compliance in this rulemaking. This question was asked to gather factual information. Section VII discusses those few areas identified where respirator use may be needed. (See also the Legal Analysis sector.)

26. As a result of simultaneously regulating many substances, what cost savings will be realized in purchasing and installing engineering controls? Are alternate engineering controls available to achieve the lower permissible exposure limits being proposed?

OSHA received no substantive responses to this question. Several participants, including NIOSH and the unions presented evidence on situations in which lower levels than those proposed could be achieved by means of engineering and work practice controls. These cases are discussed in Section VII of the preamble.

27. What is the current state of technology control and financing in firms which would need to comply with reduced exposure limits to wood dust?

No commenters provided substantive responses to this question. Much information was submitted on the issues alluded to in this question; however, this information was not submitted in response to this question but rather in relation to the technological and economic feasibility of achieving the proposed limits for wood dust. This information is discussed in Section VII.

In addition to these 27 specific questions, OSHA solicited comments on the appropriateness of considering 10-, 15-, and 20-minute NIOSH RELs as 15-minute STELs and on the appropriateness of adopting PELs having other durations (i.e., 30-, 60-, or 120-minute "ceilings" ), such as those recommended by NIOSH (53 FR 21242).

Only the Kerr-McGee Corporation specifically addressed this question. Kerr-McGee (Ex. 3-623) was concerned that OSHA might, in the final rule, establish the NIOSH 30-, 60-, or 120-minute ceilings as 15-minute STELs. OSHA agrees with Kerr-McGee that this approach would not be appropriate at this time without additional analysis. Where the NIOSH limit for a substance was for a duration of 30, 60, or 120 minutes, OSHA has generally maintained these intervals in the final rule. The final rule adopts 15-minute STELs in cases where NIOSH has recommended a 10-, 15-, or 20-minute limit.

[54 FR 2332, Jan. 19, 1989; 54 FR 14909, April 13, 1989; 54 FR 28154, July 5, 1989]



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