Regulations (Preambles to Final Rules) - Table of Contents|
| Record Type:||Occupational Exposure to Asbestos, Tremolite, Anthophyllite and Actinolite|
| Title:||Section 6 - VI. Other Regulatory Issues|
VI. Other Regulatory Issues
a. Regulatory Options
In the proposal OSHA discussed a number of regulatory options to the proposed removal of non-asbestiform ATA from the asbestos standards. Because of OSHA conclusions regarding the health effects evidence, certain of these options are not supported by this rulemaking record.
(1) The first option discussed in the proposal is to continue to regulate ATA in the 1986 asbestos standards. The Agency has determined that on this record, there is a lack of substantial evidence to conclude that non-asbestiform ATA presents a risk of asbestos-related disease to exposed workers of similar incidence or magnitude to the risk created by asbestos. Therefore the evidence does not support regulating non-asbestiform ATA exposure in the same manner as asbestos exposure.
The health data are too uncertain to provide a basis for estimating potential risk from non-asbestiform ATA. This evidence is not sufficient to perform a reasonable independent risk assessment for ATA. Therefore, continuing regulation in the same standard, at a different PEL is not a viable option. OSHA concludes that the evidence and analyses available at this time do not show sufficient similarities between non-asbestiform ATA and asbestos to regulate them together.
(2) Another option was to continue to regulate non-asbestiform ATA under the 1972 asbestos standard. However, the conclusion that the record evidence is insufficient to show that non-asbestiform ATA presents a health risk similar in type and magnitude to asbestos and thus should not be regulated under the 1986 asbestos standards, substantially weakens a major rationale for regulating OSHA under the 1972 asbestos standard as well. The 1972 standard was based on the health effects of asbestos and not the non-asbestiform minerals.
Virtually all of the health data submitted and examined in this rulemaking was not available in 1972. Therefore, the determination of health effects for non-asbestiform ATA based on the record of this proceeding is based on more evidence and superior analyses than in any earlier asbestos rulemaking.
Also, OSHA's regulatory decisions are required by law to be based on "the best available evidence".(OSH Act, Section 6(b)(5)). Although OSHA is not necessarily required to reopen regulatory determinations when new evidence is presented, once a rulemaking proceeding is held, and new, previously unavailable evidence is submitted to that record on important issues OSHA may consider the issue in light of such new evidence. The agency notes that it stated its intention to make a new determination on the current record concerning the health effects of non-asbestiform ATA.
In addition, OSHA finds that removing non-asbestiform ATA from the scope of the 1972 asbestos standard will not pose a significant risk to employees exposed to those minerals. OSHA incorporates here, its previous discussion in the health effects section, which sets forth the Agency's view of the evidence relating to the non-malignant disease potential of ATA. The evidence available implicates talc containing ATA as a causative agent of nonmalignant respiratory disease; however, exposure to ATA alone is insufficiently linked to the production of such disease.
As noted above employees exposed to talc containing ATA will be protected under the Air Contaminants Standard (29 CFR 1910.1001). OSHA believes that the application of the talc limit in the Air Contaminants Standard, for that portion of their exposure which is related to talc, or the standard's mixture formula, will protect exposed employees against a significant risk of nonmalignant disease.
Also, removing the protection of the 1972 asbestos standard from workers exposed to non-asbestiform ATA will not leave them with a significant risk of developing malignant disease. OSHA has found that the available evidence is insufficient to conclude that exposure to non-asbestiform ATA is linked to the development of cancer. The suggestion that long thin fibers of non-asbestiform ATA, which exceed the dimensions for counting asbestos fibers, may have carcinogenic potential was not disproven by the evidence in this proceeding, however, neither was it supported by substantial evidence. Also, even if long, thin non-asbestiform ATA fibers have some carcinogenic potential, the record shows that it is not likely that workers may be exposed to a significant risk from such fibers if the 2 f/cc limit of the 1972 standard is lifted.
First, evidence in the record indicates that, long, thin particles of non-asbestiform ATA occur infrequently. For example, in the industries using tremolitic talc, which are the industries with the highest potential exposure to ATA, there is little evidence that exposures to long, thin particles of non-asbestiform ATA have ever exceeded the 1972 asbestos limit of 2 f/cc. Nor is there evidence that non-asbestiform ATA particles, appearing as a contaminant of any other industrial product (e.g. crushed stone products), attain enhanced dimensions which, if measured, would exceed the 2 f/cc limit of the 1972 standard. Second, there are no dose-response data which can be used to derive a quantitative risk estimate for non-asbestiform ATA as a carcinogen, so OSHA's risk estimate for ATA would be based on qualitative information. The approach formerly considered most promising, basing ATA risk on asbestos risk, has been rejected by the Agency, as explained at length in this document. The Agency believes that no other qualitative approach to assessing non-asbestiform ATA carcinogenic risk is supported by the evidence.
Third, for the industries with the highest potential ATA exposure, which includes those which purchase tremolitic talc as a constituent of products such as ceramic tile and paint, the talc limit, and the mixture formula in the Air Contaminants Standard will apply. OSHA believes that these limits will protect employees against any possible excesses of any malignant disease as well as non-malignant disease.
Therefore, OSHA finds that removing non-asbestiform ATA from the 1972 standard meets the requirements set out by the Supreme Court for agency deregulation in Motor Vehicles Manufacturers Association v.State Farm Mutual Automobile Insurance Co. (State Farm), 463 U.S. 29, 1983, and is consistent with Agency interpretations of that decision.
(3) The third option discussed in the proposal is to exclude non-asbestiform ATA from the scope of the revised asbestos standards and to initiate a separate 6(b) rulemaking for either industrial talc (tremolitic talc) or non-asbestiform ATA minerals which attain certain dimensions, such as a 3:1 aspect ratio and are longer than 5 um. As stated above, the results of OSHA's examination of the health effects evidence in this proceeding do not provide sufficient data to permit the Agency to estimate the risk, if any, to exposed employees from continued exposure at the 1972 asbestos standard's PEL of 2 f/cc, or at current exposure levels in covered places of employment. There was agreement among participants who addressed the issue that exposure to tremolitic talc at historic levels is associated with excess nonmalignant respiratory disease (see e.g. Dr. Boehlecke, testifying for R.T. Vanderbilt, at Tr. 5/10, pp. 100-101). OSHA's contractor estimated current exposure levels in industries using such talc containing products, even without local exhaust ventilation, as far less then such historic levels.(See CONSAD report, Ex. 465) No additional data concerning exposure levels of such workers was submitted to the rulemaking record. With no basis to estimate risk to exposed employees from talc containing non-asbestiform ATA, OSHA is unable to formulate a proposed standard to protect such workers at this time. As stated above, OSHA believes that the application of the appropriate exposure limits in the Air Contaminants Standard to exposures to constituents of tremolitic talc, and to ATA, will protect employees against significant risks of disease.
If further information is submitted to OSHA in the future, which shows that workers in industries using talc containing non-asbestiform ATA, or other non-asbestiform ATA using industries, are at present risk of developing exposure related disease, OSHA may reconsider this regulatory decision.
(4) The fourth option is to regulate non-asbestiform ATA under a specific listing in the air contaminants standard, including consideration of a listing for non-asbestiform ATA. OSHA has chosen this approach but non-asbestiform ATA will be covered by listing for particulates not otherwise regulated (PNOR) in Table Z-1-A of 1910.1000 [15 mg/m (total dust); 5 mg/m (respirable dust)], which is designed to protect against the significant risk of respiratory effects which all particulates create at higher levels of exposure.
OSHA is not regulating ATA under the listing for talc. OSHA notes that the health evidence concerning the nonmalignant disease potential of talc containing tremolite is not specific to any one component of the product, and there is evidence suggesting that talc, not containing non-asbestiform ATA, also may cause respiratory disease (See for example the preamble to the Air Contaminants Standard, 54 FR at 2526). Accordingly, OSHA revised the PEL for talc to 2 mg/m(3) on January 19, 1989 (54 FR 2332 to 2983, CFR 1910.1000). As talc causes respiratory disease and non-asbestiform ATA as a particulate causes respiratory effects, OSHA concludes that when workers are exposed to mixtures of such dusts with different PELs, the mixture formula applies. Where exposure is to talc containing non-asbestiform ATA, if the employer wishes to avoid separately identifying each component to apply the mixture formula, the entire product may be considered as the substance with the lower PEL.
b. Fiber definition issues
During this rulemaking the NSA and other participants requested that OSHA validate for industry a feasible method of distinguishing asbestos fibers from non-asbestiform particles or other mineral particles which meet the dimensional cutoffs in the asbestos standards. Further, OSHA is asked to define "asbestos" in terms of such differential counting strategy. NSA agrees with the Agency that when the environment is one in which "known asbestos is likely to be the only airborne particle of regulatory concern, it (3:1 aspect ratio criterion) can be an acceptable and economical basis for monitoring worker exposure to substances that pose health risks."(479-1G, p. 22). However, in the crushed stone industry, other particles, NSA insists, will be counted even though they are not asbestos, or even non-asbestiform minerals simply because they have attained aspect ratios of 3:1. OSHA does not believe these scenarios are realistic. The asbestos standards have been in effect since 1972; yet industry presented no data, evidence or testimony that showed the impact of the 3:1 aspect ratio on the crushed stone industry. Producers should know if their products contain asbestos fibers, by surveying deposits, examining hand samples, and doing bulk sampling.
The issue of whether individual fibers of ATA can be identified as to mineral type was further addressed by other witnesses. Dr. Arthur Langer, testifying on his own behalf, noted that "...in some instances single, isolated particles may be impossible to distinguish, i.e. acicular cleavage fragment from asbestiform fibril". (Ex. 517, Tab 5) Dr. Spooner pointed out that identification of an airborne fiber is hindered, when as happens in an industrial hygiene setting "we don't have the opportunity to know where the material is coming from, nor do we have the opportunity to look at a very large population of fibers..." (Tr. 5/8, p. 117-118) NIOSH testified that it was "unaware of any routine analytical methods that can be used to differentiate between airborne exposures to asbestos fibers and non-asbestiform cleavage fragments that meet the microscopic definition of a fiber." (Tr. 5/9, p. 13).
The OSHA reference method may be insufficient in mixed fiber environments to distinguish asbestos from other particles in all cases. However, OSHA believes that currently, producers and users of mineral products feasibly identify asbestos and distinguish it from other mineral fibers or particles. Dr. Langer noted "I would use polarized light microscopy to characterize materials used the work place or characterize mine environments. Someone has to go to some mine or quarry or operation or plant or factory to see whether or not asbestos materials are present, and there are standard techniques to analyze materials and find out whether or not asbestos is present. You could use phase contrast microscopy once you establish what you're dealing with." (Tr. 5/11 at 226). Dr. Langer recommended that OSHA define "asbestos" as certain minerals which display certain properties, which apply to "large aggregates". Such properties are for example, polyfilamentous bundles, made up of unit fibrils, displaying anomalous optical properties, etc. (Id at 227). Dr. Addison commented that for "at the last eight years we've been training a regular number of people in polarized light microscope techniques, ... to recognize the characteristic properties on the macroscopic scale and on the microscopic scale, to come up with what we consider to be a fully authoritative identification of the material as asbestos. It's really not a difficult task." (Ibid).
Dr. Langer also noted that in his knowledge the former Manville Corporation routinely used polarized light microscopy in many of their plants to analyze air samples, where manmade vitreous fiber was mixed with asbestos fiber"(Tr. 5/11, p. 225).
OSHA also notes that differential counting of fibers has been performed by its laboratory and other laboratories in the past. According to the Agency's chief microscopist, identification of individual fibers is assisted by knowledge of the source of the contaminant, the industrial context, and the skill of the microscopist.(Ex. 410-23).
However, Dr. R.J. Lee, testifying on behalf of the NSA, presented a new analytical method for use in mixed mineral environments. (Ex. 490F) This method was presented as a differential counting procedure for assessing the asbestiform particle population in dusts that include both asbestiform and non-asbestiform particles. Dr. Lee's proposed method uses the current NIOSH 7400 PCM method but in addition incorporates steps to account for particles with widths less than 1 micrometer and particles which are bundles in order to differentiate between those particles which are fibers and those particles which are cleavage fragments.
During the hearing Dr. Lee was questioned as to the validity of this method and whether or not it would alter asbestos counts. In response to this questioning Dr. Lee conducted and submitted the results of a round robin analysis of his proposed method (Ex. 534). In the round robin analysis 6 different labs performed comparisons of particle counts on a variety of different dust samples using the current NIOSH 7400 PCM method and Dr. Lee's proposed method. Although somewhat limited, the results of the round robin analysis indicate that there is little variability between the asbestos fiber counts using the NIOSH method and the asbestos fiber counts using Lee's proposed method. However, according to Dr. Lee, the proposed method allows one to differentiate between asbestos fibers and non-asbestiform cleavage fragments more readily than current differential counting procedures.
Despite the fact that the proposed method appears to provide a feasible means of discriminating between asbestiform fibers and non-asbestiform cleavage fragments, OSHA is reluctant to change its current approved methodology based on such limited data (i.e. one round robin analysis), especially since the Agency notes that changes to the asbestos standards affect a much wider regulated community than participants in this rulemaking. OSHA believes that the adoption of any method would require more extensive testing using a broader range of samples more closely associated with the typical types of occupational exposures covered by the OSHA standards. In addition, considerable expenditures of time and money could be required to insure that labs are adequately training technicians and proficiently using the new method. Before such costs are imposed OSHA believes it would be prudent to better examine the validity of a new method. The Agency notes that the high hazard presented by asbestos exposure requires that any regulatory change affecting counting asbestos fibers err on the side of worker protection. OSHA believes that the burden on employers in affected industries to show that particles are not asbestos is not unreasonable, given the risk presented by undercounting of asbestos, and the claims that asbestos contamination of non-asbestiform products is not common. For these reasons, as well as the fact that OSHA has acknowledged and allowed the use of differential counting with the current method, the Agency does not believe it is either appropriate or necessary at this time to change its current analytical method. The Agency intends to include in its compliance policy governing mixed fiber settings, provision for the introduction of appropriate evidence concerning fiber width, and other relevant evidence to show that particles counted by PCM are not asbestos fibers .
As discussed in the NPRM, rather than change the analytical procedure, Dr. Ann Wylie proposed changing the aspect ratio from 3:1 to 10:1 as a means of discriminating between asbestos fibers and non-asbestiform cleavage fragments (See 55 FR 4951-52). Dr. Wylie reiterated her proposal in the hearings and presented evidence to show that when populations of particles are viewed with respect to the distribution of their aspect ratios, one can easily distinguish between populations of asbestos fibers and populations of cleavage fragments (Tr. 5/9, pp. 102-107). Dr. Wylie stated that for particles which are greater than 5 um in length, the majority of non-asbestiform particles have aspect ratios less than 10:1 and the majority of asbestos particles (i.e. fibers) have aspect ratios greater than 10:1. Thus she concluded that changing the aspect ratio from 3:1 to 10:1 provides a means of excluding non-asbestiform particles from particles counts while maintaining the same asbestos particle counts one would have obtained using a 3:1 aspect ratio. However as noted above in this discussion, Dr. Spooner points out that Dr. Wylie's observations, as do her definitions of asbestos, apply to populations of particles and the analyst is often not looking at a population of particles when viewing air exposure monitoring samples (Tr. 5/8, pp. 117-118). Moreover as was noted in the proposal, OSHA is reluctant to change its current method based on the findings of one report. OSHA reaffirms its earlier finding and is not, in this rule, changing its dimensional criteria for aspect ratio in its definition of asbestos.
- [57 FR 24310, June 8, 1992]
|Regulations (Preambles to Final Rules) - Table of Contents|