II. Pertinent Legal Authority

The primary purpose of the Occupational Safety and Health Act (29 U.S.C. 651 et seq.) (The Act) is to assure, so far as possible safe and healthful working conditions for every American worker over the period of his or her working lifetime. One means prescribed by the Congress to achieve this goal is the mandate given to and the concomitant authority vested in, the Secretary of Labor to set mandatory safety and health standards. The Congress specifically mandated that:

The Secretary, in promulgating standards dealing with toxic materials or harmful physical agents under this subsection, shall set the standards which most adequately assures, to the extent feasible, on the basis of the best available evidence, that no employee will suffer material impairment of health or functional capacity even if such employee has regular exposure to the hazard dealt with by such standard for the period of his working life. Development of standards under this section shall be based upon research, demonstrations, experiments, and such other information as may be appropriate. In addition to the attainment of the highest degree of health and safety protection for the employee, other considerations shall be the latest available scientific data in the field, the feasibility of standards, and experience gained under this and other health and safety laws. [Section 6(b)(5)].

Where appropriate, OSHA standards are required to include provisions for labels or other appropriate forms of warning to apprise employees of hazards, suitable protective equipment, exposure control procedures, monitoring and measuring of employee exposure, employee access to the results of monitoring, appropriate medical examinations or other tests. These must be available at no cost to the employee [Section 6(b)(7)]. Standards may also prescribe recordkeeping requirements where necessary or appropriate for the enforcement of the Act or for developing information regarding occupational accidents and illnesses [Section 8(c)].

Section 3(8) of the Act, 29 U.S.C. 652(8), defines an occupational safety and health standard as follows:

A standard which requires condition, or the adoption or use of one or more practices, means, methods, operations or processes, reasonably necessary or appropriate to provide a safe or healthful employment and place of employment.

The Supreme Court has said that section 3(8) must be applied to the issuance of a permanent standard to determine that it is reasonably necessary and appropriate to remedy a significant risk of material health impairment (Industrial Union Department v. American Petroleum Institute, 448 U.S. 607 (1980)). This "significant risk" determination constitutes a finding that, in the absence of the changes in practices mandated by the standard, the workplaces would be "unsafe" in the sense that workers would be threatened with a significant risk of harm. (Id. at 642).

The court indicated, however, that the significant risk determination is not a "mathematical straitjacket," and that "OSHA is not required to support its finding that significant risk exists with anything approaching certainty." The Court ruled that "a reviewing Court [is] to give OSHA some leeway where its findings must be made on the frontiers of scientific knowledge [and that ] * * * the Agency is free to use conservative assumptions in interpreting the data with respect to carcinogens, risking error on the side of over protection rather than under protection" (448 U.S. at 655).

The Court also stated that "while the Agency must support its finding that a certain level of risk exists with substantial evidence, we recognize that its determination that a particular level of risk is `significant' will be based largely on policy considerations." (488 U.S. at 655, n.62). It is in the Agency's burden to make this showing, based on substantial evidence that it is at least more likely than not that such a substantial risk exists.

After OSHA has determined that significant risk exists and that such risk can be reduced or eliminated by the proposed standard, it must set the standard "which most adequately assures, to the extent feasible on the basis of the best available evidence, that no employees will suffer material impairment of health" (section 6(b)(5) of the Act). The Supreme Court has interpreted this section to mean that when adopted an OSHA standard must be the most protective possible to eliminate significant impairment of health, subject to the constraints of technological and economic feasibility (American Textile Manufacturers Institute, Inc. v. Donovan, 452 U.S. 490 (1981)).

In addition, section 4(b)(2) of the Act provides that OSHA's general industry standards would apply to construction and other workplaces where the Assistant Secretary has determined those standards are more effective than the standard which would otherwise apply.

In this document, OSHA is amending the revised standards for Asbestos (29 CFR parts 1910.1001 and 1926.58) to remove non-asbestiform ATA from their scope. The basis for this decision is the Agency's determination that the available evidence is insufficient to conclude that non-asbestiform ATA present the same type or magnitude of health effect as asbestos.

The inclusion of the non-asbestiform minerals under the 1972 standard was based on the Agency's view that non-asbestiform ATA likely subjected exposed employees to a significant risk of asbestos related disease and in the same way as asbestos. Additional evidence and evaluations which have been submitted to OSHA led to a reassessment of OSHA's views.

The Supreme Court in Motor Vehicle Manufacturers Association v. State Farm Mutual Automobile Insurance Co. (State Farm), (463 U.S. 29, 1983) held that " an Agency changing its course by rescinding a rule is obligated to supply a reasoned analysis for the change beyond that which may be required when an agency does not act in the first instance * * * " 463 U.S. at 42. OSHA has previously stated the approach it will follow in raising or eliminating exposure limits in two places. Those are in its reconsideration for the exposure to cotton dust in the non-textile sector at 50 FR 51132-3, October 12, 1985 and in its Air Contaminants Final Rule (54 FR 2698), January 19, 1989.

The evidence must indicate that significant risk is unlikely to exist as a result of the change in the regulation. OSHA's final action in this rulemaking is based on the direction of the Supreme Court in State Farm and is consistent with OSHA's previous approach.

Also, the Supreme Court in its State Farm decision held that recision of a rule is arbitrary if, inter alia the Agency does not consider an important aspect of the problem (463 U.S. at 43). The Court held that an essential component of reasoned decision making requires discussing why alternative ways of achieving the objectives of the Act cannot be adopted. OSHA believes that here it must consider such regulatory alternatives presented by its review of the record, or which are suggested by participants who show the significant benefit and feasibility of such recommendations.

Significance of risk for non-asbestiform-ATA

OSHA is empowered to regulate exposure to toxic substances where substantial evidence shows the existence of a significant risk of material impairment. For asbestos, OSHA has found that a lifetime excess cancer risk of 6.7 per thousand and a lifetime asbestosis risk of 5 cases per thousand are correlated with asbestos exposure at the 1986 time - weighted average PEL of 0.2 f/cc and that a still significant risk exists at that level.

OSHA's 1986 risk assessment for asbestos, which was upheld by the United States Court of Appeals for the District of Columbia Circuit, was based on the results of a large number of epidemiologic studies which evaluated human cohorts which were undisputedly exposed to asbestos. For lung cancer, OSHA looked at eight studies which contained good data for the calculation of the dose - response relationship for lung cancer, and six studies to calculate the dose - response relationship for mesothelioma. OSHA's evaluation of these studies indicated that the potency coefficients of lung cancer appeared lower where airborne fibers are relatively coarse, than in certain manufacturing operations where the fibers are fine (See 51 FR at 22623).

OSHA did not use the results of any study involving worker exposure to non-asbestiform ATA in its asbestos risk assessment. In determining to include ATA in its 1986 asbestos standards the Agency reasoned that the chemical and structural similarities in varieties of the same minerals allowed a presumption of similar risk, so long as OSHA's fiber definition corresponded to dimensions likely to be carcinogenic. Confirming evidence of similar risk consisted of epidemiologic studies of tremolitic talc miners which showed excess lung cancer and other asbestos related disease. However, at the time, OSHA acknowledged that the studies, although showing positive results, were inconclusive in that the studies did not prove a causal relationship between the mineral exposure and cancer.(51 FR 22631).

Thus, the primary basis for including the non-asbestiform varieties of ATA in OSHA's asbestos standards was the Agency's belief that fiber populations with similar "index" fiber counts, presented essentially the same risk, regardless of whether those "index" fibers were strictly asbestos in the mineralogical sense. Dimensions of the "index" fiber in the asbestos standards was a length of at least 5 micrometers with a 3:1 or greater aspect ratio. OSHA believed that the primary determinant of biological activity of asbestos is fiber dimension, and that varieties of asbestos minerals of relevant dimension have the same carcinogenic and fibrogenic potential per fiber.(See 51 FR at 22638).

This determination was the practical equivalent of a qualitative risk assessment for ATA. Given the chemical and structural similarities between non-asbestiform and asbestiform ATA, OSHA determined that similar regulation of both varieties was warranted, so long as dimensionally appropriate fibers were counted.

This decision squarely fit OSHA's mainstream authority to regulate less known substances based on extrapolation from evidence of known related carcinogens. OSHA believed that the Agency was not required to demonstrate the toxicity of each chemical it seeks to regulate through studies demonstrating a clear line of causation. (See Environmental Defense Fund v. E.P.A., 598 F.2d 62(C.A.D.C. 1978). OSHA's decision to regulate like asbestos the closely related non-asbestiform varieties of three asbestos minerals was not the first time that OSHA or other regulatory agencies had regulated closely related substances based primarily on evidence relating to the more known variant. In its arsenic standard OSHA had treated pentavalent arsenic as presenting the same health risk as trivalent arsenic, which was conclusively carcinogenic. OSHA based its decision on evidence consisting of studies which demonstrated positive mutagenic and genetic effects by both trivalent and pentavalent varieties and two positive epidemiologic studies of pentavalent arsenic. A negative study of pentavalent arsenic was rejected by OSHA for problematic exposure description and small numbers of workers studied. OSHA determined that substantial evidence existed to consider both forms of arsenic carcinogenic, and regulated them under the same standard. (43 FR 19584) This was upheld in ASARCO v. OSHA, 746 F2d. 483, (4th Circuit, 1984).

Similarly, EPA has regulated less chlorinated PCBs as carcinogens based on extrapolations from data concerning more chlorinated PCBs, which undisputedly showed carcinogenicity. Confirming evidence consisted of some positive in vivo and in vitro tests for the less chlorinated variety. (EDF v. EPA, supra).

Thus, OSHA and other agencies have based risk assessments for one substance on the quantitative data relating to a related substance if substantial data in the record support the equivalency of risk in a qualitative way, even though dose - response data allowing a separate risk assessment are not available. For example, in the PCB case, positive in vivo and in vitro studies showed excess risk of about the same magnitude. In the arsenic case, positive epidemiologic and animal data of the less studied substance, corresponded to risk estimates for the more studied variant. Further in both cases, the biological relationship was based on the same factors as the assumed toxic mechanisms.

In this rulemaking, OSHA has reopened the issue of whether non-asbestiform ATA should be regulated like asbestos based on its similarity to the known carcinogen. The evidence submitted to this record includes, in the Agency's view, virtually all relevant data and comment existing on this issue, much of which was not previously considered by the Agency. OSHA has examined this record to evaluate whether the risk of the non-asbestiform varieties of ATA can be derived by analogy to asbestos. After a review of this greatly enhanced record, OSHA has reversed its decision of 1986, and determined that there is insufficient evidence to regulate non-asbestiform ATA primarily by extrapolation from data relating to asbestos. Reliable confirming evidence is lacking; animal experimental evidence either shows no or greatly reduced effect for non-asbestiform ATA, epidemiologic evidence relating to non-asbestiform ATA is inconclusive and/or flawed, and dimensional hypotheses of carcinogenicity appear to offer only partial explanations, and in any event are too imprecise for regulatory use. Thus, the record does not contain substantial evidence to support a determination that non-asbestiform ATA presents a health risk similar to asbestos, based primarily on extrapolation from evidence relating to asbestos.

As further discussed in the Health Effects section, below, OSHA has also determined that substantial evidence is lacking in this record to support the regulation of non-asbestiform ATA in the asbestos standards or in a separate health standard based on a separate risk assessment which shows that these mineral forms present the same kind and extent of risk as asbestos, or a lesser but still significant risk to exposed employees greater than the risk caused by particulates not otherwise regulated.

[57 FR 24310, June 8, 1992]