The Role of the US Occupational Safety and Health Administration

Abstract The Occupational Safety and Health Act, passed by the US Congress in 1970, establishes the authority and basic principles by which health standards are promulgated by the Occupational Safety and Health Administration. These principles have been interpreted and refined by 25 years of case law that has developed as a direct result of rule-making activity. The Act requires OSHA to develop health standards that “ensure 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 … for the period of his working life.” Thus, OSHA has a fundamental responsibility under the Act to establish health standards that are based on health evidence and that are designed to minimize risk to each individual who may be exposed to a particular hazard for a working lifetime. The Act and accompanying case law also explicitly require OSHA to consider the technological and economic feasibility in developing new standards. In practice, when promulgating new standards dealing with potential carcinogens, the stringency of the standard is more constrained by feasibility considerations than by the weight of health evidence or magnitude of risk. In one of the more significant legal rulings relevant to standards development, the US Supreme Court has ruled that OSHA, before issuing a new standard, must demonstrate that a significant risk of harm exists among workers exposed to the hazard in question, and that the new standard will substantially reduce that risk. For carcinogenic hazards, this necessitates conducting quantitative risk assessments to meet this legal test. Although OSHA has not defined any risk level as representing a de minimis risk, the Agency has determined as a policy matter that lifetime risks of a magnitude of 1 cancer case per 1,000 workers constitute a significant risk that warrant further reducing exposures, provided that such reduction is both technologically and economically feasible. OSHA evaluates both human epidemiological and experimental animal data in determining the potential carcinogenicity of workplace contaminants, and often relies on scientific organizations such as IARC for evaluating the overall weight of evidence. Quantitative risk assessments are conducted both in-house and by outside experts. During the public comment periods and hearings conducted for each rule-making, OSHA also receives quantitative risk assessments conducted by interested parties, and must evaluate those assessments in reaching regulatory decisions. Because each new standard must be developed under this formal public process, OSHA's risk analysis is subjected to a high degree of scientific scrutiny. Specific to the subject of inorganic carcinogens, OSHA has promulgated comprehensive standards covering three hazardous materials (inorganic arsenic, asbestos, and cadmium), and is developing a proposal to issue a new standard on another substance (hexavalent chromium). Comprehensive health standards include requirements to: comply with permissible exposure limits; conduct exposure monitoring, medical surveillance, and employee training; and develop programs for using respirators and other protective equipment. The permissible exposure limit for a new standard is developed directly from quantitative risk assessment results and feasibility considerations. Epidemiologic studies have provided the data that the Agency has relied upon for quantitative risk assessment for these standards; however, in the cadmium rule-making, animal data also played an important role in evaluating the relative potency of various cadmium compounds. It has been OSHA's experience in conducting risk assessments for both inorganic and organic compounds that risk estimates based on animal data are consistent with, and often lower than, estimates based on epidemiological studies, that is, use of animal data in risk assessment has not been shown in OSHA's experience to systematically overestimate risks to workers. OSHA has been collecting and reviewing scientific information on two other materials, silica and man-made mineral fibres, as part of an ongoing prioritization process to identify future candidates for either rule-making or information dissemination activities.