November 27, 2013

Occupational Exposure to Respirable Crystalline Silica

  • Michael L. Marlow

    Professor of Economics at California Polytechnic State University, San Luis Obispo
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Occupational Safety and Health Administration (OSHA) states that over 60 epidemiological studies (covering more than 30 occupational groups) clearly indicate that respirable crystalline silica1 (hereafter cited in text as silica) is a human lung carcinogen. OSHA also cites studies that indicate that occupational exposure to silica causes other adverse respiratory effects, such as fatal nonmalignant silicosis and chronic obstructive pulmonary disease, and an elevated risk of end-stage renal disease. 

OSHA estimates the excess lifetime risk2 to workers exposed over a working life of 45 years at the current general industry permissible exposure limit3 (PEL) is between 13 and 60 deaths per 1,000 workers. For exposure over a working life at existing construction and shipyard employment PELs (estimated to range between 250 and 500 μg/m3), estimated excess risk lies between 37 and 653 deaths per 1,000 workers. Reducing these PELs to the proposed PEL of 50 μg/m3 silica results in a substantial reduction of these risks, to a range estimated to be between 6 and 26 deaths per 1,000 workers. OSHA concludes that the evidence on the public health risk associated with exposure at current permissible PELs is of significant magnitude. 

OSHA is proposing a PEL of 50 μg/m3 based on the argument that it will substantially reduce risks to an estimated range between 6 and 26 deaths from lung cancer per 1,000 workers. The current PEL is 100 μg/ m3 for general industry and maritime and 250 μg/m3 for construction. The proposal would thus cut in half the amount of silica exposure allowed for general industry and maritime workers and reduce by 80 percent the exposure allowed for those in the construction industry. OSHA estimates that the proposed rule will save nearly 700 lives and prevent 1,600 new cases of silicosis per year once the full effects of the rule are realized. OSHA is also proposing an action level of 25 μg/m3 that triggers initial and periodic exposure monitoring only once the action level is reached or exceeded.4 OSHA believes that many employers will be willing to lower silica exposure to equal to or below that 25 μg/m3 action level in order to avoid exposure monitoring. 

Overall, OSHA has failed to make a sufficiently strong case for the regulation. 

OSHA’s analysis contains numerous flaws, inconsistencies, and sloppy arguments. An especially poorly conceived argument surrounds a claim that an “action level” of 25 μg/m3 creates significant incentive for employers to maintain workplaces that meet this level (one-half the proposed PEL of 50 μg/m3) and thus will make workplaces even safer. But OSHA’s own analysis determined that a PEL of 25 μg/m3 would not be feasible (that is, engineering and work practices would not be sufficient to reduce silica exposures to a PEL of 25 μg/m3 or below) in most operations most of the time. OSHA even admits that it did not attempt to identify engineering controls or their costs to meet a PEL of 25 μg/m3 for this very reason. Surprisingly, OSHA still maintains many employers would have sufficient incentives to meet silica exposures of 25 μg/ m3 despite OSHA’s own conclusion of infeasibility. 

OSHA’s argument that there is a market failure, in the form of imperfect information about the hazards of silica exposure, is also flawed. While OSHA has made a reasonable general theoretical case for regulation, it fails to develop what an optimal regulation might look like. OSHA does not provide adequate justification for the proposed regulation, in view of lack of compliance with existing regulations and expected benefits. OSHA largely ignores the problems of enforcement of the proposed standards. Many businesses are already out of compliance with the current, less stringent regulation that has been in place for roughly 40 years. OSHA’s analysis assumes full compliance, which overstates health improvement to the degree to which proposed regulations will not be fully enforced, just as current regulations are inadequately enforced. Costs are also greatly underestimated since OSHA assumes that all firms are currently in compliance with the existing standard, so the only costs are those moving from the existing standard to the proposed one. The agency’s reliance on vague rationales of correcting inequities is also very troubling. Finally, OSHA places too little weight on what might be the most cost effective solution to silica exposure: increased use of personal protective equipment. OSHA needs to consider a wider set of alternatives within a model of an optimal level of worker safety that realistically takes compliance into account and that can be quantitatively assessed through conventional benefit-cost analysis. 

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