Risk Assessment: The Path of Uncertainty
Sheridan, Peter J., Occupational Hazards
Risk Assessment: The Path Of Uncertainty
Expert observations on the strengths and limitations of risk assessment.
Risk assessment slipped quietly into the lexicon of some occupational safety and health pros back in the 1970s when OSHA arrived on the scene. But the phrase remained relatively obscure until 1980 when the U.S. Supreme Court handed down its benzene decision, mandating OSHA to establish significant risk in promulgating a health standard.
From that time on, risk assessment, as a means of determining significant risk, was at once prominent and perennially controversial. Take, for example, OSHA's current effort to revise its cadmium standard.
The OSHA PELs for cadmium are 100 micrograms per cubic meter of air for cadmium fumes and 200 micrograms per cubic meter of air for cadmium dust.
OSHA is proposing two alternative, 8-hour time-weighted average (TWA) permissible exposure limits (PELs) for all cadmium compounds -- 5 micrograms of cadmium per cubic meter of air (5 ug/[m.sup.3]) or one microgram of cadmium per cubic meter of air (1 ug/[m.sup.3]). The proposed standard also includes alternative, 15-minute excursion limits (ELs) of five times the TWA PEL (25 ug/[m.sup.3] or 5 ug/[m.sup.3]) and alternative action levels of 2.5 ug/[m.sup.3] or 0.5 ug/[m.sup.3] respectively.
OSHA is proposing alternative TWA PELs because extensive respirator usage is required in some industries at the lower permissible exposure limit and because of the uncertainties inherent in quantitative risk assessments, according to agency spokesmen.
OSHA estimates that reducing cadmium exposures in every workplace to 5 ug/[m.sup.3] would prevent four cancer deaths and 11 to 41 cases of kidney dysfunction annually. The agency estimates that the 1 ug/[m.sup.3] TWA PEL would prevent 14 cancer deaths and 13 to 189 kidney dysfunction cases annually. OSHA estimated the costs for a 5 ug/[m.sup.3] standard at around $57 million a year and the costs for a 1 ug/[m.sup.3] standard at about $160 million a year.
As frequently happens in OSHA standards-setting, industry is challenging the agency's risk assessment. The Shipbuilders Council and the Cadmium Council regard the safe level of exposure arrived at by OSHA as too low.
Gathering the Data
Before entering the risk assessment arena as an active participant, OSHA gathers available research data from many quarters. Whatever the substance, the inquiry is similar: OSHA looks for laboratory and field observations of adverse effects; exposure to particular agents; extrapolation from animal testing; and field measurements.
If the information gathered indicates the need, the agency conducts a risk assessment within the framework developed by the National Academy of Sciences, consisting of hazard identification, dose-response evaluation, exposure assessment, and risk characterization. OSHA health scientists, under Director of Health Standards Charles Adkins, track the literature on the substance, conduct searches and surveys, and seek to compile a good exposure file. After an exhaustive review of the data, the decision is made by Adkins whether to move ahead into standards development.
Even in the frequently combative world of safety and health regulation, risk assessments are widely regarded as having the merit of synthesizing available scientific data upon which regulatory and policy decisions can be predicated. But what about the weaknesses of risk assessments?
"There's never enough good scientific data," acknowledged Hugh Conway, director of OSHA's Office of Regulatory Analysis. "More epidemiological treatment is needed. More animal testing is needed, and so it goes -- right down the line."
OSHA's Conway said that the bottom line that principals frequently differ over is, "What's the safe level of exposure?" As we indicated, that's where the battle between the industry groups and OSHA standard-setters is being waged on the proposed cadmium standard. …