Compliance Versus Risk in Assessing Occupational Exposures. Rogelio Tornero-Velez, Elaine Symanski, Hans Kromhout, Rong. C. Yu, and Stephen M. Rappaport, School of Public Health, University of North Carolina, Chapel Hill, NC 27599-7400
We apply a random-effects model to data from 179 groups of workers, exposed to a variety of chemical agents, and obtain parameter estimates for the group mean exposure and the within- and between-worker components of variance. These estimates are then combined with occupational exposure limits (OELs) to generate estimates of exceedance [g, the likelihood that any measurement would exceed an OEL] and overexposure [q, the likelihood that an individual worker’s long-term mean exposure exceeds the OEL]. We regard q as a relevant measure of individual risk for chemicals, such as carcinogens, which produce chronic effects after long-term exposures but not necessarily for acutely-toxic substances which can produce effects relatively quickly. We show that the practice of compliance testing can significantly underestimate the health risk when sample sizes are small. We demonstrate further that, because the relationship between q and g depends upon the within- and between-worker components of variance, it cannot be assumed a priori that exceedance is a conservative surrogate for overexposure. Thus, we conclude that assessment practices which focus upon either compliance or exceedance are problematic and recommend that employers evaluate exposures relative to the probabilities of overexposure.