Quantitative Approaches in Use to Assess Cancer Risk

Scientists have long used conventional toxicological methods to establish “safe levels of exposure” for chemicals presumed to have threshold health effects or doses below which significant effects are unlikely to occur. These same methods cannot be used to establish safe levels of exposure for non‐threshold pollutants, such as carcinogens. Therefore, Federal regulatory agencies in the United States are using risk assessment methods to provide information for public health policy decisions concerning increases in risk associated with increases in exposure to carcinogenic and other non‐threshold pollutants. Acceptable exposure/risk levels are decided by policymakers who consider descriptions and estimates of risks together with social and economic benefits from the uses of the chemical. This paper focuses on the development of quantitative risk assessment approaches by Federal regulatory agencies in the United States, and identifies the mathematical models currently being used for risk extrapolation, including their inherent uncertainties. The uncertainties and limitations of these methods have led some scientists to question the utility of quantitative risk extrapolation. The experience of the U.S. Environmental Protection Agency (EPA), as summarized in this paper, can provide a realistic basis for evaluating the pros and cons. Finally, shortcomings in current risk assessment methods and their use in policy decisions are explored, and areas for possible improvement, given current scientific knowledge, are identified.