Risk assessment: the default conservatism controversy

EPA cancer risk assessment rests heavily on defaults. Defaults are a reduction of science to generic principles selected as a policy matter on the basis of "conservatism" for use in risk assessment. Conservatism is understood to mean a choice to avoid underestimating risk. The recent report of the National Academy of Sciences (1994) has turned the spotlight on the controversy regarding the use of generic principles as defaults and whether conservatism is the appropriate value criterion for their selection. Defaults had their origin in the early 1970s and the debate has continued regarding the scientific basis for the defaults and whether a conservatism, a value that the NAS said is "beyond science," is appropriate as a basis for the policy choices. This paper briefly examines the CAPRA recommendations to reduce the reliance on defaults, the history of the default conservatism controversy, and EPA's initial draft response to the CAPRA recommendations.