摘要：The central paradigm of the Environmental Protection Agency is risk assessment. We examined how differential responses across population groups could be better integrated into the environmental risk assessment process, providing tools to achieve greater equity in health status in addition to risk reduction. Such integration was difficult with paradigms like reference dose and was easier with consideration of dose–response curves, which incorporated nontrivial effects observed at low doses for common exposures. We identified 6 assumptions implicit in standard chemical risk assessments that should changed: (1) risk independence, (2) risk averaging, (3) risk nontransferability, (4) risk synchrony, (5) risk accumulation and chaining, and (6) quantification of numbers of persons above certain thresholds or limit values sufficient to characterize risk. THE CENTRAL PARADIGM FOR the US Environmental Protection Agency (EPA) standard setting is risk assessment. Based on scientific data, the EPA prepares quantitative estimates of changes in health status that will result in different potential levels of a standard, and uses that quantification as input into decision-making for situations in which risk management depends on other data as well. Specific regulatory actions are targeted to particular environmental agents, whose marginal impacts, sources, and control strategies often differ. A cruder approach is often taken. An acceptable dose of a chemical is defined (e.g., reference dose [RfD]), and risk assessment merely quantifies the number of people above versus below this dose or number for different regulatory choices. Implicit in the latter approach is that this quantity is meaningful and that risk is zero below the RfD and the same above the RfD, irrespective of the extent to which actual exposure exceeds the RfD. These simplifying assumptions can lead to both inaccuracy in risk estimation and inattention to distributional aspects. A recent US National Academy of Sciences report declared that “..risk assessment is at a crossroads.” 1 (p.ix) Its key recommendation was to abandon the RfD approach whenever possible and move to a quantitative estimate of changes in health. We support the National Academy of Science's conclusions, arguing that only with actual quantification of risk can differential patterns of susceptibility be examined, and point out that this makes understanding the shape of the dose–response relation central to risk assessment. In this article, the conceptual issues are addressed, and in 2 related articles, 2 , 3 examples are provided of where these concepts are important. Methodology is also discussed.
