Expanding the scope of environmental risk assessment to better include differential vulnerability and susceptibility.

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.