A Graphical Display of Risk Information

Abstract

Cancer risk assessment and management of hazardous air pollutants under the Vinyl Chloride decision requires a two-step process. When regulating a pollutant such as benzene, EPA must first determine whether a proposed level of emissions is “safe” and then in a second step whether it provides an ample margin of safety. Safety is judged in terms of both maximum individual risk and population risk (“cancer incidence”). Both determining safety and setting an ample margin require consideration of uncertainties in risk assessment. This paper proposes a graphical display of maximum individual risk versus population risk, with degree of certainty represented by the size of circles showing various possible estimates of risks. Risk criteria are represented by a criterion band based on risk management precedents. Visual inspection of the diagram can aid in standard setting.