98 EPA Risk Characterization Risk f(toxicity,exposure) 9 Threshold Risk Assessment MOE NOAEL(mg/kg BW day) Exposure(mg/kg BW day) ·Non-threshold(cancer）Risk Assessment Risk (probability)=q*X exposure OSU q=cancer slope factor,usually expressed in units of proportion (of a population)affected per unit exposure(e.g.mg/kg/day) regonEPA Risk Characterization • Threshold Risk Assessment • Non-threshold (cancer) Risk Assessment MOE = Exposure (mg/kg BW day) NOAEL (mg/kg BW day) Risk (probability) = q1 Risk (probability) = q1 * X exposure * X exposure Risk = f (toxicity, exposure) q1 *= cancer slope factor, usually expressed in units of proportion (of a population) affected per unit exposure (e.g. mg/kg/day)