The Four-Step Framework
The EPA's human health risk assessment framework consists of four steps. Hazard Identification determines which chemicals at a site could cause health effects, reviewing toxicological and epidemiological studies. Dose-Response Assessment establishes the quantitative relationship between dose and adverse effects, deriving cancer slope factors (risk per mg/kg/day) for carcinogens and Reference Doses (RfD) for non-carcinogens. Exposure Assessment estimates how much of each chemical people actually contact—through which pathways, how often, and for how long. Risk Characterization integrates the previous three steps to calculate numerical risk estimates, describing both the magnitude and uncertainty of risks. This framework has been applied to thousands of Superfund sites and provides a transparent, reproducible methodology for environmental decision-making.