Calculation of human health risk-based screening levels (RBSLs) for petroleum.

Hazardous waste site managers and regulators can decide easily whether site contamination requires remediation to protect human health, but defining the extent of cleanup is often an enormous challenge. When is the site clean enough for human access and use? Risk assessment tools can be used to help answer this question. One can calculate chemical-specific risk-based screening levels (RBSLs) in environmental media (e.g. soil, water, and food) that correspond to "acceptable" levels of risk. RBSLs can be calculated for individual chemicals and chemical mixtures, specific to various exposure pathways. In calculating RBSLs, one must account for the fact that people may be exposed to more than one chemical by more than one exposure pathway. Fate and transport models may be needed to predict how people might become exposed to site contamination in the future. Examples RBSLs for non-cancer effects are calculated to illustrate the utility and limitations of RBSLs for making risk-based decisions at petroleum release sites.