Provisional guidance for quantitative risk assessment of polycyclic aromatic hydrocarbons. Final report

PAHs are products of incomplete combustion of organic materials; sources are, thus, widespread including cigarette smoke, municipal waste incineration, wood stove emissions, coal conversion, energy production form fossil fuels, and automobile and diesel exhaust. As PAHs are common environmental contaminants, it is important that EPA have a scientifically justified, consistent approach to the evaluation of human health risk from exposure to these compounds. For the majority of PAHs classified as B2, probable human carcinogen, data are insufficient for calculation of an inhalation or drinking water unit risk. Benzo(a)pyrene (BAP) is the most completely studied of the PAHs, and data, while problematic, are sufficient for calculation of quantitative estimates of carcinogenic potency. Toxicity Equivalency Factors (TEF) have been used by U.S. EPA on an interim basis for risk assessment of chlorinated dibenzodioxins and dibenzofurans. Data for PAHs do not meet all criteria for use of TEF. The document presents a somewhat different approach to quantitative estimation for PAHs using weighted potential potencies.