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DEVELOPMENT OF RELATIVE POTENCY ESTIMATES FOR PAHS AND HYDROCARBON COMBUSTION PRODUCT FRACTIONS COMPARED TO BENZO[A]PYRENE AND THEIR USE IN CARCINOGENIC RISK ASSESSMENTS
Citation:
Thorslund, T. AND D. Farrar. DEVELOPMENT OF RELATIVE POTENCY ESTIMATES FOR PAHS AND HYDROCARBON COMBUSTION PRODUCT FRACTIONS COMPARED TO BENZO[A]PYRENE AND THEIR USE IN CARCINOGENIC RISK ASSESSMENTS. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/R-92/134.
Description:
As an extension of the work started in a previous contract (EPA 68-02-4403, April 1988), various approaches for estimating the carcinogenic potency of polycyclic aromatic hydrocarbons (PAH) mixtures were investigated. he approach uses the two-stage model described in the previous contract work to convert the tumor incidence data in a variety of bioassays to a low-dose linear slope of the dose-response curve. he potency of mixtures and components of mixtures is expressed as a fraction of the potency of benzo(a)pyrene (B[a]P) which is treated as a reference standard. The basic assumption of the method is that the relative potency of the mixture is the weighted average of the relative potency of the components. his method is applied to data generated by a single group of investigators on lung cancer in female Osborne-Mendel rats induced by implantation of test material in the lung. iesel engine exhaust, gasoline engine exhaust, flue gas condensate from coal-fired furnaces and sidestream cigarette smoke were tested, along with their identified chemical components and solvent-extracted components. f nine different procedures for evaluating the relative potency of combustion product mixtures from their components, the most accurate one assumes that the relative potency of the solvent-extracted fraction containing greater than three rings is equal to B[a]P. lthough this procedure slightly overestimates the potency of the mixture, it is more accurate than the procedures for averaging the relative potencies of the standard set of indicator compounds. he latter procedure, which has been under consideration as the preferred approach, underestimates the potency of the mixtures.