Risk assessment for benzo[a]pyrene.

Benzo[a]pyrene is the most studied carcinogenic polycyclic aromatic hydrocarbon and one of the most potent, and it is often used as a toxicological prototype or surrogate for all carcinogenic polycyclic aromatic hydrocarbons. Quantitative risk assessment of benzo[a]pyrene has been hampered by the quality of the data sets available for quantitation. The EPA has calculated both potency slopes and unit risks using the linearized multistage model. We have confirmed and refined that analysis. Risks based on feeding, inhalation, and intratracheal administration of benzo[a]pyrene show fairly good concordance. Others have applied the Moolgavkar two-stage model to the data and estimated a lower potency for benzo[a]pyrene. We think that such conclusion is premature. Longer term exposures of animals to benzo[a]pyrene are necessary to provide the data needed for more refined carcinogenic risk estimations.