POTENCY EQUIVALENCY FACTORS FOR SOME POLYCYCLIC AROMATIC-HYDROCARBONSAND POLYCYCLIC AROMATIC HYDROCARBON DERIVATIVES

Potency equivalency factors (PEFs) for cancer induction relative to be nzo[a]pyrene have been derived for 21 polycyclic aromatic hydrocarbons (PAHs) and PAH derivatives based on a data preference scheme. PEFs ha ve been derived only for PAHs with demonstrated carcinogenicity in bio assays. Cancer potency values and inhalation unit risks are presented for four additional carcinogenic PAHs based on expedited risk assessme nts conducted for California's Proposition 65. A much larger number of PAHs and PAH derivatives are considered mutagenic or genotoxic and ma y have limited evidence for carcinogenicity, but these compounds are n ot considered in this evaluation. New cancer bioassay data and possibl y structure-activity analysis may indicate that additional PAHs are ca rcinogenic. Thus, additional PAHs may be identified as potential human carcinogens when such data become available. However, until that time the PEFs proposed for use in risk assessment were estimated only for PAHs currently classified as carcinogens.