Benzo[a]pyrene

Benzo[a]pyrene is among the best-known polynuclear hydrocarbons, characteristically found in cigarette smoke and tar. The compound is listed by the NTP as a known human carcinogen.

Mutagenicity. Mutagenic in the Ames test and the umu test. The metabolite BPDE (benzo[a]pyrene-7,8-dihydrodiol-9,10-epoxide) is the major mutagenic and carcinogenic species.

Carcinogenicity. B[a]P induces tumors in mammary glands, forestomach, lungs, skin, trachea, bronchi, liver, abdomen and uterus across multiple species, depending on the route of administration. The compound is used in animal testing to induce cancers for evaluating anticancer activity of other substances.

Exposure must be minimized. Rectified cade oil, in which most polynuclear hydrocarbons are removed by fractional distillation, is considered safe by IFRA for fragrance use.

Many polynuclear hydrocarbons including B[a]P are bioactivated by hepatic CYP enzymes to highly reactive, potently carcinogenic epoxides. Instillation of B[a]P into the rat nasal cavity led to transport of the compound or its metabolites along olfactory neurons to the olfactory bulb.

Unrectified cade oil is one of few essential oils with meaningful B[a]P levels. Fractional distillation removes most polynuclear hydrocarbons during refinement.