Scoping review of polycyclic aromatic hydrocarbons (PAH) human and experimental animal cancer studies

Abstract

Background: The carcinogenicity of some PAHs has not been evaluated. To gauge feasibility of a potential systematic review of PAH cancer hazard, we conducted a scoping review on PAH cancer studies.Methods: We searched PubMed for human cancer studies and mapped them by exposure source and cancer type. For animal studies, we searched three databases for PAHs in general and 35 specific PAHs, excluding PAH listed in the Report on Carcinogens; studies were mapped by PAH, exposure route, and cancer sites.Results: Human cancer studies assessed exposure to PAH mixtures or surrogates from (1) the workplace using expert assessment or job exposure matrices, (2) the environment by measuring or modeling indoor or outdoor PAH exposure, or (3) all sources by measuring PAH biomarkers. Occupational studies reported lung and urinary bladder cancers most often, but also head and neck, pancreas, and other cancers. Environmental studies reported breast cancer, childhood leukemia, and others. Biomonitoring studies using PAH urinary biomarkers reported lung and breast cancers. Biomonitoring studies using PAH adducts, some including gene-environment interaction, reported lung, breast, and liver cancers.We selected animal studies using physiologically relevant exposures (oral, dermal, inhalation, intratracheal instillation, or IP injection). Laboratory animals were tested with individual PAHs. Most were mouse studies with dermal applications, and many reported skin cancer. The similar study of different PAHs could facilitate PAH comparisons. IP studies in mice reported lung and liver cancer. Anthracene, benzo[ghi]perylene, chrysene, cyclopenta[cd]pyrene, fluoranthene, and pyrene had increased cancer at two or more sites. Anthracene, chrysene, and benzo[c]fluorene has increased cancer via two exposure routes. No cancer sites were reported from the three rat studies with relevant exposures.Discussion: Both human and animal cancer literature are sufficient for systematic review of PAH cancer hazard. Integrating human cancer evidence across exposure scenarios will inform future assessments.