benzoapyrene

Benzo[a]pyrene, commonly spelled benzo[a]pyrene, is a polycyclic aromatic hydrocarbon (PAH) with the chemical formula C20H12. It consists of five fused benzene rings in a planar, hydrophobic structure. BaP is produced by incomplete combustion of organic matter and is found in tobacco smoke, grilled or charred foods, vehicle exhaust, coal and wood smoke, and various industrial emissions. It tends to adhere to airborne particulates and can accumulate in soils and sediments.

BaP is not produced intentionally in large amounts but forms as a byproduct of high-temperature processes such as combustion. Environmental exposure occurs through inhalation of polluted air and ingestion of contaminated food or water. Because it binds strongly to particles, indoor air quality and occupational settings with combustion emissions are important exposure pathways.

Metabolism of BaP involves activation by cytochrome P450 enzymes to reactive metabolites, notably benzo[a]pyrene diol epoxide (BPDE). BPDE forms covalent adducts with DNA, especially at guanine bases, which can cause mutations and contribute to carcinogenesis if not repaired. BaP is one of the most studied carcinogenic PAHs and serves as a biomarker for PAH exposure in many studies.

Health effects and regulation: The International Agency for Research on Cancer (IARC) classifies BaP as a Group 1 carcinogen (carcinogenic to humans). Associations are strongest for lung cancer in smokers and workers exposed to PAHs, with risk modulated by dose and co-exposures. Regulation often uses BaP as a marker of PAH pollution in environmental monitoring, foods, and air quality guidelines.

Detection and biomarkers: Exposure can be assessed by BaP-DNA adducts or urinary metabolites such as 3-hydroxybenzo[a]pyrene; 1-hydroxypyrene is a broader PAH biomarker. Environmental monitoring routinely includes BaP as a representative PAH.