Benzo(a)pyrene [B(a)P] is a polycyclic aromatic hydrocarbon (PAH) having five aromatic rings in a fused, honeycomb-like structure. Its formula and molecular weight are C₂₀H₁₂ and 252.30, respectively. It is a naturally occurring and man-made organic compound formed along with other PAH in incomplete combustion reactions, including the burning of fossil fuels, motor vehicle exhaust, wood products, and cigarettes. It is classified as a known human carcinogen by the EPA, and is considered to be one of the primary carcinogens in tobacco smoke. Synthesized in 1933, it was the first carcinogen isolated from coal tar and often serves as a surrogate compound for modeling PAHs.