| Section2 = }} Benzo[a]pyrene, C20H12, is a five-ring polycyclic aromatic hydrocarbon that's mutagenic and highly carcinogenic. It is a crystalline yellow solid. Benzo[a]pyrene is a product of incomplete combustion at temperatures between 300 and 600 °C. Benzo[a]pyrene was determined in 1933 to be the component of coal tar responsible for the first recognized occupation-associated cancers, the sooty warts (cancers of the scrotum) suffered by chimney sweeps in 18th century England. In th… (More on Benzopyrene)