Pyrene is a polycyclic aromatic hydrocarbon consisting of four benzene rings fused together in a planar aromatic arrangement which approximates a rhombus in shape.
The metabolism of the tobacco smoke procarcinogen benzo[a]pyrene involves three distinct steps - the introduction of an epoxide group in the 7,8-position, its hydration to a vicinal diol and the introduction of an epoxide in the 9,10-position [REF].