…of biological oxidation by the cytochrome P-450 enzyme system in the liver, benzene and polycyclic aromatic hydrocarbons undergo epoxidation of their ring. The epoxides that form react with deoxyribonucleic acid (DNA), and it is believed that this process is responsible for the carcinogenic properties of polycyclic aromatic hydrocarbons.

Oxidation is carried out by cytochrome P-450 monooxygenases, mixed-function amine oxidases, and alcohol and aldehyde dehydrogenases. The reactions mediated by cytochrome P-450 monooxygenases can make the chemical less toxic or more toxic. The cytochrome P-450 enzymes can, for example, produce epoxides of some chemicals, which are very reactive and can…