BPDE, or Benzo[a]pyrene diol epoxide, is a metabolic derivative of the polycyclic aromatic hydrocarbon (PAH) benzo[a]pyrene. BPDE is recognized for its high reactivity and is considered a potent carcinogen. It is formed in the body through a series of enzymatic reactions involving cytochrome P450 enzymes, specifically CYP1A1 and CYP1B1.