CYP1A1 encodes aryl hydrocarbon hydrolase (AHH), an enzyme involved in the production of reactive epoxide intermediates from environmental contaminants such as polycyclic aromatic hydrocarbons (PAHs), polyhalogenated aromatic hydrocarbons (PHAHs) (e.g. dioxin-like compounds and PCBs) and steroid hormones (7,9) that might increase the risk of oxidative stress and cancer. The gene discussed is CYP1A1; the disease is cancer.