**12. Chemical carcinogens and induced somatic mutations as biomarkers in molecular epidemiology**

Extensive experience of laboratory research in chemical carcinogenesis has provided a solid foundation for the analysis of chemical-specific macromolecular adducts and related somatic mutations in humans as biomarkers of carcinogen exposure. A paradigm for validating causal relationships between biomarkers of carcinogens exposure and a cancer risk biomarker is shown in a number of observations (Wogan et al, 2005). The metabolite, AFB1, a fungal toxin, is a prototypical example of an environmental chemical carcinogen that has been validated using this strategy. Benzo (a) pyrene, a polycyclic aromatic hydrocarbon 4-aminobiphenyl (Vineis and Pirastu, 1997), an aromatic amine dye, and 4-(Nmethyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone, a tobacco-specific N-nitrosamine (Hetch, 1999), are other key examples. The prevalence of Aflatoxin B1 in developing countries makes host resistance mechanism based on micronutrients of great import to reduction of risk of chemical carcinogenesis.
