Biomarkers in metabolic subtyping--relevance for environmental cancer control.

People differ in their susceptibility to particular cancers and in their sensitivity to certain carcinogens. Differences in sensitivity to environmental carcinogens are determined by variations in genetic background--genetic polymorphism. Susceptibility or sensitivity factors can act at any stage in the multistage process of carcinogenesis, from exposure to carcinogens to the clinical appearance of cancer. This paper addresses the use and limitations of studies on human polymorphism for carcinogen metabolizing enzymes and their relevance for cancer control. The practical use of susceptibility and sensitivity markers in cancer control is not yet clear. Some of the potential dangers of their use are job discrimination and genetic exculpation--the 'blame the victim' attitude. Furthermore, an imprudent focus on genetic predisposition could shift the attention from carcinogens in the environment to biological 'defects' in the individual. Although carcinogens act in predisposed subjects, this should not overshadow the fact that most cancers are due to environmental factors, in both susceptible and unsusceptible individuals, and are therefore preventable. Even if individuals differ in their sensitivity to carcinogens, the primary option in cancer control must be to reduce exposure in order to include and protect the most sensitive fraction of the population.