Mutagens: some possible health impacts beyond carcinogenesis.

Considerable attention is currently being given to the roles of environmental and endogenous mutagens in tumor induction and in tumor progression through the abilities of mutagens to induce one or another kind of somatic mutation. It is proposed here that mutagens, also through induction of somatic mutations, initiate a spectrum of additional, much more common, focal lesions that are important to the human condition. While individually they are of relative insignificance and thus neglected by many clinicians, the functional attributes of these focal lesions have important impacts on human physiology and thus contribute substantially to the process of aging. Additionally, one individual focus may progress to an extent that it produces clinically recognizable symptoms and may even jeopardize the carrier's life. The ultimate and developed expression of these lesions is heterogeneous, is far removed in time from initial induction, and relies on additional host and environmental factors for expression; therefore, the possible role of somatic mutation is readily overlooked. The focal lesions reviewed are fibrous atherosclerotic plaques, senile cataracts, and metaplasias. Literature that implicates metaplasias as precursor or as predisposing lesions in the ultimate formation of gallstones, duodenal ulcers, and adenocarcinomas is summarized.