Antimutagenic effects in humans.

The application of antimutagenicity studies to human somatic mutation is discussed, with emphasis on the potential for future studies. Five assay-gene combinations are now available for measuring human somatic mutation in lymphocytes and erythrocytes. Results with these combinations have defined the human background levels, and show clear responses of mutant frequency to a variety of mutagens. The testing of antimutagenic effects on background frequencies is feasible, but has not yet been done. The major uncertainty in such studies is the unknown age of mutant cells in the background, since only the newly forming mutants are potentially susceptible to most antimutagenic treatments. Intervention studies in the face of active mutagenicity and the use of other genotoxicity endpoints, such as chromosome aberrations, micronuclei and DNA adducts, are considered briefly.