Difficulties in assessing the human health effect of mutagenic carcinogens by cytogenetic analyses.

The analysis of induced chromosome aberrations in the peripheral lymphocytes of irradiated people is a reliable method for determining exposure to ionizing radiations. The system should also work for S-independent chemicals. For the majority of chemical clastogens, which are S-dependent, however, the utility of the system is far less certain because DNA repair can remove many of the adducts before the cells enter S. Sister chromatid exchanges are sensitive indicators of S-dependent mutagens; however, because of DNA repair, great interpersonal variability of response, and variability of reference populations, it has not yet been proved that they can be used to monitor populations for low-level chronic exposure. In any case, these cytogenetic tests can only be used to estimate the risk to the population as a whole. They cannot be used to predict whether a given person will suffer any particular form of ill health.