Reference values for chromosome aberrations in human lymphocytes as indicators of genotoxic effects

Increased chromosome aberrations (CA) in human cultured lymphocytes are an accepted indicator of early biological effects of exposure to genotoxic agents, which has also been investigated, with conflicting results, in several groups of subjects occupationally exposed to metals known or suspected to be carcinogenic. One of the problems with this indicator is the lack of universally accepted reference values. Difficulty in establishing absolute reference values for CA depends on individual variability in the reference groups (due to several environmental and genetic confounding factors) and on methodological variants at the different stages of the test (culture methods, scoring, classification and reporting of CA). Therefore, at present, CA studies in exposed groups should include proper 'control' groups, matched for the known confounders, investigated in the same laboratory, with the same methods in order to minimize factors of variation. The results of the studies should be statistically compared and evaluated mainly on a group basis.