Follow-up in the micronucleus frequencies and its subsets in human population with chronic low-dose gamma-irradiation exposure

Forty-eight individuals, who received protracted low-dose rate gamma-irradi ation from radioactive environments for 2-10 years, have been evaluated rep etitively for cytogenetic damage by the cytochalasin-B micronuclei assay (C BMN) after they relocated from radioactive buildings. These subjects were s hown to have a significant decrease in the CBMN frequencies during 26.2 +/- 8.4 months of follow-up. By the mixed effect multiple linear regression an alysis, the CBMN frequencies in these 48 subjects during repetitive measure ments were significantly associated with the relocation duration since leav ing the radioactive environments (relocation time or RT in months; estimate -0.47, standard error 0.0016, p value 0.0074). The alteration rate in the proportions of binucleates carrying a single micronucleus and those with mu ltiple micronuclei was further compared among 26 of these exposed individua ls. The proportions of binucleates with multi-micronuclei were shown to dec line significantly faster than those with a mono-micronucleus between these two repetitive assays (proportional Z-test, p value 0.003). Moreover, some of the exposed subjects were shown to have a persistent increase in the to tal micronuclei frequencies or carrying multi-micronuclei in the binuclei e ven 3-4 years post-cessation of exposure. This suggests potential genomic i nstability in stem cells of the exposed individuals and the phenomenon dese rves further closer monitoring. Understanding the dynamics of micronucleus expression in lymphocytes in subjects with previous mutagenic exposure woul d be of significant importance for human population monitoring. (C) 1999 El sevier Science B.V. All rights reserved.