Radiation effects in lymphocytes of children living in a Chernobyl contaminated region of Belarus

Purpose: To investigate cytogenetic and mutational effects in lymphocytes f rom individuals chronically exposed to radiation from the Chernobyl catastr ophe. Materials and methods: Nine years after the Chernobyl accident (1986), peri pheral blood lymphocytes from 20 Kalinkovichi children (age 10-15) and 10 M insk children (age 10-17) were analysed for genetic damage by several assay s. Radiation damage in exposed children was investigated in descendants of progenitor cells that were irradiated during a short period immediately aft er the accident. In the time-span between the accident and brood sampling t he cells were also irradiated chronically by internal radiation originating from ingested radionuclides and, to a smaller extent, by external radiatio n from radionuclides. The parameters measured in whole blood smears were th e frequency of micronucleated mononucleated lymphocytes and binucleated lym phocytes with nucleoplasmic bridges and associated micronuclei. Cultures of cytokinesis-blocked lymphocytes were used to analyse mononuclear and binuc lear cells for the presence of micronuclei, also cell killing effects. A co lony assay was used to study induction of recessive mutations in the HPRT g ene. Results: The analysis of whole-blood smears indicated a doubling of the fre quency of micronuclei per 100 mononuclear lymphocytes in exposed children c ompared with unirradiated children. Small numbers of binucleated lymphocyte s with nucleoplasmic bridges and associated micronuclei were found in blood smears from exposed children. Analysis of cytokinesis-blocked cultures ind icated in mononuclear cells of exposed children a statistically significant increase in the frequency of micronuclei. When the same parameters were st udied in binucleated cells there was no difference between exposed and unex posed children. Results of the dye-exclusion assay showed a four-fold incre ase in the percentage of dead cells between exposed and unexposed children. There was no evidence for induction of HPRT mutations in exposed children. Conclusion: These results indicate that the frequently advocated procedure of simply analysing micronuclei in cytokinesis-blocked binucleated lymphocy tes can result in an underestimate of genetic damage induced by radiation a ccidents. Biodosimetric studies should therefore employ a battery of assays for the detection of several types of genetic damage in different generati ons of lymphocytes.