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Genetic effects were studied in house mice caught from 1986 to 1994 in regions polluted by radionuclides as a result of the Chernobyl disaster. The dose rates of gamma-radiation on the soil surface ranged from 0.0002 to 2 mGy/h. The frequency of reciprocal translocations in mouse spermatocytes was relatively low, but increased with the dose rate. Embryo mortality was increased only in the progeny of male mice in males caught in 1987 in the area with maximal contamination. The frequency of mice heterozygous for recessive lethal mutations decreased with time after the accident.

A comparative estimation of the frequencies of genetic disorders induced in germ cells of male mice by a single or long-term exposure to incorporated 137Cs or to external gamma-radiation has been carried out. The frequencies of dominant lethal mutations induced by a single exposure were similar with both types of radiation. In stem cell spermatogonia the frequency of reciprocal translocations was significantly lower in the case of single 137Cs administration than upon external gamma-radiation. Upon long-term administration the genetic efficiencies of both types of radiation were similar.

Induced reciprocal translocations in spermatocytes of mice, either caught or exposed at the site, were observed at all levels of radioactive contamination around the Chernobyl nuclear power station. The frequency of reciprocal translocations was relatively low and increased linearly with increasing dose rate. Among 74 male mice exposed as early embryos, four reciprocal translocation heterozygotes were found. Furthermore, an increase in embryonic mortality and frequency of abnormal sperm heads was observed after termination of exposure, but these decreased rapidly with post-exposure time.

The genetic effect of incorporated radiocarbon was studied after single, long-term (33 days) and chronic (6 and 12 months) treatment of male mice (CBA X C57B1) F1 with [14C]glucose. The genetic effect in male germ cells was estimated by 3 tests: DLM frequency in post- and pre-meiotic cells, RT frequency in stem spermatogonia and frequency of abnormal sperm heads. Absorbed doses in the gonads were: 0.22, 0.50 and 1.01 Gy, after a single exposure; 0.74 and 1.47 Gy, after long-term exposures; and 0.006 and 0.031 Gy, after chronic exposure for 6 months; and 0.013 and 0.066 Gy, for 12 months. The results suggest that DLM frequency in post-meiotic cells increased linearly with increasing the dose of 14C single and long-term exposures at a dose of 1.47 Gy only. A chronic treatment with [14C]glucose induced no increase in DLM frequency. RT frequency in stem spermatogonia was statistically significantly higher than the control level after the single and long-term exposure to 14C. A comparison of the results with the results of external single and chronic gamma-irradiation allows the conclusion that the relative genetic efficiency of radiocarbon as compared with that of gamma-rays is about 1.