Cytogenetic and genetic effects of continuous irradiation at a low exposure rate

We followed the frequency of chromosome aberrations in bone marrow cells of mice continuously irradiated from a 60Co source at an exposure rate of 4.785 mGy/day (0.5R/day) for 140 days. The frequency of chromosome aberrations increased to 4.8% already at day 10 of irradiation and was stabilized at 2--3% in the period from 60 to 140 days. No increase in the frequency of reciprocal translocations and dominant lethal mutations induced in spermatogonia during irradiation was, however, observed.