Biological effects observed in mammals maintained in an area of very high natural radioactivity

Male rabbits (Oryctolagus cuniculus) were maintained for a 28-month period on the floor of a hut built at a site in southwestern France where the dose rate from natural radioactivity amounts to about 8 mrad/h. Male and female BALB/c mice (Mus musculus) were also placed in the hut during the summer period. The observations of those animals demonstrate that exposure to high natural radiation can increase the frequency of chromosome aberrations in somatic cells and also indicate that fertility in males and females is affected in an inverse manner. Model experiments with radon exposure of laboratory rabbits under controlled conditions have shown that the chromosome aberrations observed in somatic cells are not due to the radon exposure but essentially to gamma irradiation.