[Transgenerational effects of parental exposure to ionizing radiation]

The deleterious effects of exposure to ionizing radiation on human health have been known for many years. The main long term effect of this exposure is an increase in the risk for developing benign and malignant tumors in the exposed population. This review summarizes the existing data on the possible effects of ionizing radiation on the second generation, focusing on cancer risk. The two mechanisms through which parents' exposure to radiation could affect their children's health are intrauterine exposure of the fetus and preconception exposure of the gonads. Intrauterine exposure to ionizing radiation has teratogenic and carcinogenic effects. Most case-control studies have shown a 40-50% increase in the risk of cancer following intrauterine exposure to medical diagnostic radiation at doses of 10-20mGy. Results of these studies have greatly contributed to the strict radiation protection guidelines at pregnancy existing today. Although animal studies have shown that gonadal exposure to high doses can cause heritable genetic changes, this effect has not been demonstrated unequivocally in epidemiological studies. A case-control study suggested an association between preconception irradiation and leukemia/non-Hodgkin's lymphoma in children of male workers at a nuclear plant in the UK (the Gardner hypothesis). This report generated substantial interest and research; however, subsequent occupational studies failed to confirm the association. Negative results were also reported in studies of the atomic bomb survivors and survivors of childhood cancer. In summary, epidemiological studies do not support the association between gonadal exposure to ionizing radiation and the development of cancer and other genetic diseases among offspring.