Risks of radiation at low dose rates.

Cancer mortality has been studied in 1110 women who worked in the U.K. with paint containing radium from 1939 to 1961. Their body contents of radium were small, but they were also irradiated externally by gamma-rays to receive absorbed dose rates of 1-4 mGy per week. Those in the group who were under 30 years of age when they started work show a significantly increased risk of dying from breast cancer. If the excess were due solely to their radiation exposure, it would represent a risk of 20-500 deaths from breast cancer per 10(4) women exposed to 1 Gy, which is consistent with the value used by the International Commission on Radiological Pretection.