Mortality among workers at a nuclear power plant in the United States.

A second follow-up of 9,000 workers at the Calvert Cliffs Nuclear Power Plant (MD, USA) identified 346 deaths in the years 1969-88, 101 of which were attributed to malignant neoplasms. The original study had the primary purpose of assessing the feasibility of studies of workers based upon individual plant and Nuclear Regulatory Commission records. The average, cumulative, occupational dose through 1984 was low, only 21 mSv, but ranged up to 470 mSv, with 12 percent of the workers receiving more than 50 mSv. Mortality from most causes of death was low and there was a deficit of deaths from diseases of the circulatory system. Ionizing radiation exposures were not related to the probability of death from neoplasms generally or from any specific form of cancer. There were only two deaths from leukemia, whereas four were expected at population death rates. Larger numbers of workers, followed for longer periods of time, are needed to determine the mortality risk to workers in the nuclear power industry. The difficulties in obtaining dose information for transient workers were so great, and so time consuming, as to make questionable the practicability of studying the workers at a large number of power plants in this way.