RECORDING OF EXTERNAL RADIATION EXPOSURES AT OAK-RIDGE-NATIONAL-LABORATORY - IMPLICATIONS FOR EPIDEMIOLOGIC STUDIES

Accurate measurements of radiation exposure for individuals are critic al to assessing radiation-mortality associations. This paper is based on a study of changes in recorded doses and in radiation monitoring pr ograms at Oak Ridge National Laboratory, a U.S. Department of Energy f acility where whole body external penetrating radiation exposures have been of primary epidemiological interest. External radiation monitori ng data from 1943-1984 are analyzed for a group of white males (N = 8, 318). The proportion of workers monitored for external radiation incre ased from about 50% in 1943 to over 80% in 1944 to above 98% after 194 8. Mean radiation doses showed maxima in 1944 and 1957, followed by st eady and long-term declines. Numerous changes in monitoring programs o ccurred during the study period, including changes in the types of dos imeters used, the frequency of reading dosimeters, methods of calculat ing doses, and practices of recording doses. Temporal patterns of dose s in the lower range of the distribution showed some changes suggestiv e of changes in policies and practices for recording doses, which woul d influence dose values used in epidemiological studies. Reliable and accurate exposure measurements are especially important in studies of low level exposures due to small differences in outcomes between expos ure groups. Evidence of changes in recorded doses due to monitoring an d recording practices, rather than to actual changes in exposures in t his well-monitored population, suggests the importance of comparable s tudies of other populations used for epidemiological studies of radiat ion-mortality associations.