Retrospective noise estimates for British nuclear workers using an alternative approach.

Exposure estimates were required to support an epidemiological study of occupational noise and cardiovascular disease. The study cohort consisted of male industrial workers employed at two nuclear facilities in England between 1945 and 1999 (n=2412). Historical noise exposure data were available from 6850 sound pressure measurements collected since 1965. Additional information was obtained from interviews with retired and long-term company personnel. Partly due to the lack of information provided by job title, coupled with the fact that noise behaves differently compared with chemical agents, an unusual approach was used to estimate noise exposure. Rather than grouping homogeneous exposure groups by job title or task, the assessors first used historical sampling data to estimate average area noise levels in each workplace where a survey had been performed. Noise contours were then estimated in the work area and, finally, individual estimates of exposure were further refined based on job title. Estimates were extrapolated to areas where noise surveys were not performed and adjustments were made for potential bias. Overall, noise exposure estimates ranged from 60 to 97 dBA, with a median of 86 dBA. For use in subsequent exposure-response analysis, cohort work histories were used to calculate exposure indices of cumulative, average intensity and exposure duration above 85 dBA. Validation exercises are discussed.