AN ANALYSIS OF THE RELIABILITY OF SELF-REPORTED WORK HISTORIES FROM ACOHORT OF WORKERS EXPOSED TO POLYCHLORINATED-BIPHENYLS

An investigation was conducted to examine the reliability (reproducibi lity) of self reported occupational histories obtained from a cohort o f 326 capacitor manufacturing workers who had participated in an epide miological study relating health abnormalities to exposure to polychlo rinated biphenyls (PCBs). For a subsample of the cohort (n = 164) in w hich occupational histories were obtained twice (in 1976 and 1979), re liability of cumulative exposure to PCBs ranged from 93-6% for the ear ly PCB period (1947-70) to 95.7% for the late PCB period (1971-6). The se respective reliabilities were lower, however, for workers who chang ed jobs often. Workers above the median value of a weighted job change index had early and late reliabilities of 89.9% and 83.6% respectivel y. Reliability is a relevant factor when calculating power or sample s ize during the planning stage of epidemiological studies, for interpre tation or adjustment of estimates in the analysis stage, or for determ ination of study feasibility.