Benzene Exposure Reconstruction for the Pliofilm Cohort (1936-1976) Using Monte Carlo Techniques. P. Williams and D. Paustenbach, Exponent
The PEL and TLV for benzene are based primarily on epidemiology data of the rubber hydrochloride (Pliofilm) workers. Previous assessments of this cohort relied on different assumptions about workplace practices and processes over time, thereby yielding significantly different estimates of benzene dose for certain jobs. Given the inherent limitations and uncertainties involved in estimating historic exposures for this cohort, a probabilistic approach was used to better characterize their level of exposure. Estimated benzene doses at the 50th and 95th percentiles are reported as equivalent 8-hour time-weighted airborne concentrations for 12 job categories from 1936 to 1965 (Akron I and II facilities) and 1939 to 1976 (St. Mary’s facility). We conclude that estimated benzene doses for St. Mary’s workers were highest for four jobs (neutralizer, quencher, knifeman, spreader), typically ranging from about 50 to 100 ppm during 1939–1946, and 10 to 50 ppm during 1947–1976 at the 95th percentile. These doses are about 1.5 times greater than those estimated at the 50th percentile, and 2–3 times greater than for other jobs in the Pliofilm process. Estimated doses for Akron I and II were nearly 2-fold higher than for St. Mary’s; however, there is a significant level of uncertainty in these concentrations. Benzene doses were similar in magnitude to those predicted in earlier assessments of this cohort, however, this analysis suggests that the prior studies over- and under-estimated exposures for some jobs/years. The current estimates incorporate the most likely range of plausible exposure values, thereby providing a better characterization of the potential workplace exposures for this cohort. These data could be combined with the current or future mortality information to calculate a new potency factor for benzene.
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