Lung Cancer Mortality and Styrene Exposure in the Reinforced Plastics Boatbuilding Industry: Evaluation of Healthy Worker Survivor Bias.

Abstract

The evidence of styrene as a human lung carcinogen has been inconclusive. Occupational cohorts within the reinforced plastics industry are an ideal population to study this association due to relatively high levels of exposure to styrene and lack of concomitant exposures to other known carcinogens. However, healthy worker survivor bias (HWSB), where healthier workers stay employed longer and thus have higher exposure potential, is a likely source of confounding bias for exposure-response associations, in part due to styrene s acute effects. We studied a cohort of 5163 boatbuilders exposed to styrene in Washington state employed between 1959 and 1978; prior regression analyses demonstrated little evidence for an exposure-response between styrene exposure and lung cancer mortality. Based on estimates of necessary components of HWSB, we found evidence for a potentially large HWSB. Using g-estimation of a structural nested model to account for HWSB we estimated that one year of exposure >30 ppm accelerates time to lung cancer death by 2.3 years (95% Confidence intervals=1.53, 2.94). Our results suggest possibly strong HWSB in our small cohort and indicate that large, influential studies of styrene exposed workers may suffer similar biases, warranting a re-assessment of the evidence of long-term health effects of styrene exposure.