Assessment of colorectal cancer screening outcomes among workers involved in polypropylene manufacture.

To follow up on a previous finding of an elevated colorectal cancer incidence rate among Exxon employees on a unit devoted to the manufacture of polypropylene (the polyolefin unit (POU)), a company-sponsored screening program was offered to all former and present POU workers. Overall participation was 52.5%, with lower participation among older workers and workers who had retired or were no longer employed by the company. Evaluation of polyp prevalence rates for POU workers v rates for non-Exxon employees screened at the same clinic showed a general pattern of elevated rates for POU employees, especially for mechanical and process workers. This pattern was most marked for polyps at least 0.5 cm in diameter, but findings were less clear for adenomatous polyps. The effect of factors that might bias evaluation of colorectal polyp prevalence rates (eg, selection bias, observation bias, genetic susceptibility) is discussed, but none of these factors seemed a likely explanation for the findings observed in this study.