An adenomatous polyp case-control study to assess occupational risk factors following a workplace colorectal cancer cluster.

To assess potential etiologic factors among a population of Texas polypropylene workers previously found to have an excess of colorectal cancer (concentrated among mechanical and process workers), the authors conducted an adenomatous polyp case-control study. Cases (n = 24) were workers found to have adenomatous polyps during a company-sponsored colorectal cancer screening program, while controls (n = 72) were workers found to be free of polyps. Exposure assessment utilized a thorough industrial hygiene and toxicologic review of operations in conjunction with work activity interviews of cases and controls to develop chemical-specific exposure scores weighted by time, exposure level, and frequency of exposure. Stratified analyses and logistic regression found that cases tended to have higher exposure to pre-extrusion polymer plus additives (odds ratio (OR) = 2.6, 90% confidence interval (CI) 1.1-6.3) and higher exposure to certain finishing additives (OR = 4.8, 90% CI 1.5-15.3). Analyses by job category or area of the plant did not indicate additional risk factors. The exposures identified in this study are discussed in light of the available toxicologic data on these and related compounds. The need for confirmatory experimental and epidemiologic studies is noted.