UPPER RESPIRATORY CANCER AMONG REFINERY AND CHEMICAL PLANT WORKERS: A CASE-CONTROL STUDY IN BATON ROUGE, LOUISIANA

Upper respiratory cancer (URC) specific to workers employed on an ethanol unit at a large southern United States refinery and chemical plant was associated with exposure to strong concentrations of sulfuric acid used as a reactant in this process (Lynch et al., 1979). The carcinogen implicated by indirect evidence was diethyl sulfate. However, additional URC cases were subsequently found that could not be associated with employment on the former ethanol unit. This fact, together with the continued use of sulfuric acid in strong, intermediate, and weak concentrations in the same industrial complex, motivated the present investigation. In particular, hypotheses concerning an association between laryngeal cancer and industrial exposure to the three concentrations of sulfuric acid present in the complex have been tested. The study is a multiple-matched case-control design with a minimum of three controls individually matched to each case on race, sex, date of birth, date of initial employment and duration of employment. Extensive case ascertainment procedures identified 50 confirmed cases of URC, 34 of which were laryngeal carcinomas. Criteria for case inclusion required employment at the company site for a minimum of 12 continuous months and a diagnosis of URC during the period July, 1944 through August, 1980. The study was based on existing medical and employee relations\u27 work history records. Retrospective estimates of exposure were made without regard to case-control status. Conditional logistic regression techniques were supported by other statistical methods in the analysis. Significant confounders that were controlled included tobacco use, alcoholism and a prior history of ear, nose, and throat disease. Summary worklife exposure, quantified in terms of a mean grade, was shown to be the most discriminating exposure measure for this study design. Results indicate significant associations between sulfuric acid exposure and URC with odds ratios exceeding four. Strong collinearity among the three acid concentrations has rendered any separation of independent acid strength effects impossible. None of the other exposures examined in this study, including asbestos, nickel or wood dust, revealed significant associations. There is a strong possibility that the association is specific for laryngeal cancer. Further research is indicated