Cancer mortality among workers of a synthetic textiles plant in Quebec

This thesis describes a retrospective cohort study of cancer mortality among employees of the Celanese Canada Inc. synthetic textiles plant in Drummondville, Quebec. The study was commissioned by the company to confirm or refute a previous observation (Vobecky et al., Cancer 54:2537-2542, 1984) that there were higher mortality rates from colorectal cancer among male employees of the textiles unit, the cellulose acetate fiber manufacturing unit, and the cellulose triacetate and polypropylene extrusion units and to investigate whether mortality rates for other sites of cancer were associated with employment in each area of the plant and with occupational exposures.Workers with more than one year experience at the plant were eligible for study if they were employed on January 1, 1947 or if they were newly hired between that date and December 31, 1977. Vital status as of December 31, 1986 was ascertained for 7,422 men and 2,720 women through a probabilistic record linkage to the Canadian Mortality Data Base. Among men, there were about 220,000 person-years of observation and 1,738 deaths and, among women, there were about 89,000 person-years of observation and 241 deaths.Three reference regions were used to derive standardized mortality ratios (SMR): the entire Province of Quebec, semi-rural regions of the Province, and the area in which the plant is located. Results based on rates for these regions were generally similar. For men, the SMR for all causes of death was significantly less than unity (SMR = 0.71, 95%CI:0.68-0.74), as were the SMRs for most sites of cancer (SMR all neoplasms = 0.73, 95%CI:0.66-0.80). The SMR for colorectal cancer was 0.68 (95%CI:0.51-0.91). Of the 20 cancer sites examined in men, reticulum cell sarcoma was the only one having a significantly elevated SMR, and this occurred only among the subcohort of men hired prior to 1947 (SMR = 2.84, 95%CI:1.04-6.18, 6 deaths). For women, the SMR for all causes of death was 0.75 (95%CI:0.66-0.85) and there were moderately elevated SMRs for a number of sites of cancer, but none were significantly greater than expectation (SMR all neoplasms = 0.97, 95%CI:0.80-1.17).SMRs were also calculated according to employment in each processing unit and exposure to occupational agents, and case-control analyses were carried out within the cohort for selected sites of cancer. Of the scores of associations tested, very few were significantly elevated. There were excesses of biliary cancers and non-Hodgkin's lymphomas among workers in the cellulose acetate fiber manufacturing unit. There were also significant associations between stomach cancer and exposure to cutting oils, and between prostate cancer and exposure to glycol monobutyl ether. However, none of these associations were persuasive.With regards to colorectal cancer, there was a nonsignificant elevation in risk among workers who had ever worked in the polypropylene and cellulose triacetate extrusion unit (OR$ sb{ rm e}$ = 2.3, 95%CI:0.5-9.9) but there was no apparent increase in risk with increasing duration of employment. Thus, the evidence for an association was not convincing. For the cellulose acetate fiber manufacturing unit, the evidence of an increase, although based on few cases, was slightly more persuasive (OR$ sb{ rm e}$ = 1.9, 95%CI:1.0-3.6), but no trend was observed with duration. No association was observed with employment in the textiles unit (OR$ sb{ rm e}$ = 1.1, 95%CI:0.6-2.2) nor were there any noteworthy associations between colorectal cancer and any of the agents evaluated in the case-control analyses