Exposure to high concentrations of nitrosamines and cancer mortality amonga cohort of rubber workers

Objectives-To examine if the occurrence of different cancers was increased among rubber workers, as the highest known exposures of humans to nitrosami nes have occurred in the rubber industry. Methods-A cohort of 8933 rubber workers (hired after 1 January 1950, still active or retired on 1 January 1981 and employed for at least 1 year in one of five study factories) was followed up for mortality from 1 January 1981 to 31 December 1991. Work histories were reconstructed with routinely docu mented cost centre codes, which allowed identification by employment in spe cific work areas. For each cost centre code time and factory specific, semi -quantitative exposures to nitrosamines (three levels: low, medium, high) a nd other compounds were estimated by industrial hygienists. Rate ratios for medium (RRm) and high (RRh) exposures and 95% confidence intervals (95% CI s) were calculated with Cox's proportional hazards models with the low expo sure as reference. Results-Exposure to nitrosamines was significantly associated with an incre ased mortality from cancers of the oesophagus (13 deaths: RRm 1.7, 95% CI 0 .3 to 10.3; RRh 7.3, 95% CI 1.9 to 27.8) and of the oral cavity and pharynx (17 deaths: RRm 0.8, 95% CI 0.2 to 4.1; RRh 3.9, 95% CI 1.4 to 11.1). A no n-significant trend of increasing mortality with exposure to higher concent rations of nitrosamines was found for mortality from cancer of the prostate (26 deaths: RRm 1.4, 95% CI 0.5 to 3.8; RRh 2.2, 95% CI 0.9 to 5.6), and t he brain (six deaths: RRm 3.9, 95% CI 0.3 to 42.6; RRh 6.0, 95% CI 0.6 to 5 7.6). No association was found between exposure to nitrosamines and cancer of the stomach (RR, 0.8, 95% CI 0.4 to 1.8; RR, 1.2, 95% CI 0.5 to 2.5) or lung (RR, 1.0, 95% CI 0.6 to 1.5; RR, 1.0, 95% CI 0.7 to 1.6). Conclusions-Exposure to high concentrations of nitrosamines is associated w ith increased mortality from cancers of the oesophagus, oral cavity, and ph arynx, but not with increased mortality from cancers of the stomach or lung .