Mortality among aircraft manufacturing workers

Objectives-To evaluate the risk of cancer and other diseases among workers engaged in aircraft manufacturing and potentially exposed to compounds cont aining chromate, trichloroethylene (TCE), perchloroethylene (PCE), and mixe d solvents. Methods-A retrospective cohort mortality study was conducted of workers emp loyed for at least 1 year at a large aircraft manufacturing facility in Cal ifornia on or after 1 January 1960. The mortality experience of these worke rs was determined by examination of national, state, and company records to the end of 1996. Standardised mortality ratios (SMRs) were evaluated compa ring the observed numbers of deaths among workers with those expected in th e general population adjusting for age, sex, race, and calendar year. The S MRs for 40 cause of death categories were computed for the total cohort and for subgroups defined by sex, race, position in the factory, work duration , year of first employment, latency, and broad occupational groups. Factory job titles were classified as to likely use of chemicals, and internal Poi sson regression analyses were used to compute mortality risk ratios for cat egories of years of exposure to chromate, TCE, PCE, and mixed solvents, wit h unexposed factory workers serving as referents. Results-The study cohort comprised 77 965 workers who accrued nearly 1.9 mi llion person-years of follow up (mean 24.2 years). Mortality follow up, est imated as 99% complete, showed that 20 236 workers had died by 31 December 1996, with cause of death obtained for 98%. Workers experienced low overall mortality (all causes of death SMR 0.83) and low cancer mortality (SMR 0.9 0). No significant increases in risk were found for any of the 40 specific cause of death categories, whereas for several causes the numbers of deaths were significantly below expectation. Analyses by occupational group and s pecific job titles showed no remarkable mortality patterns. Factory workers estimated to have been routinely exposed to chromate were not at increased risk of total cancer (SMR 0.93) or of lung cancer (SMR 1.02). Workers rout inely exposed to TCE, PCE, or a mixture of solvents also were not at increa sed risk of total cancer (SMRs 0.86, 1.07, and 0.89, respectively), and the numbers of deaths for specific cancer sites were close to expected values. Slight to moderately increased rates of non-Hodgkin's lymphoma were found among workers exposed to TCE or PCE, but none was significant. A significan t increase in testicular cancer was found among those with exposure to mixe d solvents, but the excess was based on only six deaths and could not be li nked to any particular solvent or job activity. Internal cohort analyses sh owed no significant trends of increased risk for any cancer with increasing years of exposure to chromate or solvents. Conclusions-The results from this large scale cohort study of workers follo wed up for over 3 decades provide no clear evidence that occupational expos ures at the aircraft manufacturing factory resulted in increases in the ris k of death from cancer or other diseases. Our findings support previous stu dies of aircraft workers in which cancer risks were generally at or below e xpected levels.