A cancer incidence and mortality study of Dow Chemical Canada Inc. manufacturing sites.

Background: Previously, the mortality was reported in a cohort of male workers at an Ontario chemical plant.

Aims: To expand the cohort and to investigate the mortality and cancer incidence risk among chemical manufacturing sites.

Methods: We followed 5277 men and 1301 women from 1950 to 1999.

Results: Employees experienced lower mortality and cancer incidence rates than the general population for several major causes of death, including heart disease, respiratory cancer and many other cancers. There were no cases of angiosarcoma of the liver. We observed a lower mortality rate of prostate cancer [standardized mortality ratio = 0.79, 95% confidence interval (CI) 0.43-1.32], but a higher incidence rate of prostate cancer [standardized incidence ratio (SIR) = 1.22, 95% CI 1.00-1.48]. Among the Sarnia employees, the incidence of pleural neoplasms was increased (5 observed versus 1.48 expected, SIR = 3.37, 95% CI 1.09-7.86). These cancers were included in the 12 deaths with malignant mesothelioma at Sarnia.

Conclusion: Consistent with the earlier report, lower mortality rates were observed for the major classifications of disease and malignant neoplasms. The higher incidence rates of prostate cancer are not readily explainable but may reflect increased screening among current employees and recent retirees. Past asbestos exposure prior to 1980 is probably a contributor to the deaths due to malignant mesothelioma but is not reflected in lung cancer mortality. We find little indication of any other increased rates of mortality or cancer within the overall workforce of these chemical plants.