A retrospective follow-up study of mortality among triazine herbicide-manufacturing workers

This retrospective follow-up study evaluated the mortality experience of 1,472 workers at a triazine herbicide-manufacturing plant in Louisiana. Subjects were all employees who had worked in production-related jobs for at least 6 months before January 1, 1987.

Ascertainment of vital status was accomplished as of January 1, 1987, for 99% of the cohort. The overall and cause-specific observed numbers of deaths among the workers were compared with the numbers expected on the basis of U.S. general population mortality rates.

The mortality rates for all causes combined and for all major cause of death categories, except cancer, were markedly lower than those of the general U.S. population. Overall, there were 13 observed deaths, compared with 28 expected (standardized mortality ratio (SMR) = 46, 95% confidence interval = 24-74). The SMR for all cancers combined was 82 (15-201). The only statistically significant result for specific cancers was a larger than expected number of deaths from non-Hodgkin's lymphoma (observed/expected = 2/0.2, p = 0.02).

The low mortality rate for all causes combined may be due to the "healthy worker effect." The time since starting work was less than 10 years for 72% of the subjects as of the end of the follow-up period, and 38% of the cohort was actively employed at the end of the study.

The increase in mortality from non-Hodgkin's lymphoma is based on only two observed deaths. Although this result is statistically significant, chance or confounding by some unknown factor can not be ruled out as possible explanations. Future observation of the present cohort and of other groups of workers exposed to triazine herbicides will be necessary to elucidate the relationship between exposure to triazine herbicides and the development of non-Hodgkin's lymphoma.