AN UPDATE OF MORTALITY AMONG CHEMICAL WORKERS POTENTIALLY EXPOSED TO THE HERBICIDE 2,4-DICHLOROPHENOXYACETIC ACID AND ITS DERIVATIVES

Four years of additional mortality follow-up through 1986 are reported for a previously studied cohort of 878 chemical workers who were pote ntially exposed to 2,4-dichlorophenoxyacetic acid (2,4-D) and its deri vatives between 1945 and 1983. Observed mortality was compared with ex pected levels based on death rates of the US population and of 36,804 ''unexposed'' workers from the same manufacturing location. Non-Hodgki n's lymphoma (NHL) was a particular focus of the study because of a su ggested association with 2,4-D exposure in some case-control studies. For the total observation period, the standardized mortality ratios fo r all causes and for malignant neoplasms were 92 and 91, respectively. Analyses using the internal comparison group yielded virtually identi cal results. The initial study had found two deaths from NHL, both of which occurred under circumstances (ie, short latency and modest expos ure) which made it less plausible that they were related to 2,4-D expo sure. No new deaths from NHL were observed in the extended follow-up p eriod and mortality for this cause showed a nonstatistically significa nt excess (standardized mortality ratio, 196; 95% confidence interval 24 to 708) for the total observation period. Analyses by production ar ea, and by two different measures of exposure, combined with two diffe rent approaches to account for latency, did not show patterns suggesti ve of a causal relationship between exposure to 2,4-D or its derivativ es and any particular cause of death.