Some recent epidemiologic studies have suggested that chlorinated phenoxy acid herbicides are human carcinogens. The mortality experience in a cohort of 1,926 men who had sprayed 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) during 1955-1971 has been followed prospectively from 1972 to 1980. The total phenoxy acid exposure was generally rather low because the duration of work had mostly been less than two months. In 1972-1976 mortality from all natural causes in the cohort was only 54% of the expected value (based on age-specific rates for the general population), and in the succeeding 4-a period 81% of the expected value. In the assessment of cancer, mortality allowance was made for 10- and 15-a periods of latency between the first exposure and the start of the recording of vital status during the follow-up. No increase in cancer mortality was detected, and the distribution of cancer types was unremarkable. No cases of death from lymphomas or soft tissue sarcomas were found. The study results must, however, be viewed with great caution owing to the small size of the cohort, the low past exposure, and the brief follow-up period.

Key terms 2,4-dichlorophenoxyacetic acid; 2,4,5-trichlorophenoxyacetic acid; chlorinated phenoxy acid; Finland; herbicide; herbicide applicator; mortality; prospective cohort study