Mortality of workers exposed to 2 methyl-4 chlorophenoxyacetic acid.

The authors examined the mortality and cancer incidence of employees at a company which has manufactured, formulated, and sprayed 2 methyl-4 chlorophenoxyacetic acid (MCPA) and other phenoxy acid herbicides. Ninety-eight percent of the 5,784 men employed by the company during 1947-1975 was traced to the end of 1983. The overall mortality of the cohort was less than that of the national population, as was mortality from cancer. When allowance was made for rural residence, the deficit of cancer deaths became a slight excess, but not statistically significantly so. Among workers whose jobs entailed potential exposure to MCPA, there was one death from soft tissue sarcoma (0.6 expected). No further cases of soft tissue sarcoma were registered among living members of the cohort. Three potentially exposed workers died from nasal carcinoma, but this tumor has not previously been associated with phenoxy herbicides and the cluster of cases may have occurred by chance. The findings do not exclude the possibility that MCPA is a human carcinogen, but they suggest that any risk of soft tissue sarcoma is less than that indicated by earlier studies of 2,4,5-T (2,4,5-trichlorophenoxyacetic acid) and 2,4,5-trichlorophenol and is small in absolute terms.