Retrospective study of the relationship between agricultural use of 2,4,5‐T and cleft palate occurrence in Arkansas

The relationship between use of the herbicide 2,4,5‐T in Arkansas and the concurrent incidence of facial clefts in children was studied retrospectively. Pertinent animal studies of the toxicity of 2,4,5‐T, and related compounds were reviewed; embryotoxic and teratogenic effects, including cleft palate, have been noted in several mammalian species. Although newspaper articles appeared linking defoliant use with increased birth anomalies in South Vietnam in 1969, human epidemiology studies have not established a causal relationship between use of 2,4,5‐T and birth defects. We felt that additional information concerning the human problem was needed to complement the experimental animal data, so we analyzed facial cleft rates and concurrent estimated use of 2,4,5‐T in Arkansas during 1948‐1974. Estimated level of exposure to 2,4,5‐T was determined by categorizing the 75 Arkansas counties into high‐, medium‐, or low‐exposure groups on the basis of their rice acreage during 6‐ or 7‐year intervals beginning in 1943. A total of 1,201 cases of cleft lip and/or cleft palate for these 32 years was detected by screening birth certificates and checking the records of the Crippled Children's Services. Facial cleft rates, presented by sex, race, time period, and exposure group, generally rose over time. No significant differences were found for any race or sex combination. We believe that the general increase seen in facial cleft incidence in the high and low‐exposure groups is attributable to better case finding rather than maternal exposure to 2,4,5‐T.