The Excretion of Dieldrin, DDT, and Heptachlor Epoxide in Milk of Dairy Cows Fed on Pastures Treated with Dieldrin, DDT, and Heptachlor1

Abstract

To determine the degree of milk contamination that might be expected when dairy cows were permitted to graze on an insectieide-treated pasture for varying lengths of time and at various intervals after treatment, a series of tests was initiated using dieldrin, DDT, and heptachlor applied at about twice the rate that might be considered normal dosage (0.5, 3, and 0.5 lb. per acre, respectively). When cows were permitted access to pastures immediately after treatment, the chemicals reached their maximum concentrations in the milk within 3 to 7 days (dieldrin 3 to 4 p.p.m.; DDT 7 to 8 p.p.m.; heptachlor as heptachlor epoxide 0.22 p.p.m.) and declined steadily thereafter.