The Amount of DDT found in the Milk of Cows Following Spraying

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Abstract
This test was planned to show the effects of very heavy spraying with DDT and also the effects of the spraying schedule for hornfly control in this area. 17 animals of the Holstein and Jersey breeds were divided into 4 lots and sprayed with either 5% water sus-pensible powder or emulsion of DDT daily or with 0.25% water suspensible powder or emulsion semi-monthly. Two quarts of spray per animal per application were used in all cases. Spraying was started July 15 and discontinued Aug. 30. No precautions were taken to prevent the animals from obtaining DDT by licking themselves or other test animals. Milk samples were taken in the evening directly from the milking machine and DDT content detd. by the method of Schechter, et al. No DDT appeared in the milk collected the 3d and 10th days following the initial spraying, but it was present in all samples taken the 17th day. Maximum levels of DDT were reached in the milk of animals sprayed with emulsions sooner than with water-suspensible powder, but the ultimate maximum obtained from the 2 types of sprays was approx. the same (19 ppm.). The milk of one animal sprayed daily with 5% water-suspensible DDT attained a maximum of 33.6 ppm. The max. amount found in the milk of animals sprayed with Q.25% was 2.5 ppm. Appreciable quantities of DDT were present in the milk of 2 animals at the close of their lactation periods 119 and 126 days after the final spraying but none was found after calving 91 days later. Biological tests for toxicity of the milk to mice, flies (Musca domestica) and 3d instar mosquito larvae (Culex quinquifasciatus) and Aedes aegypti were negative.