Residues of Heptachlor Epoxide and Telodrin in Milk from Cows Fed at Part per Billion Insecticide LeveIs

Residues of several chlorinated insecticides have been found to persist in the ppb range at harvest following normal control practices for insect pests of alfalfa and other forages. The studies reported herein were undertaken to determine the absence or presence in milk of two of these materials fed at such levels to dairy cows for extended periods of time. Technical heptachlor epoxide and Telodrin® (1,3,4,5,6,7,8,8- octachloro-l, 3,3a, 4, 7, 7a-hexahydro-4, 7-methanoisobenzofuran) were fed for 28 days to lactating dairy cows at levels of 5 and 20 ppb of their average daily roughage intake. Milk samples were taken at regular intervals before, during, and after insecticide feeding and analyzed for residues by gas chromatography. Small but measurable quantities of both insecticides were detectable in milk as early as 5 days after initiation of insecticide feeding and as late as 10 weeks after termination of feeding.