A ten‐year study of chlorinated hydrocarbon insecticide residues in bovine milk in Illinois, 1972–1981

Abstract
Milk supplies in Illinois were monitored for chlorinated hydrocarbon insecticide residues from 1972 through 1981. The percentage of milk samples that were contaminated with aldrin/ dieldrin, DDT and its analogs, and BHC/lindane decreased during the 10‐year sampling period. The percentage of samples contaminated with aldrin/dieldrin decreased from 98.7% in 1978 to 5.9% in 1981. The amount of aldrin/dieldrin residues found in contaminated samples also decreased from an average of 0.077 ppm (1972–79) to 0.001 ppm in 1980–81. The levels of chlordane and heptachlor/heptachlor epoxide residues in milk did not decrease, but residues of BHC and DDT decreased gradually over the 10‐year period. The percentage of samples that had less than 0.1 ppm of all chlorinated hydrocarbon residues combined ranged from 10.6% to 25.7% during 1972 through 1978 and increased to 36.2% in 1979, 71.1% in 1980, and 61.4% in 1981.