Polychlorinated Biphenyl Residues in Milk of Environmentally and Experimentally Contaminated Cows

Polychlorinated biphenyl (PCB) residues have been found in the milk of cows. In some instances the residue levels exceeded the FDA guideline 0.2 ppm in milk (equivalent to 5.0 ppm in milk, fat), and the milk was removed from the market. The major source of PCB residues in milk is Aroclor 1254 that has been used in coatings for concrete silos. Aroclor 1254 is unaltered in silos, and most of the contamination is adjacent to the walls (1, 2). We have observed a number of farms with PCB-treated silos and have fed Aroclor 1254 to cows under controlled conditions. This paper summarizes our major findings.