In the absence of effective federal regulation, the meat industry uses hundreds of animal feed additives, including antibiotics, tranquilizers, pesticides, animal drugs, artificial flavors, industrial wastes, and growth-promoting hormones, with little or no concern about the carcinogenic and other toxic effects of dietary residues of these additives. Illustratively, after decades of misleading assurances of the safety of diethylstilbestrol (DES) and its use as a growth-promoting animal-feed additive, the United States finally banned its use in 1979 some 40 years after it was first shown to be carcinogenic. The meat industry then promptly switched to other carcinogenic additives, particularly the natural sex hormones estradiol, progesterone, and testosterone, which are implanted in the ears of more than 90 percent of commercially raised feedlot cattle. Unlike the synthetic DES, residues of which can be monitored and use of which was conditional on a seven-day preslaughter withdrawal period, residues of natural hormones are not detectable, since they cannot be practically differentiated from the same hormones produced by the body. The relationship between recently increasing cancer rates and the lifetime exposure of the U.S. population to dietary residues of these and other unlabeled carcinogenic feed additives is a matter of critical public health concern.
