In 2008, Mexico refused a shipment of U.S. beef. The meat exceeded Mexico's regulatory upper limit for copper. The meat was returned to the United States -- where it was sold and eaten.
Contamination of meat by heavy metals, veterinary drugs and pesticides is a problem which the U.S. government has for the most part ignored. And while bacterial contaminants can be killed by cooking, chemical residues stay in the meat.
“Sick dairy cows are given medications to help them recover, but if it appears an animal will die, it's often sold to a slaughterhouse as quickly as possible, in time to kill it before it dies.”