The arsenic compound roxarsone, which is frequently added to chicken feed to fight parasites and increase growth, is a Class A carcinogen linked to heart disease, diabetes and declines in brain function, according to a report in The Washington Post.

Though the industry has been using roxarsone since its approval by the Food and Drug Administration in 1944, it seems to have little effect except raising the blood count. The meat, thus pinker, appeals more to the customer.

Similarly, the arsenic additive fuels angiogenesis in human cells, which might lead to cancer. Chicken growers have also reported illness from contact with roxarsone while preparing feed. EU outlawed the use of arsenic in chicken feed in 1999. Though several producers like Tyson Foods and Perdue Farms have responded, more than 70% of over 9 billion broiler chicken produced annually in the U.S. are fed roxarsone.