In fact, a 2004 study from the Institute for Agriculture and Trade Policy showed that more than half of store-bought and fast-food chickens contained elevated levels of arsenic. Roughly 2.2 million pounds of it are being used every year to produce 43 billion pounds of poultry. It's called roxarsone and it's used to fight parasites and increase growth in chickens.
New research not only confirms use of arsenic, but finds the addition of a frightening elixir of drugs that includes caffeine, banned antibiotics, and even Prozac. Researchers started off testing just for banned antibiotics but went ahead and looked for other substances because it didn’t add to the costof the test. What they found even surprised them, according to a story in The New York Times.
Prozac was added to feed because stressed out chickens produce tough meat and brutal conditions often mean a constantly nervous bird. Chickens are fed coffee pulp and green tea powder to keep them up longer so they eat more food, according to a story in The New York Times.