You might associate arsenic with the 1944 who-done-it film Arsenic and Old Lace, in which affluent elderly gentlemen are poisoned by sweet old ladies. Coincidentally, the same year the film was released, the US Food and Drug Administration (FDA) approved the use of the drug 3-nitro-4-hydroxyphenylarsonic acid (Roxarsone) as an animal feed additive. At that time animal drugs containing arsenic were routinely used in animal feed for chickens, turkeys and pigs (but were most commonly used in broiler chickens). In poultry, they were used for growth promotion, feed efficiency and improved pigmentation; they were also approved in combination with other drugs to prevent coccidiosis. Roxarsone was used in poultry feed to kill parasites and promote growth.

In 2011, an FDA study found that chickens that had eaten Roxarsone had higher levels of arsenic in their livers than chickens that had not eaten it (FDA, 2015). Due to technical difficulties, the FDA did not test any other part of the chickens’ bodies. However, a more recent study found a range of arsenic species (compounds containing arsenic) in the breast meat of chickens fed Roxarsone (Liu et al., 2016).

Following publication of the FDA study, Pfizer Inc voluntarily suspended sale of Roxarsone. Had they not stopped sales, the FDA probably would have banned the product since arsenic is a known carcinogen. In 2015, the FDA withdrew approval of using Roxarsone in animal feeds. It is banned in the European Union; however, it continues to be legally used in many other countries where its presence in chicken manure significantly enhances the uptake of arsenic species by vegetables (Huang et al., 2014; Yao et al., 2013).  

This is just one of the better-known examples of the many different chemicals that factory-farmed animals have been force-fed up until slaughter in recent years.