Researchers from Johns Hopkins University have made some discoveries about chicken that might make you reconsider how much of it you want to eat.

According to a study published yesterday in the journal Environmental Health Perspectives, chicken was shown to have higher levels of arsenic than those that occur naturally, which could lead to an increase in the risk of cancer, The New York Times reported.

The study tested 140 samples of chicken between December 2010 and June 2011 from grocery stores in ten American cities. The researchers found inorganic arsenic levels at two parts per billion in conventially raised chicken. In organic chicken, inorganic arsenic levels were lower at about half a part per billion. Federal standards allow a total of 500 parts per billion for chicken.

Although the levels were well below U.S. Food and Drug Administration (FDA) standards, researchers stress that the higher levels are noteworthy since chickens were fed roxarsone, a weight-gain drug for livestock, which was found in about half of the samples. Pfizer, the drug's manufacturer, voluntarily suspended the sale of roxarsone in the U.S. in June 2011 over concerns of unnecessary carcinogen exposure.

Roxarsone, also known as 3-Nitro, kills intestinal parasites, promotes growth, and makes meat appear pinker. The researchers purposefully used meat samples from before the suspension of roxarsone to test whether the drug increased levels of inorganic arsenic. Although the drug contains organic arsenic, which is much less toxic, there is evidence that it could be converted into the carcinogenic form within the body of the chicken, according to The New York Times.

Keeve Nachman, the study's main author and a scientist at the Johns Hopkins Center for a Livable Future, said that any deliberate additive amounted to a public health risk. Zoetis, the Pfizer subsidiary that sells roxarsone, also distributes a chemically similar drug, nitarsone, which is used in chickens and turkeys. Elinore White, a spokeswoman for Zoetis told The New York Times that nitarsone is not a substitute for roxarsone and that scientific data supported its safety.

Still, inorganic arsenic has been associated with an increased risk of nonmelanoma skin cancer, as well as bladder, liver, and lung cancer, according to the U.S. Environmental Protection Agency. The study suggests that if roxarsone were fed to all chickens, it would cause 124 more deaths annually from lung and bladder cancer.

An FDA spokesman told The New York Times that the agency "continues to investigate all uses of arsenic-based drugs in food-producing animals and will take the appropriate action to protect public health."


Nachman KE, Baron PA, Raber G, Francesconi KA, Navas-Acien A, Love DC. Roxarsone, Inorganic Arsenic, and Other Arsenic Species in Chicken: A U.S.-Based Market Basket Sample. Environmental Health Perspectives. May 2013; 10. Accessed May 12, 2013.

Tavernise S. "Study Finds an Increase in Arsenic Levels in Chicken." The New York Times. Accessed May 12, 2013.