Researchers at Johns Hopkins University said they found levels of arsenic in chicken that exceeded amounts that occur naturally, and warned that they could lead to a small increase in the risk of cancer for consumers over a lifetime.
The levels were well below danger levels set in US federal safety standards, although the researchers said that those were established in the 1940s. And the chicken samples tested were from 2010 and 2011, before sales of the drug that researchers say was a major driver of the elevated arsenic levels, roxarsone, were suspended.
A spokeswoman for the chicken industry said the levels found by researchers were low, but the researchers said that the elevated levels are important because the US Food and Drug Administration (FDA) has not banned the drug, and it is still being sold abroad.
The issue of arsenic in food has drawn attention since research last year by Consumer Reports found substantial arsenic levels in rice.
Keeve Nachman, a scientist at the Johns Hopkins Center for a Livable Future and the chicken study’s main author, acknowledged that the levels of inorganic arsenic in chicken were far lower than those found in rice but said that any deliberate additive amounted to a public health risk.
Roxarsone, and a chemically similar drug, nitarsone, remain the last federally approved uses of arsenic in food production, he said.
Roxarsone, known by its brand name 3-Nitro, kills intestinal parasites, promotes growth and makes meat look pinker. It contains organic arsenic, which is far less toxic than its inorganic counterpart.
For decades, it was believed that animals simply excreted organic arsenic.
However, evidence is emerging that it might also be converted into its carcinogenic cousin in the body of the chicken.
The study, which measured inorganic arsenic levels in chicken, found roxarsone in about half the samples. The researchers said they tested samples that were gathered from December 2010 to June 2011 — before the sales of roxarsone were suspended — because they wanted to examine whether the drug led to increased levels of inorganic arsenic.
A spokeswoman for the company that sells the drug, Zoetis, said sales in the US “remain suspended pending the ongoing evaluation of relevant scientific data regarding the use of this product in poultry.”
She said that the company no longer manufactures the drug and that it is selling down remaining stock in markets that still permit it, all of them in Latin America.
A spokesman for the FDA said in an e-mail that the company “has assured FDA that it will not begin marketing the drug again in the United States without first consulting with the agency.”
The study, set to be published yesterday in the Environmental Health Perspectives journal, tested 140 samples of chicken from grocery stores in 10 US cities.
It found that chicken contained inorganic arsenic at the level of about 2 parts per billion. Organic chicken was also tested. It contained about half a part per billion.
US federal standards allow anything below 500 parts per billion of total arsenic.
The study estimated that the exposure could cause an additional 124 deaths in the country annually from lung and bladder cancer, if the drug were fed to all chickens.
The US National Chicken Council said the findings reflected “very low levels of arsenic” and were not worrisome.