Study Finds an Increase in Arsenic Levels in Chicken

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 federal safety standards, though the researchers pointed out that those were first 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 contend that the elevated levels are important because the Food and Drug Administration has not banned the drug, and it is still being sold abroad.

The issue of arsenic in food has drawn public attention since research last year by Consumer Reports found substantial arsenic levels in rice. Arsenic residue in rice often comes from water used in farming.

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. But evidence is emerging that it may 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 meat samples that were gathered from December 2010 to June 2011 — before the sale of roxarsone was 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 United States “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 F.D.A. 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, to be published on Saturday in the journal Environmental Health Perspectives, tested 140 samples of chicken from grocery stores in 10 American cities. It found that chicken contained inorganic arsenic at the level of about two parts per billion. Organic chicken was also tested. It contained about half a part per billion. 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 National Chicken Council said the findings reflected “very low levels of arsenic,” and were not worrisome.

“These samples, taken as part of this extremely small, agenda-driven study, were purchased before roxarsone was removed from the market in June 2011, and the conclusions are used to intentionally mislead consumers,” said Ashley Peterson, vice president of scientific and regulatory affairs at the National Chicken Council.

Sale of the drug was suspended in 2011 after the F.D.A. released a report finding inorganic arsenic in chicken livers, but the agency did not ban roxarsone. In that report, the agency said, “any new animal drug that contributes to the overall inorganic arsenic burden is of potential concern.” Consumer advocates contended the drug should be banned.

Chicken consumption in the United States has nearly tripled since the 1960s, increasing human exposure. Each American ate about 83 pounds of chicken in 2011, compared with about 30 pounds per person in 1965, according to the National Chicken Council.

Dr. Nachman said that Zoetis currently sells a similar arsenic-based drug, nitarsone, which is approved for use in chickens and turkeys. The company’s spokeswoman, Elinore White, said nitarsone was not a substitute for roxarsone, and that scientific data supported its safety.

The F.D.A. spokesman said 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.”