A study published online recently in the journal Environmental Health Perspectives documented slightly elevated levels of arsenic in samples of chicken purchased at grocery stores in 10 cities in the U.S.
So how did trace amounts of this toxin end up in supermarket poultry?
Well, arsenic-based drugs are approved for use in chicken and turkey production. At the time of the grocery-store testing, back in late 2010 and early 2011, a drug called Roxarsone was still being used in chicken feed to stave off infections with parasites. (The drug was voluntarily pulled from the market in June 2011 by its manufacturer.)
"We did the study to learn whether using arsenic-based drugs leads to increases in the toxic form of arsenic in meat," explains researcher Keeve Nachman of Johns Hopkins. And it turns out, it does. A little.
The researchers documented 2.3 ppb that's parts per billion of inorganic arsenic (the more toxic type of arsenic) in the meat of chicken that had measurable levels of Roxarsone.
By comparison, the meat from chicken that had no detectable levels of Roxarsone had 0.8 ppb of inorganic arsenic. That's three times less.
But it's important to point out that these low levels are far below the 500 ppb tolerance levels set by the FDA.
The researchers found no measurable trace of the arsenic-based drug in the 25 organic samples they tested (Roxarsone is not allow in organic chicken). By comparison, 20 of the 40 samples of meat from chickens raised conventionally did contain the drug.
The National Chicken Council released a statement calling the study's conclusions misleading. Chicken producers, the council says, are no longer using any arsenic-based drugs.
In lieu of Roxarsone, which had been used to prevent intestinal parasites, chicken producers have switched to drugs known as ionophores.
"Today, folks [chicken producers] are just doing the best they can without" Roxarsone, says Tom Super of the National Chicken Council. He says the ionophores are not as effective against the parasites.
The FDA, in this Q & A, says another arsenic-based drug known as Nitarsone is still being marketed. It's approved for use in chickens and turkeys. Though the FDA does not disclose animal drug sales data, the drug is used to prevent outbreaks of blackhead, an infection caused by parasites, in turkeys.
The National Turkey Federation says Nitarsone is used primarily in the turkeys' first few weeks of life and used more heavily during the summer months, when blackhead is more likely to occur. The industry depends on the drug as a preventive, since there's no effective treatment once an outbreak occurs.
The authors of the new study say they hope the FDA considers their conclusions in making decisions about the approvals for these drugs.
"Roxarsone still continues to be sold by [drug company] Zoetis in Latin America" and is still approved for use here, Johns Hopkins' Nachman says, despite the fact that it was voluntarily pulled from the market in 2011.
The FDA says it continues to investigate all uses of arsenic-based drugs in food-producing animals, and agency spokesperson Jalil Isa says the agency "will take the appropriate action to protect public health."