Arsenic is a known human carcinogen—not something you would knowingly bring home from the grocery store on a regular basis. But it's on the menu every time you buy nonorganic chicken, according to a first-of-its-kind study published in the journal Environmental Health Perspectives.
Keeve Nachman, PhD, director of the Farming for the Future Program at Johns Hopkins School of Public Health, and his coauthors analyzed 78 samples of chicken purchased from grocery stores across the country to determine how much arsenic each sample contained. It's widely known that chicken producers add arsenic-based drugs to chicken feed to speed the birds' growth and treat certain infections, but no one, not even the Food and Drug Administration (FDA), which approved those drugs, has ever analyzed meat to see if that carcinogenic arsenic was winding up on your dinner plate. "The FDA has even said that any animal drug that increases concentrations of inorganic arsenic (the dangerous form of the metal linked to cancer) is of concern," Nachman says.
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So he wanted to find out how much inorganic arsenic really was winding up in meat.
Forty of the purchased samples were conventional chicken, 13 were labeled "antibiotic free," and 25 were certified organic. The conventional chicken contained the highest levels of inorganic arsenic at an average of 1.8 parts per billion (ppb), compared to 0.7 ppb in the chicken labeled antibiotic free and 0.6 ppb in the certified-organic sample.
Most of the inorganic arsenic in chicken comes from an arsenic-based drug called roxarsone, which is added to chicken feed as a growth promoter and as an antimicrobial, although some arsenic exists in drinking water. Nachman writes in the study, however, that "such exposures are unlikely to be fully responsible for the differences we observed between different types of samples, as the rate of addition of roxarsone to animal feed is between 22.7 and 45.5 ppm (parts per million)."
Technically, the Food and Drug Administration (FDA) requires chickens to be fed a roxarsone-free diet for five days before slaughter to allow any residues of the drug to pass through chickens' systems. But Nachman's study found that that isn't working. The researchers detected roxarsone in half of the conventional chicken tested and in one of the "antibiotic-free" chicken samples.
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That's concerning, he says, because of what may be happening when you cook your chicken. In their study, he and his coauthors found that arsenic levels went up by nearly a third after the chicken was cooked, suggesting that either inorganic arsenic becomes concentrated as water evaporates or that residual residues of roxarsone—or its metabolites—break down into inorganic arsenic during cooking. "We're not sure exactly what's happening here," says Nachman, "but we do know that cooking makes it worse."
While the Environmental Protection Agency has set a limit of 10 ppb for arsenic in drinking water, the FDA has never set similar standards for arsenic in food, despite a growing number of reports that the heavy metal is winding up in rice, apple juice, and even beer. However, the agency has issued statements in the past saying that levels of arsenic in chicken should not exceed 1 ppb. Seventy percent of the conventional chicken samples in this study exceeded the 1ppb limit, says Nachman.
And yet, the agency refuses to ban arsenic-based drugs. In 2011, Pfizer, the U.S. manufacturer of roxarsone, "suspended" sales of the drug (the company didn't say it would stop them forever). The drug was never banned by the FDA and is still widely used in other countries. And, says Nachman, "FDA still has a number of approved animal drug products that contain arsenic." One of those is nitarsone, an arsenic-based drug favored by U.S. chicken producers that has a chemical structure that's very similar to roxarsone's.
So what's all this doing to you?
For the last part of his study, Nachman calculated the risk of lung and bladder cancers—the two types most strongly associated with ingesting arsenic—from eating conventional chicken. Based on EPA's calculations, arsenic you're exposed to from water and other naturally occurring sources leads to approximately 4.0 cases of cancer in 100,000 people each year. The levels of arsenic in chicken would add an additional 3.7 cases to that, nearly doubling the rates of lung and bladder cancers among people who eat chicken on a daily basis.
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It could even be leading to more arsenic in the food supply as a whole. Rice farmers in Arkansas have filed a lawsuit against Pfizer and Tyson Foods over alleged contamination of their rice fields with arsenic. Rice grown in Arkansas has some of the highest arsenic levels of domestically grown rice, and the farmers are pointing the finger at Tyson chicken producers, who sold the farmers chicken litter to fertilize their rice paddies.
How to keep arsenic out of your kitchen:
• Buy organic. Roxarsone and other arsenic-based feed additives are banned in certified-organic chicken production.
• Opt for "antibiotic free" if you can't find organic. Although antibiotic-free claims aren't independently verified and don't necessarily mean that a product is free of arsenic (arsenic acts like an antibiotic, but the FDA doesn't consider it one), Nachman' team found low levels of arsenic in those products. "If you look at organic, 'antibiotic-free,' and chicken from producers with policies against using arsenic, they were all below that FDA safety limit," he says.
• Buy local. Talking to the people who raise your poultry is the best way to know what is—and isn't—in it. Check out your favorite farmer's market to find local producers.
Published on: May 14, 2013
Updated on: May 15, 2013