Most chicken eaten in the United States contains three to four times as much arsenic as do other kinds of meat and poultry. That finding may require researchers to revise upward their estimates of how much of this toxic metal people consume in food, but the revised amount still doesn’t exceed what’s accepted as safe.
Inorganic arsenic is a carcinogen; organic forms–compounds containing carbon and arsenic–are less toxic and combat animal diseases and accelerate growth. Therefore, organic arsenic is an approved ingredient in roxarsone, a feed additive used in poultry and swine. About 70 percent of chickens grown for meat receive roxarsone. They excrete most of the arsenic but retain some in their tissues, particularly the liver, in both organic and inorganic forms.
To ascertain how much arsenic remains in slaughtered animals, Tamar Lasky and her U.S. Department of Agriculture colleagues in Washington, D.C., analyzed USDA data on arsenic concentrations in the livers of more than 5,000 chickens, 2,700 turkeys, 5,500 pigs, and 7,000 cattle, sheep, and other animals.
The average concentration of arsenic in livers from young chickens–from which most chicken meat is derived–was 0.39 parts per million (ppm). Liver-arsenic concentrations for mature chickens, turkeys, and pigs ranged from 0.10 to 0.16 ppm, and those for all other species contained about 0.10 ppm.
The researchers then extrapolated how much toxic arsenic might be consumed in chicken meat. They used past estimates of the ratios of liver arsenic to muscle arsenic, and inorganic to organic arsenic in chickens and then factored in how much chicken U.S. consumers eat.
A typical adult may ingest 3.62 to 5.24 micrograms of inorganic arsenic per day from chicken alone, Lasky–who’s now at the National Institutes of Health in Bethesda, Md.–and her colleagues report in an upcoming Environmental Health Perspectives.
Among the 1 percent of the U.S. population eating the most chicken, each person may ingest between 21.13 and 30.59 micrograms of inorganic arsenic daily, the researchers figure. Even that dose of inorganic arsenic doesn’t exceed the World Health Organization’s suggested limit for intake of 2 milligrams per kilogram of body weight per day, but it does represent a “sizable portion of the tolerable daily intake,” the researchers say. Tainted drinking water is generally considered the greatest source of arsenic in people.
“It didn’t alarm me,” says Timothy N. Chamblee of Mississippi State University, after seeing the new study. The estimated average exposure “is not an amount that’s excessively high,” he says.
“Even though it’s organic arsenic being fed to these chickens, [they contain] a lot more inorganic arsenic at the end of the day,” says John F. Stolz, a microbiologist at Duquesne University in Pittsburgh. That fact is “screaming for research” into how the body processes arsenic, he says.
Apart from any physiological effects on chickens themselves or consumers, feed additives introduce tons of organic arsenic into the environment every year, says Stolz. Some of that arsenic is converted into inorganic forms, which could contaminate water supplies, he notes.
Correction: Because of an error in the referenced research article, this article overstated the tolerable intake of inorganic arsenic. A United Nations committee recommends consumption of no more than 15 micrograms per kilogram of body weight per week.
