The pharmaceutical giant Pfizer will voluntarily suspend US sales of a poultry-pumping additive after studies showed it can leave traces of arsenic in chicken livers, the US government said on Wednesday.
The Food and Drug Administration said the move followed a recent study of 100 broiler chickens which found that those treated with the animal drug 3-Nitro, or Roxarsone, had higher levels of inorganic arsenic in their livers than untreated chickens.
The levels detected were "very low" and do not pose a health risk, the FDA said.
The drug is marketed by Alpharma, a subsidiary of Pfizer, and has been used since the 1940s to ward off infection, make chicken skins more yellow and boost the birds' growth.
"FDA detected increased levels of inorganic arsenic in the livers of chickens treated with 3-Nitro, raising concerns of a very low but completely avoidable exposure to a carcinogen," said Michael Taylor, FDA deputy commissioner for foods.
"We are pleased to announce that the company is cooperating with us to protect the public health."
The order will take effect in 30 days.
The FDA approved 3-Nitro in 1944, when it became the first arsenic-containing new animal drug product approved by the US regulatory agency.
It is fed mainly to chickens but is also used for swine and turkeys. Most of its sales are in the United States, though US regulators said they would share their findings with international governments.
Arsenic-based food additives are banned in Europe, according to an industry newsletter published by the Netherlands-based Worldpoultry.net.
Perdue, a major chicken producer in the United States, said it has not used Roxarsone in several years and saw no decline in flocks' health.
"Perdue does not use Roxarsone or arsenic. We phased out the use of this animal health feed additive in April 2007 as we improved our flock health and management programs," spokesman Joe Forsthoffer said in an email to AFP.
"We've found that, through improved flock health programs and housing environments, we are able to produce healthy chickens without it."
Pfizer and Alpharma representatives could not immediately be reached for comment.
The National Chicken Council, which said it represents 95 percent of chicken producers and processors in the United States, issued a statement saying that consumers need not change their buying or eating habits.
"3-Nitro has been used to maintain good health in chicken flocks for many years. It is used in many, but not all, flocks," the council statement said.
"Consumers can continue to buy and eat chicken as they always have."
Some poultry farmers use 3-Nitro to ward off coccidiosis, a parasitic disease that attacks an animal's intestines. It also helps chickens gain weight and gives a golden color to their skin.
Alpharma said on its website that Roxarsone is a "non-antibiotic feed additive that helps increase the rate of weight gain and improve feed efficiency of pigs by promoting a healthy gut."
The arsenic in Roxarsone is organic, according to Alpharma.
However the chickens were found to have inorganic arsenic, the poisonous kind, in their organs, according to FDA research.
The study of toxicity in chicken livers began after researchers showed that organic arsenic could change form.
"Published scientific reports have indicated that organic arsenic, a less toxic form of arsenic and the form present in 3-Nitro, could transform into inorganic arsenic," the FDA statement said.
A coalition of consumer groups filed a federal lawsuit last month against the FDA over the use of human antibiotics in animal feed, saying it creates dangerous superbugs.
The suit alleges that the regulatory agency concluded in 1977 that the practice of feeding healthy animals low doses of penicillin and tetracycline could lead to the rise of antibiotic-resistant bacteria in people, but continues to allow it anyway.
Roxarsone was not included in the suit because it is not an antibiotic.
Explore further: High-dose opioid prescribing continues to climb