New environmental and health concerns have hatched about an arsenic compound that's been added to chicken feed since the 1960s to produce healthier, happier, bigger-breasted birds.
A study by Duquesne University researchers has found that the organic arsenic added to chicken feed is chemically transformed into inorganic arsenic, a known carcinogen, much more quickly than previously thought.
Organic arsenic is added to the feed of some 70 percent of the 7 billion roasters grown annually in the United States. The inorganic arsenic is found in poultry waste, which is used as fertilizer.
That increases the risk that the inorganic arsenic will contaminate surface water and groundwater drinking supplies in farming areas where the chicken litter fertilizer is spread repeatedly, said John Stolz, professor of biology at Duquesne and co-author of the study reported in January in the peer-reviewed Environmental Science & Technology Online News.
"What goes into the ground is very different from the compound in the chicken feed," Mr. Stolz said. "That the organic arsenic transforms much faster means we could get a bolus of the stuff going through the groundwater aquifer."
Chicken producers in the United States use approximately 2.2 million pounds a year of a single arsenic feed additive, roxarsone, to control intestinal parasites, improve meat color, reduce stress and stimulate growth during the chickens' six-week life span. More than 95 percent of the additive is excreted unchanged in the chicken waste, which is regularly applied as fertilizer to surrounding farm fields.
It was previously thought that the inorganic arsenic formed slowly in the waste applied to fields, but the Duquesne study by Mr. Stolz and Duquesne environmental chemist Partha Basu found bacteria accelerated the conversion, which occurs in as little as a week.
Chronic exposure to inorganic arsenic is known to cause cancer and has been linked to heart disease, diabetes and declines in brain functions.
While arsenic occurs naturally in the environment, it is also a byproduct of coal-burning power plants and industries, some mining operations and copper smelting. The addition of arsenic to the environment by those industrial sources is closely scrutinized and controlled, and its use in pesticides and as a preservative in pressure-treated wood has been banned because of health concerns and the difficulty of removing it from the environment. And the U.S. Environmental Protection Agency is re-evaluating its approval of organic arsenic applications on golf courses to control weeds.
But its use in the meat industry has attracted attention only in recent years. One study discovered arsenic-laced fertilizer dust inside the homes of farm communities where the chicken litter-based fertilizer was applied. Because chicken production is geographically concentrated, the arsenic-contaminated waste creates a disposal problem and exposes more people to more arsenic.
Another study found arsenic in home garden fertilizer sold at lawn and garden stores, raising the risk that backyard gardeners will be exposed.
Mr. Stolz said he hoped his research, plus other recent reports about small amounts of the toxic arsenic showing up in the meat of chicken, will cause the U.S. Food and Drug Administration to reconsider its approval of the chicken feed additive.
"This paper won't convince the FDA, but the body of work out there may move it to act," Mr. Stolz said. "Some big U.S. companies raise chickens without using roxarsone and appear to manage."
The National Chicken Council, a Washington, D.C.-based trade organization for the industry, dismissed the Duquesne research as it has other studies.
"There's never been any showings of human health risks from the addition of small amounts of roxarsone to the feed," said Richard Lobb, a spokesman for the council.
The questions about arsenic's environmental and health effects have led some to stop using it. The European Union declared the use of roxarsone undesirable in 1999, and its member nations no longer use it.
Tyson Foods, the nation's second-biggest chicken producer, stopped using compounds containing arsenic in July 2004 after some negative publicity about roxarsone's use, not because the arsenic additive is an environmental or health risk.
"We believe roxarsone is safe; however, public criticism of the product in recent years led to public misunderstanding and prompted us to suspend using it," said Gary Mickelson, a Tyson spokesman. "We don't want there to be any question about the safety of the food we produce."
The biggest chicken farmer in Pennsylvania, Scott Sechler, doesn't add arsenic to feed, either, choosing 20 years ago to grow premium-priced chickens in Lebanon County without the use of antibiotics or growth enhancers.
"I'm selling a million birds a week and I feed them what I would want to eat," said Mr. Sechler, who markets the corn-and-soy-fed chickens under the Farmers Pride label and Bell & Evans, which is carried in Western Pennsylvania by Giant Eagle and Whole Foods.
He said most of the nation's chicken industry is under intense pressure to produce bigger birds faster, and to hold down prices, which has led other producers to use antibiotics and arsenic feed additives.
Ellen Silbergeld, of the Bloomberg School of Public Health at Johns Hopkins University, said the Stolz study showed that not only is the conversion of roxarsone into inorganic arsenic fast, it's efficient and quite likely a serious pathway for the introduction of a known carcinogen into the environment.
"I am concerned about the potential contamination of groundwater with inorganic arsenic [in Maryland] because we have a lot of poultry farms, and most people here get their drinking water from groundwater," Ms. Silbergeld said. Maryland produces 500 million broiler chickens a year, making it the 10th biggest chicken-producing state in the nation.
She said the FDA approved the use of roxarsone before enough was known about its environmental impacts. The FDA OK'd roxarsone in March 1944 and, by the mid-1960s, its use as a feed additive was widespread.
Mike Herndon, an FDA spokesman, said that, while the administration is aware of recent studies and environmental monitoring data by other government agencies, it "has no data to suggest that there have been any adverse health effects in humans" because of the roxarsone in chicken feed.
He said the Stolz study and others focused on environmental issues caused by roxarsone, not on the "residues in edible tissues," which is the FDA's regulatory responsibility. And the benefits of adding organic arsenic to chicken feed far outweigh the small increase in arsenic exposure to humans.
The EPA has set a limit on the amount of arsenic allowed in fertilizer applied to agricultural land, and Mr. Herndon said the arsenic levels in poultry litter from chickens fed roxarsone were under that limit.
In Pennsylvania, which produces about 150 million chickens a year, there are no regulations controlling the amount or type of arsenic in farm manure applications, according to the state Department of Agriculture.
Dale Kemery, an EPA spokesman, said the agency was not conducting its own research into roxarsone's effects on water supplies. "However, EPA is monitoring work being done at other agencies," he said, "and will consider the results of those studies for possible future action."
But Ms. Silbergeld said thinking "nobody's dead yet" and letting someone else do the testing is an inappropriate response by the chicken industry and government agencies charged with overseeing public health.
Don Hopey can be reached at firstname.lastname@example.org or 412-263-1983.