Chicken, Now Available with Less Poison

By Michael Crupain, MD, MPH

(Note:  This Article was originally published in the American College of Preventive Medicine Resident Physician Newsletter)

Many people would probably be surprised to find out that arsenic, the metalloid element sometimes referred to as “the king of poisons”, has been a common additive to chicken feed for over 60 years.  Organic arsenic is the active component in Roxarsone, a drug that is fed to birds in order to speed growth, kill parasites, and improve the cosmetic appearance of their meat.  It is estimated that about 2 million pounds of Roxarsone are fed to conventionally raised chickens each year and according to one industry representative 88% of all chickens receive the drug. 

As of July 8, 2011, however, Pfizer the maker of Roxarsone, has voluntarily suspended sales of the drug.   This moves comes on the heels of an FDA study in which increased levels of inorganic arsenic were detected in the livers of chickens fed Roxarsone.

While chickens are fed Roxarsone, an organic form of arsenic, recent studies have suggested that the arsenic can be converted to the toxic inorganic form, by bacteria present inside a chicken’s gastrointestinal tract and in chicken manure.

Inorganic arsenic is classified as carcinogenic to humans, and chronic, low level exposures are associated with medical complications including damage to cells and chromosomes, which can lead to skin, bladder, liver, and lung cancers as well as conditions such as heart disease, stroke, peripheral vascular disease, anemia, diabetes mellitus, and peripheral neuropathy. New data also suggests that arsenic may be an endocrine disruptor.

The United States Food and Drug Administration originally approved Roxarsone for use in animals in 1944.  The FDA risk assessments on the safety of arsenic containing drugs was done over half-a-century ago with data supplied by the industry about residue levels in meat and the estimated average per-capita chicken consumption at that time.   Since then, however, the amount of chicken consumed in the United States has increased dramatically.  While in 1960’s the average American ate approximately 28lbs of chicken per year, by the year 2010 the average annual per capita consumption had tripled to almost 90lbs.  This means that consumers are likely being exposed to significantly higher levels of arsenic than would have been considered during the original studies assessment conducted by FDA.    Industry trade groups have repeatedly asserted that studies that have examined arsenic residues in chicken have found the levels to be less than the permissible tolerances set by the FDA.  Despite this, these tolerances were set in the 1950s, without the benefit of the public health research community’s current understanding of arsenic’s carcinogenic effects and potential to induce other adverse health outcomes.    In addition, chicken waste containing arsenic can contaminate the water that people drink as well as the meat of other food animals and potting soil mixtures.

Surprisingly, arsenic-containing feeds have been shown not to be cost effective to industry.  In a recent study published in the Journal of Applied Poultry Research, investigators found that chickens fed a diet without arsenic or other growth promoting antimicrobials were statistically indistinguishable from chickens that were fed arsenic and other antimicrobials (the researchers actually saw a trend for increased production indices in the chickens not fed the drugs).  Under pressure from public health advocates, both Foster Farms and Perdue, two of the countries biggest chicken producers, have both claimed to stop using arsenic containing drugs in their chicken feeds and these drugs have never been approved for use in the EU and should not used in organically grown chickens. 

It is noteworthy that while sales of Roxarsone have been voluntarily suspended by its domestic manufacturer, the FDA has not withdrawn its approval of the drug.  According to the New York Times, Pfizer plans to do full scientific assessment of the drug before it tries to return it to the market.

”While a voluntary cessation of sale of arsenical drugs may sound like a step in the right direction, FDA should do its job and withdraw the approval for Roxarsone,” says Dr. Keeve Nachman of the Johns Hopkins Center for a Livable Future.  “Allowing Pfizer to self-police sets a bad precedent with regard to how FDA handles legitimate public health concerns associated with drugs used in food animal production.”