http://pubs.acs.org/cen/government/85/8515gov2.html
Arsenic In Chicken Production

A common feed additive adds arsenic to human food and endangers water
supplies
Bette Hileman

FOR ENVIRONMENTALISTS and some public health experts, one of the most
puzzling practices of modern agriculture is the addition of
arsenic-based compounds to most chicken feed. The point of the
practice is to promote growth, kill parasites that cause diarrhea, and
improve pigmentation of chicken meat. But Tyson Foods, the U.S.'s
largest poultry producer, stopped using arsenic compounds in 2004, and
many high-end and organic growers raise chickens quite successfully
without them. What's more, McDonald's has asked its suppliers not to
use arsenic additives, and the European Union banned them in 1999.


Stephen Ausmus/USDA
Roxarsone€”4-hydroxy-3-nitrobenzenearsonic acid€”is by far the most
common arsenic-based additive used in chicken feed. It is mixed in the
diet of about 70% of the 9 billion broiler chickens produced annually
in the U.S. In its original organic form, roxarsone is relatively
benign. It is less toxic than the inorganic forms of arsenic-arsenite
[As(III)] and arsenate [As(V)]. However, some of the 2.2 million lb of
roxarsone mixed in the nation's chicken feed each year converts into
inorganic arsenic within the bird, and the rest is transformed into
inorganic forms after the bird excretes it.

According to the Environmental Protection Agency, long-term exposure
to inorganic arsenic can cause bladder, lung, skin, kidney, and colon
cancer, as well as deleterious immunological, neurological, and
endocrine effects. Low-level exposures can lead to partial paralysis
and diabetes. "None of this was known in the 1950s when arsenicals
were first approved for use in poultry," says Ellen K. Silbergeld, a
toxicologist at Johns Hopkins University Bloomberg School of Public
Health.

Three different pathways exist by which roxarsone in chicken feed can
contribute to human arsenic exposure. Roxarsone, or its breakdown
products, ends up in chicken meat and adds to the dietary intake of
arsenic; roxarsone excreted in chicken litter contaminates land and
groundwater after the manure is spread on cropland; and the large
amounts of poultry litter made into fertilizer pellets for home
gardens and lawns contaminate homegrown produce with arsenic and
expose the consumer to arsenic dust.

Last year, a team led by James A. Field of the department of chemical
and environmental engineering at the University of Arizona reported
that under anaerobic conditions, roxarsone is converted to inorganic
arsenic within eight months after poultry litter is spread on fields
(Environ. Sci. Technol. 2006, 40, 2951). "Roxarsone is not very
toxic," Field says, "but in anaerobic environments, it is transformed
into highly toxic forms."

In January, Partha Basu, associate professor of chemistry and
biochemistry at Duquesne University and colleagues reported that
microorganisms of the genus Clostridium in chicken litter rapidly
transform roxarsone into inorganic arsenate under anaerobic conditions
(Environ. Sci. Technol. 2007, 41, 818). "We see As(V) created in less
than 10 days," Basu says, noting it "can be readily leached into
groundwater."

Chicken manure introduces huge quantities of arsenic to agricultural
fields. According to Donald L. Sparks, professor of marine studies at
the University of Delaware, poultry litter is spread on land at the
rate of 9 to 20 metric tons per hectare. Each year, he estimates, 20
to 50 metric tons of roxarsone in chicken litter is applied to fields
on the Delmarva Peninsula, a region that includes parts of Delaware,
Maryland, and Virginia.

A group led by Johns Hopkins' Silbergeld analyzed arsenic in tap water
on the Delmarva Peninsula. It found higher levels of arsenic in areas
where chicken litter is spread on fields and lower levels in areas
where chicken manure is not spread. The research was reported at the
Society of Toxicology meeting in late March.

One reason for the increasing concern about roxarsone is that the
weight of evidence for arsenic as a carcinogen is much greater now
than it was a decade ago. In 2001, EPA proposed reducing the maximum
contaminant levels for arsenic in drinking water from 50 ppb to 10 ppb
and required water systems to comply by January 2006. The agency took
this action in response to three National Research Council reports
that concluded the standard of 50 ppb posed unreasonable risks. And
even the new lower maximum appears problematic. According to EPA
estimates, the risk of cancer from 10 ppb of arsenic in tap water is 1
in 2,000, a 50-fold higher risk than that allowed for most other
carcinogens.

Even though the drinking water standard for arsenic has been
strengthened, the standards for arsenic residues in poultry-2,000 ppb
for liver and 500 ppb for muscle-have remained unchanged for decades.
Furthermore, neither the Food & Drug Administration nor the Department
of Agriculture has actually measured the level of arsenic in the
poultry meat that most people consume. USDA has measured it only in
chicken livers.

In 2004, Tamar Lasky, an epidemiologist then at USDA's Food Safety &
Inspection Service, estimated intake of arsenic from chicken
consumption. To do this, she used liver measurements and a technical
bulletin published by the roxarsone producer Alpharma. She concluded
that the mean concentration in young chickens is 390 ppb, which is
three to four times greater than arsenic levels in other types of
poultry and meat from other animals.

Lasky also calculated that people ingest a mean of 1.3 to 5.2 ??g per
day of inorganic arsenic from chicken alone. Those who eat much more
chicken than average may ingest 21 to 31 ??g of inorganic arsenic per
day, she wrote, which for some is greater than the tolerable daily
intake recommended by the World Health Organization. Because per
capita chicken consumption has more than doubled since the 1960s, it
may be necessary to review the assumptions regarding the overall
arsenic intake, Lasky observed.

THE ONLY PERSON who actually has obtained data on the arsenic content
of chicken meat, other than livers, is David Wallinga, a physician and
director of the food and health program at the Institute for
Agriculture & Trade Policy. IATP, which is a research and advocacy
organization in Minneapolis, tested raw chicken from Minnesota and
California supermarkets.

Fifty-five percent of the 151 samples of raw chicken in these tests
contained detectable arsenic ranging from 1.6 to 21.2 ppb, Wallinga
wrote in a report. Nearly three-quarters of the samples from
conventional producers had detectable levels of arsenic, but only
one-third of samples from certified organic and other premium chicken
suppliers had detectable levels. On the other hand, no arsenic was
found in samples from Tyson and Foster Farms, which have both stopped
using roxarsone. "As a physician, I find it ludicrous that we continue
feeding arsenic to chickens now that we know it increases our cancer
risk, and it's unnecessary for raising chickens," Wallinga says.

According to the Washington, D.C.-based National Chicken Council,
Wallinga's report is not scientific and means very little. "There is
no reason to believe that there are any human health hazards from this
type of use" of arsenic-bearing feed additives, the council says.
FDA's Center for Veterinary Medicine declined an opportunity for an
interview about roxarsone.

Banning roxarsone in chicken feed would not eliminate all arsenic from
chickens or the environment. Some poultry consume water from wells
contaminated with natural arsenic. Some are raised on soil
contaminated from heavy use of arsenical pesticides in past cotton
cultivation. Arsenic also is released from coal-fired power plants.
But banning the additive in feed would eliminate a substantial portion
of arsenic from the human food chain and some of the arsenic in
drinking water.

Even if regulators don't act, roxarsone may be on its way out because
of lack of demand. There are reports that Bon Appétit Management Co.,
a $400 million food service company, may soon join McDonald's and
Tyson Foods in prohibiting poultry suppliers from using the additive.