Here is another recent article on this topic from the Chemical and
Engineering News. Since arsenic isn't really necessary in chicken feed
and since it is definitely polluting the ground water and may be causing
human health concerns, it seems reasonable to want it out of our food.
It's been banned in the EU since 1999 IIRC.
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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 µg per day
of inorganic arsenic from chicken alone. Those who eat much more chicken
than average may ingest 21 to 31 µg 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.