arsenic: Food for Chickens - Poison for Man

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Food for Chickens, Poison for Man

A widespread farming practice is adding arsenic to the food chain.

By Melinda Wenner, posted September 20th, 2006.

http://scienceline.org/2006/09/20/env-wenner-arsenic/

When Gwen raised broiler chickens for Pilgrim’s Pride from 2001 to

2004, she had to use poultry feed provided by the company. After a few

incidents when she felt physically ill working with it—“I would start

coughing and could hardly stop, or I’d get lightheaded or nauseous,” she

remembers—she checked the feed labels and noticed that they listed

roxarsone, an organic arsenic compound, as an ingredient. Concerned about

her chickens as well as her own health, she asked Pilgrim’s Pride why she

was being forced to use feed containing arsenic.

“I was told to mind my own business,” she says. “[They told me] ‘it’s a

microbe inhibitor and is proven to be safe in the quantity used in the

feed.’ But you know some of this stuff is bad when the tickets instruct

you not to feed it to any other animals due to it being proven fatal if

ingested.”

Pilgrim’s Pride, the second largest chicken company in the country, wasn’t

doing anything uncommon: over 70 percent of all broiler chickens grown in

the U.S. are fed roxarsone, according to a 2000 article published in the

journal Poultry Science. Roxarsone prevents the growth of microscopic

intestinal parasites called coccidia that frequently infect livestock, and

it provides the added bonus of better growth—i.e., bigger chickens.

(Despite repeated requests, Pilgrim’s Pride would not confirm whether it

still uses roxarsone.)

Roxarsone doesn’t disappear once chickens eat it. Some is distributed

throughout the animal’s tissues, including the breasts, thighs and

legs—meat that is later eaten by consumers. The rest is excreted unchanged

in poultry waste. Ninety percent of this manure is later converted into

fertilizer that can contaminate crops, lakes, rivers, and eventually

drinking water.

Little research, however, has investigated the public health consequences

of this practice, which was banned in the European Union in 1999. Although

several studies have looked at the levels of arsenic present in chicken

muscle meat, and some have looked at crop soil contamination, the results

have been inconsistent. None have determined how extensively this practice

contaminates drinking water.

“There’s been such a huge degree of regulatory attention paid to arsenic

in drinking water, and yet here’s this very widespread practice that has a

real potential of adding to drinking water contamination and yet nobody’s

looking at it,” says Dr. Wallinga, director of the Food and Health

Program at the Institute for Agriculture and Trade Policy (IATP), a

non-profit research and advocacy organization based in Minneapolis.

Any increase in Americans’ levels of arsenic exposure is of great concern:

The Environmental Protection Agency, which regulates drinking water,

considers arsenic a class A carcinogen, meaning that data have

definitively shown it to cause cancer. Other health effects from chronic

low-level exposure include partial paralysis, blindness and diabetes.

Although the EPA tightened its regulations for arsenic levels in drinking

water this past January, lowering it from a maximum of 50 parts per

billion (ppb) to 10 ppb, this new level still exceeds the agency’s

recommendations for exposure to a carcinogen by a factor of 50.

The EPA typically recommends that the amount of a carcinogen in drinking

water should not cause more than one person in 100,000 to develop cancer

as a result of drinking that water daily. But Americans who are regularly

drinking water containing 10 ppb of arsenic are at a 50-fold higher cancer

risk than this: in other words, one out of every 2,000 of those Americans

is likely to develop cancer because of the arsenic in their tap water. And

the EPA estimates that 12 million Americans are currently drinking water

containing more than 10 ppb of arsenic—making their cancer risk even

higher.

The EPA isn’t meeting its own safety standard for arsenic because the

recommended amounts “are set at a level which water systems cannot meet,”

according to agency press officer Dale Kemery. After preparing a cost /

benefit analysis, the EPA set its arsenic limits at a level that maximized

risk reduction while minimizing cost to the consumer, he says.

Where is all of this arsenic coming from? Most arsenic contamination

arises from natural sources or from its former use in pesticides and wood

preservatives. Though these uses have since been banned, the arsenic

remains in the environment and is extremely difficult to remove. The

poultry industry’s use of roxarsone, however, is one of the few easily

preventable ways in which arsenic enters the food chain.

Given that arsenic is already a significant health risk, many think that

its use in poultry feed should be investigated and, if found to be a

significant source of contamination, banned.

This debate isn’t so cut and dried, however, because arsenic exists in

both organic and inorganic forms, and experts disagree about the relative

toxicity of the two.

According to the FDA, which monitors the use of drugs in animal feed,

organic forms of arsenic like roxarsone, which are bound to carbon and

hydrogen, are “not considered to be carcinogens and are considerably less

toxic than inorganic forms of arsenic,” writes agency spokesperson

Herndon in an e-mail.

But the Agency for Toxic Substances and Disease Registry, part of the U.S.

Department of Health and Human Services, states that “almost no

information is available on the effects of organic arsenic compounds in

humans.” ATSDR also says that high doses of organic arsenic can produce

some of the same effects as inorganic forms.

And although roxarsone starts as an organic molecule, it doesn’t stay that

way. When a chicken eats feed containing roxarsone, most of it—about 150

milligrams over a chicken’s lifetime—is excreted unchanged in the

chicken’s waste. After 30 days, the excreted roxarsone naturally converts

into other forms of arsenic, including highly toxic inorganic forms like

arsenite, according to a study published this year in Environmental

Science & Technology.

Inorganic forms of arsenic, which are bound to oxygen, chlorine or sulfur,

are therefore present in poultry manure. “This waste is then spread on

fields near poultry farms,” writes Ellen Silbergeld, a professor of

environmental health sciences at s Hopkins University, in an e-mail.

“The poultry industry is processing and selling poultry waste as garden

fertilizer for consumers to use in home gardens and lawns.”

According to chemist Garbarino, a co-author of the study in

Environmental Science & Technology, the arsenite present in manure and

fertilizer binds poorly to soil particles, making it highly mobile in the

environment such that it can easily contaminate nearby lakes and streams.

Arsenite “is considered to be one of the more toxic arsenic species,” he

writes in an e-mail.

Roxarsone meets the FDA’s criteria for approval because it has been shown

to be safe for chickens. The compound also meets the guidelines of the

USDA, the agency that monitors food safety, because roxarsone residues in

chicken tissue don’t exceed the agency’s safety levels. However,

roxarsone’s potential downstream effects are not being addressed by either

agency. And the agency responsible for regulating roxarsone’s byproducts

in drinking water—the EPA—has no jurisdiction over roxarsone’s use in

chicken feed.

Lobb, director of communications for the National Chicken

Council—a non-profit organization representing poultry producers and

distributors—argues that toxic forms of arsenic occur naturally in the

environment and that the additional levels from the use of arsenic in

poultry feed “are just so small” that they are most likely not a problem.

“Arsenic is just there, it is elemental, it is in the rock in many, many

areas and it just occurs naturally,” he says.

The amount of arsenic released into the environment via poultry manure is

approximately 250 to 350 metric tons per year, according to several recent

peer-reviewed studies. This can be compared to natural releases of

arsenic, mostly from volcanoes, which the EPA estimates are in the range

of 2,800 to 8,000 metric tons per year. There are also other ways that

arsenic gets into the environment, including metal smelting and coal

burning, but the exact amount released from these other sources is

unclear.

How much of the “extra” arsenic entering the environment via feed is

contaminating drinking water? No one seems to know for sure. “We do not

know enough about this,” writes Silbergeld in an e-mail. “In some parts of

the U.S., naturally occurring sources of arsenic [like those found in

rocks] are a very important source of arsenic in ground water. In other

areas, disposal of poultry waste may be the most important.”

According to Fairchild, a poultry scientist at the University of

Georgia, the best way to clearly determine roxarsone’s downstream effects

is to improve the technology used in the research. While some studies have

been published on roxarsone’s effects on soil, “there’s no consistent

data,” he says. If the scientists studying it today “are using the same

old techniques that have been used for the past 10 years, I don’t think

we’re going to get any closer to the answer than we were five years ago.”

Lobb agrees that more—and better—studies would be helpful. “I think this

area really cries out for some more objective research, and I hope

somebody will supply that one of these days,” he says. “But the reason

that no one is doing it, I guess, is because there does not seem to be a

problem here.”

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