Researchers from the National Institutes of Health and the USDA's Food Safety Inspection Service recently reported alarmingly high levels of arsenic contamination in the flesh of broiler chickens . After having reviewed about 5200 chicken samples from the US, these government researchers found that the mean concentration of arsenic in young chicken was 0.39 ppm, 3- to 4-fold higher than in other poultry and meat. Based on the fact that chicken is a meat source of growing importance, it is reasonable to assume that arsenic ingested through chicken consumption has a significant influence on the arsenic intake by humans.
Whether these findings are a real threat for human health very much depends on the arsenic species present in the meat . The US poultry industry  and the pharma industry  argues that the organic form of arsenic given to chickens isn't toxic. Indeed, phenylarsonic organic arsenicals are less toxic than inorganic compounds or aliphatic and other aromatic organic compounds . "This study appears to be much ado about nothing," says Richard Lobb, the public relations Director of the National Chicken Council. He says the less toxic form of arsenic is "used responsibly and safely by poultry producers" .
However, based on the somewhat outdated and at that time preliminary results obtained by Levine  and Weiler , stating that about 65% of arsenic in poultry meat is inorganic, the researchers found that consumption of chicken meat could alone be responsible for 25% of the tolerable daily intake of 2 µg/kg/day of inorganic arsenic (WHO 1983) . In contrast, using a modern hyphenated technique (IC-ICP-MS), Zbinden et al. reported in a publication from 2000 , that about 68% of the arsenic found in chicken was arsenobetaine. To make the picture a bit more complicated, there is some indication that cooking the meat may create additional toxic arsenic by-products .
It seems, that such contrasting results call for further investigation of arsenic speciation in chicken tissues both in fresh and cooked meat.
Anyhow, how did the arsenic get into the chickens? According to the US Food and Drug Administration arsenic compounds are extensively added to the feed of animals--particularly chickens and pigs--to make them grow faster [11,12]. Most broiler chickens (which constitute 99% of the chicken meat that people eat) are fed arsenic in the United States [11,13]. Most of the animals are so heavily infested with internal parasites that adding arsenic to the feed can result in a "stunning" increase in growth rates .
Since the 1970s, the American poultry industry has used certain arsenic-based ingredients as chicken feed additives. The three major compounds in this class are arsinilic acid, roxarsone (4-hydroxy-3-nitrophenylarsonic acid), and nitarsone (4-nitro-phenylarsonic acid) . Roxarsone is currently the most commonly used arsenical compound in poultry feed in the United States, with a usage of 23 to 45 grams of chemical per ton of feed for broiler chickens for increased weight gain, feed efficiency, improved pigmentation, and prevention of parasites [12,16]. Roxarsone is used in turkeys as well as chickens . By design, most of the chemical is excreted virtually unchanged in the manure [11,16,18].
Some researchers have started to scrutinize the long-standing practice because of possible health and environmental risks. Questions about potential risks associated with the use of roxarsone center on the practice of spreading manure. Each broiler excretes about 150 milligrams (mg) of roxarsone in the 42-day growth period for administering roxarsone. Litter collected following this period contains from 15 to 50 milligrams per kilogram (mg/kg) of total arsenic. In poultry houses where more than 200 million broilers per year are raised, a volume not uncommon for major poultry-producing areas, litter that contains more than 8 x 103 kg of arsenic would be produced. Generally, the litter is used as nitrogen-containing fertilizer in nearby fields. Litter is routinely tilled into cornfields or applied to pastureland at a rate of between 1 and 2 metric tons per hectare. If a 100-hectare field was fertilized at 2 metric tons per hectare, about 10 kg of arsenic would be introduced to the environment .
Even if the relative amount of arsenic being added to soil by chicken manure might be a small percentage of the total arsenic in the soil, it has a higher mobility in water due to the sorption characteristic of arsenic in organic matter compared to arsenic sequestered by metal oxides. The high extractability of roxarsone from poultry litter suggests that roxarsone can easily be mobilized to the environment by either agricultural field irrigation or rainfall on uncovered windrows. Degradation could be possible through biotic and abiotic processes after roxarsone is mobilized . Inevitably, arsenic finds its way into the rivers, stream and even the crops that are later consumed by humans. Via the way of waste incinerators, it also may find its way to the atmosphere .
There are also some rumors, that poultry industry, like the beef industry, is steeped in evil practices. By feeding chicken litter to cattle, cows are ingesting highly toxic arsenic that's contained in the chicken litter .
Inorganic arsenic is considered one of the prominent environmental causes of cancer mortality in the world . Arsenic is a human carcinogen linked to liver, lung, skin, kidney, bladder and prostate cancers. It can also cause neurological, cardiovascular, gastrointestinal and immune system abnormalities. Diabetes has also been linked to arsenic exposure .
In view of this toxicity and the fact that organic arsenic can be transformed to more toxic species, the practice of feeding chickens even trace amounts of arsenic seems bizarre.
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