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but arsenic isn't that bad. It isn't dioxin or PCBs or lead.
Some basic chemical math, first.
1 ppm =1000 ppb = 1 mg/L (Normal daily exposure to arsenic from food) = 1 in 1 million = 1:1,000,000 = 1 mg/kg (1/8th teaspoon in 55 gal drum)
500 ppb = .5 mg/L (FDA limits for chicken muscle meat) =1 in 2 million or 1:2,000,000 = 1 mg/2 kg (1/8th teaspoon in a 10 year old's backyard swimming pool - not a baby pool)
100 ppb = .1 mg/L (national US average for untreated well water) = 1 in 10 million or 1:10,000,000 = 1 mg in 10 kg (1/8th teaspoon in a large microbrewery's beer vat)
10 ppb = .01 mg/L (EPA and WHO limits for drinking water) 1 in 100 million or 1:100,000,000 (Not possible in the developing world, and requires municipal filtering in most of the Western US) = 1 mg in 100 kg (1/8th teaspoon in standard tanker truck)
1 ppb = 1 in one billion, effective minimal testing level = 1 mg in 1000 kg (1/8th teaspoon in a half-Olympic sized swimming pool)
1 ppt = 1 in one trillion = 1:1,000,000,000,000 = Extrapolated dioxin levels that caused genetic mutations in 50% of those exposed to Agent Orange during Vietnam. (there are a few machines that can test ppt, but they're REALLY expensive.)
1ppq = 1 in one quintillion = 1:1,000,000,000,000,000 = extrapolated dioxin levels passed from father via sperm during conception; caused many mutations. No machine can test for this concentration.
I'm sorry, but this is a place I HAVE to use metric measurements. Imperial sucks for ppm/ppb.
Unfortunately, the avian digestive systems (it's not just chickens, it's all birds) are well adapted to concentrating arsenic. Even free-range, organically fed, backyard chickens and ducks will have arsenic in their systems if the soil or the water have arsenic in them. They tend to concentrate it in their livers. Chicken livers from places with a high background arsenic level can cause a bioaccumulative, very slow arsine poisoning in humans, though fortunately, this rarely causes illness, and almost never causes death. (However, there are two documented cases of death by pate de fois gras caused by excessive consumption of goose liver raised in areas with a high background arsenic level. So watch the Beef Wellington consumption.)
Arsenic occurs either naturally in water and soil, or through contamination from pressure-treated wood and its ash, old pesticides, old rodenticides, Paris Green, some old wallpapers and paints, and certain insecticides. The former is the primary source of US arsenic contamination.
Now here's where you need a Chem degree: while some arsenic alloys/gases are really toxic, metallic arsenic is not all that toxic, and humans can adapt to it. Toxic levels start at 20 mg/L, or 20 times what we consume on a daily basis. Background exposure is to arsenic is relatively safe, though inhalation of arsine gases can cause lung cancer. Dermal exposure and ingestion are not too bad - some dermatological issues, and there's a correlative incidence of skin cancer (but people who live where arsenic levels are high also tend to get a lot of unblocked sunlight, so the stats aren't clear). People who live in areas with legal levels of arsenic in the water have higher tolerances - toxic levels start at about 200 mg/L.
Getting 1-2 mg of arsenic in food every day is normal - vegetables absorb it too. (An interesting historical side note is that 19th century Austrian mountaineers intentionally ate arsenic as a tonic and to help with altitude sickness; they also gave it to their horses. The Austrian death rate was not significantly lower than that of the rest of the European population at the time, and Austrian horses were considered excellent in what would become Germany.)
Arsenic is a micromineral that we seem to need in very small amounts, and we both absorb very little and excrete it easily. We absorb 5% of the arsenic we ingest, and excrete 95%. There are 10-20 mg in the average body at any given time, and we excrete what we don't absorb in 48 to 72 hours.
WHO's limits on arsenic are .01 mg/L. Organic arsenic is well tolerated; the ones we have to worry about are the gaseous and oxidized versions.
Back to Chicken: What is fed to chickens is organic arsenic (not organic as in gardening, but organic as in having stable, carbon-hydrogen bonds rather than free, unstable bonds. Think chem major, not hippie farmer).
The good news is that arsenic has an antimicrobial effect, so chicken farmers who still use arsenic are less likely to have birds that will contract and transmit avian diseases (including avian flu, among others). It effectively protects wild bird populations in the area, as well as humans and domesticated mammals.
Currently, there is a lot of arsenic research coming out of India and Bangladesh right now. They have arsenic in the drinking water at levels of from .01 to .05 mg/L. FWIW, Colorado ground water tests on average at .03 mg/L.
In areas that have .01 mg/L of arsenic in the water, rice, potatoes, radishes and onions accumulate arsenic at rates of 10 mg/kg, 4.41 mg/kg, 13.4mg/kg and 25.2 mg/kg respectively. Compare to chicken: .5 mg/kg is the UPPER limit.
The other good news is that chicken muscle does not retain arsenic at all well - .001-.325 ppm are normal, and FDA limits are .5 ppm. We get more arsenic in our potatoes than our chicken.
Tyson (and Kirkland!) does not use arsenic (and there are others who don't, as well) and any chicken labeled antibiotic free doesn't use arsenic. (But please recall that no chickens are fed hormones or antibiotics as a routine part of their diet; they get antibiotics only when they're sick, and hormones never.)
(And on another interesting historical note, arsenic was the first effective medication in the battle against syphilis. From about 1905 when Salvarsan was first refined until the widespread availability of penicillin in the 1940s, the only way to cure many bacterial infections was with an arsine compound. So lives have definitely been saved...)
Not saying that arsenic is NOT bad stuff - it's definitely not what I want in my salt shaker - but compared to dioxin, PCBs, phenyls, aromatic hydrocarbons, sodium sulphates, phosphates.... I'll take arsenic.
(And thanks for taking the time to read this - when I write this stuff out, I get to understand the laws I have to understand a LOT better. Which means I can explain them to others without feeling like I've beaten myself up with a hammer!)
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