If you dine on chicken McNuggets, you’ll be getting a good dose of trans fats. But at least you won’t be ingesting any arsenic. That’s because MacDonalds only buys chicken meat from producers who do not feed arsenic to their chickens. Now you’re confused. Arsenic is a poison. Why would any chicken producer want to feed it to the birds it wants to sell? Because, believe it or not, in tiny doses it causes the chickens to gain weight faster and it also protects them from parasitic infections.

Since the 1970s the poultry industry has been taking advantage of arsenic’s ability to increase the efficiency of raising chickens. Of course the addition of arsenic to chicken feed needed government approval so safety studies had to be carried out. The form or arsenic that was approved for use in feed was organic arsenic. This needs a bit of clarification. The term organic here is used in its proper chemical sense, meaning that it refers to a compound that contains carbon atoms. If you want to get really technical here, the approved form was roxarsone, or in chemical language, 4-hydroxy-3- nitrobenzenearsonic acid. This compound was tested in rodents and was found to be remarkably non-toxic. But, as was later learned, in the body of the chicken, the carbon atoms are stripped away, leaving behind the inorganic form of arsenic. And with this there is an issue. Inorganic arsenic is carcinogenic. And this form of arsenic can therefore be present in chicken meat.

So why has this practice not been banned? It is a question of interpretation of toxicity data. Perhaps tainted by business interests. The European community has decided that any amount of arsenic in chicken meat is too much and has banned the use of arsenic as a feed additive. In North America, it is still allowed, the decision being based on the unlikelihood of the trace amounts of arsenic residue in the meat having any health consequences. This is probably correct. But there is a bigger question here. And that is, what happens to the vast amount of poop that is produced by the over ten billion chickens slaughtered every year.

Most of it gets spread on crop land as fertilizer or is formulated into pellets for use by the home gardener. It is now known that bacteria present in chicken litter and in the soil can convert the excreted organic arsenic into the inorganic form, and that as a result of runoff from fields it can end up in the water supply. And there is also the problem of litter dust being inhaled by farmers and gardeners. Inorganic arsenic dust is not only carcinogenic, but long term exposure can lead to neurological, hormonal and immunological effects. While so far there is no evidence that the use of roxarsone in poultry feed has led to any such problems in people, the possibility cannot be ruled out. Some of the residents of the small Arkansas town, Prairie Grove, would argue that not only is this a possibility, it is a probability. They claim the town has an unusually high incidence of rare cancers which they link to chicken manure spread on the fields that surround the town. They launched law suits against the manufacturer of roxarsone, but in the cases that have come to court, the suits were dismissed for lack of evidence. In any case, the practice of adding arsenic to chicken feed is not necessary. The Europeans have no problem raising chickens without arsenic. Why should we?

@JoeSchwarcz