The search for the cause of the deaths and injuries to pets in the pet food recall scandal that continues to unfold continues. So far three contaminants or adulterants have been identified in the recalled foods: aminopterin (a rat poison), melamine (an industrial chemical used in dinnerware, counter-tops, and as a fertilizer in Asia), and cyanuric acid (used in swimming pools to retard the breakdown of chlorine under sunlight). The aminopterin was detected in very small quantities—not enough to cause the level or type of toxicity that has been observed. Neither melamine nor cyanuric acid has been observed to be particularly toxic nor have they been known to produce the specific problems that have been observed—formation of crystals in the kidneys leading to kidney failure.

Researchers are now considering interactions between these substances.

A chemical process that occurs between two compounds, one used to make plastics and another employed in pool chlorination, may explain how North American pets were affected, some fatally, by recalled pet food products, researchers suggest.

Cyanuric acid, which was found in urine samples from animals that died, and melamine, a compound identified in the gluten found in the recalled pet food, react with one another to form crystals that may block kidney function, researchers at the University of Guelph said yesterday.

“You wouldn’t normally expect to find those compounds in pet food, and hence nobody was really looking for it,” said John Melichercik, director of analytical services for laboratory services at Guelph. “It’s just another piece of the puzzle along the way in this particular pet food issue.”


Last week, a chemist at the Agriculture and Food Laboratory in Guelph decided to test the reaction between the two compounds in a setting similar to that of an animal’s kidney.

“Our research had taken a number of turns, and so we decided to take a look at the two substances implicated by the FDA,” Melichercik said.

The experiment resulted in the formation of a precipitate in a crystal-like form.

One problem with this hypothesis is that Russian scientists investigated the interaction of melamine and cyanuric acid long ago and found no particular toxicity. There may be more substances involved in the interaction.

Neither melamine nor cyanuric acid belongs in either human or pet foods in any quantity. How did they get there?

Several explanations have been put forward. FDA scientists have suggested that melamine (and, presumably, cyanuric acid) were deliberately added to the wheat, rice, and corn glutens to make them appear to have more protein in them than they actually did when subjected to a simple test for nitrogen. That seems to be the preferred test in quickly and inexpensively evaluating protein levels. That would raise the value of the product.

It might not only be U. S. importers who are being defrauded by this practice. China has begun to pay farmers directly for wheat with a higher gluten content.

It’s also been suggested that the contamination occurred accidentally in the shipping, storage, or processing or the wheat, rice, and corn gluten. This actually sounds pretty likely but the more distinct sources of contamination are identified the greater this problem becomes in practical fact.

I have another hypothesis. I believe that the contamination is occurring as a consequence of bad agricultural practices in China and that the melamine and cyanuric acid are actually present in the raw wheat, rice, and corn themselves.

It’s my understanding that melamine is used as a fertilizer in Asia. With a half-life of 2-3 years, it doesn’t strike me as particularly well-suited for that purpose. Some have suggested (I thought about it myself) that the cyanuric acid that’s also being found is the result of the decomposition of melamine but I think there’s another, more likely, alternative.

Atrazine is probably the most-commonly used herbicide in the world and cyanuric acid is one of the possible results when atrazine is broken down by bacteria in the soil.

So, here’s my thought. Perhaps the Chinese, spurred to increase yields by increased subsidies, have been applying massive amounts of fertilizer (melamine) and herbicides (atrazine) to their fields. The atrazine is breaking down into cyanuric acid and the melamine and cyanuric acid are being taken up into the plants themselves.

One way of testing my hypothesis would be to determine if a broad range of grain-based Chinese agricultural products contained melamine and/or cyanuric acid. I’ll start to see if I can determine whether that testing is taking place.

One last point: I see no reason to believe that this is a new phenomenon and every reason to believe it’s been going on for a long time. It takes a while for a dog’s kidneys to fail under this kind of assault (some of the tests conducted have suggested as much as 20 months).

5 comments… add one
  • I’m puzzled by your use of the term ‘half life’ in reference to melamine’s use as a fertilizer. I’m more familiar with that term in reference to radioactivity.

    Do you mean that melamine remains an effective fertilizer for two-three years?

  • It means roughly the same thing as it does when speaking of a radioactive substance, John. A “half-life of 2-3 years” means that in 2-3 years there’s half as much melamine in the soil as when it first got there through a process of chemical (in this case probably mostly bacterial) decomposition. In 4-6 years there would be a quarter as much as when you started, etc.

  • L Link

    You might be interested in the post and comments on Itchmo concerning an International Herald Tribune (IHT) article “Additive that tainted U.S. pet food is commonly used in China” (By David Barboza and Alexei Barrionuevo The New York Times; Sunday, April 29, 2007).

    The article seems to have become inaccessible from IHT and NYT, but has been posted in the Itchmo comments.

    Here is a link to the Itchmo post and discussion:

  • Thanks for the link, L. For a number of reasons it’s been my intuition that this has been going on for quite some time, perhaps forever. Note, especially, that in recent years Chinese farmers are being incentivized to engage in just this kind of practice—the government has provided higher subsidies for wheat with higher protein content.

  • “It’s my understanding that melamine is used as a fertilizer in Asia. With a half-life of 2-3 years, it doesn’t strike me as particularly well-suited for that purpose.”

    Why is that? Slow-release fertilizers have a number of advantages.

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