Pet poison chemistry: more on cyanuric acid

So cyanuric acid was not merely a byproduct of melamine production, it was a fraudulent ingredient in its own right ...

Another Chemical Emerges in Pet Food Case - New York Times

... Two of the Chinese chemical makers say that cyanuric acid is used because it is even cheaper than melamine and high in nitrogen, enabling feed producers to artificially increase protein readings which are often measured by nitrogen levels of the feed. The chemical makers say they also produce a chemical which is a combination of melamine and cyanuric acid, and that feed producers have often sought to purchase scrap material from this product.

Competition among animal feed producers here is intense. But the practice of using cyanuric acid may now provide clues as to why the pet food in the United States became poisonous.

Scientists had difficulty pinpointing the precise cause of the deaths, for neither melamine nor cyanuric acid are thought to be particularly toxic by themselves. But scientists studying the pet food deaths say the combination of the two chemicals, mixed together with perhaps some other related compounds, may have created a toxic punch that formed crystals in the kidneys of pets and led to kidney failure.

“I’m convinced melamine can’t do it by itself,” said Richard Goldstein, an assistant professor at the Cornell University College of Veterinary Medicine. “I think it’s this melamine with other compounds that is toxic.”

On May 1, scientists at the University of Guelph in Canada said they had made a chemical discovery that may explain the pet deaths.

In a laboratory, they found that melamine and cyanuric acid may react with one another to form crystals that could impair kidney function. The crystals they formed in the lab were similar to those discovered in afflicted pets, they said...

Another quote in the article says cyanuric acid is allowed in food in China, even though it's only known use is to produce deceptive protein measurement.

On the brighter side, there are hints in other articles today that China may start taking food safety very seriously, basically requiring exporters to support the standards of the importing country. That is potentially politically explosive, however, given the poverty of the rural areas where the fraud is rampant ...