Update on Melamine in Chinese Food Supply
Workers at the Chinese baby-formula company, Sanlu, and several milk-collection agencies conspired to spike diluted milk with the ersatz protein and renal toxin melamine, according to a report in the latest issue of Science. Melamine-tainted baby formula is believed to have sickened more than 53,000 Chinese infants and caused at least 4 infant deaths over the course of this year.
In addition, Chinese workers added an emulsifier, which suspends melamine in solution, to elevate the apparent fat content of the formula. According to Science, Sanlu baby formula contained an astounding amount of melamine, 2563 mg/kg.* However, investigators found only trace amounts of a melamine byproduct, cyanuric acid, in the formula. Cyanuric acid, when combined with melamine, forms poorly soluble crystals in renal tubules.
The investigators concluded that melamine alone caused the tens of thousands of cases of renal dysfunction in Chinese infants. However, others doubt this conclusion and suspect that cyanuric acid has eluded detection because it is so tightly bound up with melamine. In last year's case of contaminated pet food, initial assays failed to detect cyanuric acid, but follow-up attempts revealed substantial amounts of the byproduct.
Eliminating melamine from the Chinese food supply may be difficult, reports Science, because of the difficulty of ensuring the purity of livestock feed in the country. Chinese authorities issued a standard for melamine levels in feed last year; however, melamine was recently discovered in eggs and fish feed in Hong Kong.
Chinese bloggers are in on the investigation of melamine, writes reporter Hao Xin at ScienceInsider. According to yesterday's post, bloggers found evidence that researchers from the Chinese Academy of Sciences offered technology for making high-protein feed with its dan bai jing ("protein essence"), which may have included melamine or its byproducts. Hao Xin writes that the Academy absolved itself of any connection to China's melamine scandal after an internal investigation in October; but the Academy also declined to report the ingredients of its dan bai jing.
In an effort to capitalize on the melamine scandal, one Chinese company is offering melamine-free dan bai jing; however, the product contains the additive isobutylidene diurea, a lawn fertilizer, writes Xin. Isobutylidene urea is not approved by the FDA for inclusion in animal feed, but it is apparently allowed by the Chinese agriculture ministry.
* On November 28, the FDA concluded that levels of melamine or cyanuric acid of 1 part per million (1 mg/kg) or less in infant formula do not pose a public health risk.
Depiction of melamine chemical structure from Wikipedia.
12/4/08 update on update: More melamine-tainted Chinese eggs have been found in Hong Kong, according to yesterday's NYT. The discovery of the contaminated eggs, the fourth discovery in less than 2 months, is the result of the random testing of Chinese foods in the territory. The level of melamine in the eggs was 4.7 ppm, which is nearly 90% higher than the acceptable melamine level in foods (other than infant formula) set by the FDA, 2.5 ppm.
