First the pet food, now infant formula?

Melamine in a nutshell.

Melamine is a substance that can be combined with other chemicals to form a melamine resin which is a durable type of plastic. The end products of its use include counter-tops, glues, flame retardants, and adhesives. Melamine has been indicted as the agent responsible for the cases of renal failure and deaths related to pet foods in 2007 and more recently with the contamination of milk products and infant formula in China. Suggestions have been made that the melamine was used to elevate the protein measurements of these products. 

Most testing done to measure the protein in a product actually measures the amount of nitrogen. Since protein is one of the few foods that contain nitrogen, the indirect nitrogen test usually correlates with the concentration of protein in the product. Addition of melamine to products used for animal or human consumption increases the measurement of crude protein as the nitrogen in melamine is measured as protein. Additional testing would be needed to measure the actual amount of protein itself and identify the contaminant.

When the melamine is combined with another product, cyanuric acid, another chemical that can cause kidney stones is formed. This insoluble melamine cyanurate may lead to renal failure, particularly in cats. In China, infants who were given the contaminated formula have had kidney stones and some have had kidney failure. Infant deaths have occurred.

Currently, infant formulas made in the United States do not have any of the contaminated products. Caution should be used with the use of food products that are imported from China and are sold on side markets that are not as vigilant about food recalls.  The eating of food from an animal that had melamine in their diet does not have an obvious risk to humans.