Melamine in Humans

Melamine is a chemical that's in widespread industrial use. It's used as a starting material in the fabrication of durable plastic dinnerware and Formica countertops, and is added to certain paints as a fire retardant. Melamine has been implicated in several food-contamination scandals, notably in infant formula, but also in other dairy products and in pet food. How does melamine cause illness, and what are the safety risks going forward?

Chemistry of Melamine

• Melamine is one of a family of compounds known as the triazines. It consists of a six-membered ring (three carbons and three nitrogens) and three pendant nitrogen-containing groups called amines. Its high nitrogen content is presumed to be the reason why it was added (illegally) to several food products from China. Protein, like melamine, is high in nitrogen, and some quality-control tests for protein-based foods use nitrogen content as a quality indicator: A nitrogen test can detect if low-cost fillers such as starches have been used to increase the bulk of the food without adding nutritional content. By adding melamine to low-cost, low-quality products, the manufacturers could "trick" the test and sell low-quality products at high-quality prices.

How Melamine Causes Illness

• Based on studies in rats and dogs, melamine alone appears to be minimally toxic except at very high levels. The interaction of melamine with another triazine, cyanuric acid, appeared to be a key factor in causing illness during food-contamination incidents. Since cyanuric acid is both found as an impurity in synthesized melamine and used as a cattle-feed additive, it's not surprising that milk and meat products containing melamine could also contain cyanuric acid.

  The hydrogen-bonding capabilities of melamine and cyanuric acid are complementary, like Velcro hooks and loops. When the two chemicals are mixed together, they stick together in large, well-defined crystal structures. These structures are not as soluble in water as the single molecules. Scientists studying the nature of illness resulting from melamine ingestion believe that the formation of these melamine-cyanuric crystals in the urinary tract causes the kidney failure associated with melamine-contaminated food products.

Melamine Food Safety in Other Populations

• Although the only melamine-related deaths reported to date have been infants and animals, it's known that other food has been similarly contaminated, including dairy-based desserts and yogurt, and exported to as many as 47 countries. The extensive recalls placed on these products likely didn't completely prevent their consumption.

  Adults can also become contaminated by melamine, though the dosage required to make them sick needs to be higher than that in infants and animals. Adults have fully developed organ systems and larger mass, so a larger quantity of melamine would need to be consumed before the same symptom severity develops. Adults also eat a more varied diet, so the percentage of their food that is melamine-contaminated is likely to be lower.

  Although the dosage needed for overt toxicity is higher in adults, it shouldn't be assumed that consumption of melamine and cyanuric acid is safe for anyone, even in small amounts. An individual may have already been contaminated and not even known it: Kidney stones and kidney failure in adults, for example, may have been attributed to other causes, since these illnesses occur for other reasons beside melamine contamination.

Safety of Melamine in Household Products

• When melamine is mixed with formaldehyde (a preservative), the formaldehyde links multiple melamine molecules together, and a plastic is formed. This plastic has been used in the fabrication of inexpensive, durable dinnerware, furniture and household products. Although the starting materials (melamine powder and formaldehyde) of the plastic can be hazardous, concerns about the toxicity of the melamine resin itself in the course of normal use have not been validated in scientific studies. Burning or melting of the plastic, however, may cause the release of noxious gases.

Future Use of Melamine in Medicine

• Because of its interesting bonding properties, melamine and melamine-containing compounds are being studied as drug-delivery vehicles for implantation in the body. The safety of these materials must be evaluated on a case-by-case basis, and their interactions with other compounds already in the body must be heavily investigated, given the known capability for toxic effects.