Is melamine carcinogenic?

Unless you’ve been living in a cave these last few months, you must have heard about melamine – that notorious chemical added to Chinese baby formula to increase its protein content. It killed several babies and made more than 50,000 seriously ill.

The acute effect of melamine is the formation of renal crystal or kidney stones, leading to kidney damage. Little children are especially susceptible to the effects of melamine because of their small body weight and their high intake of melamine-tainted milk. 90% of those who were ill were younger than 2 years old.

But what about the long-term effects of melamine? We may not be aware of it, but we are exposed to small amounts of melamine each day through Formica table tops, plastic kitchenware (melaware), pesticides, fabrics and fire retardants. Some of us may even be exposed to higher amounts of melamine each day in our workplace.

The fact is, before the news broke about melamine contamination of pet food last year and milk powder contamination this year, melamine was thought to be a relatively harmless substance of low toxicity. After all, hundreds of thousands of factory workers every year are exposed to melamine at their workplace. A search through the Hazardous Substances Data Bank (HSDB) indicate that “melamine itself does not seem to be important industrial hazard except if decomposed by heat.” Occupational exposure to melamine has been reported to cause “allergic and irritative dermatitis” but no permanent health problems of toxicity have been observed.

It is obvious that we do not know much melamine and its long-term effects. There were a couple of studies in animals as summarized below:

• In this study by Japanese researchers, melamine induced cancer in the urinary bladders of male rats fed melamine-spiked diets for several weeks.
• In another study, melamine in the diet of lab rats caused the formation of tumors in the urinary bladder and the ureter.
• Melamine caused the formation of calcareous deposits in the kidneys of female rats after 13 weeks of feeding melamine-containing food (WHO).

Recent studies also indicated that the toxicity of melamine increases several fold when combined with cyanuric acid, a by-product of water disinfectants and may therefore be present in tap water and swimming pools. According to this study, “although melamine and cyanuric acid appeared to have low toxicity when administered separately, they induced extensive renal crystal formation when administered together. The subsequent renal failure may be similar to acute uric acid nephropathy in humans, in which crystal spherulites obstruct renal tubules.”

To get back to our initial question: Is melamine carcinogenic?

According to this World Health Organization report on melamine:

“The WHO International Agency for Research on Cancer has concluded that there is sufficient evidence in experimental animals for the carcinogenicity of melamine under conditions in which it produces bladder calculi. There is inadequate evidence for carcinogenicity in humans (IARC 1999).”

Thus, whether melamine is carcinogenic to humans or not is something that nobody knows (yet). And what are we to do when in doubt? I’d say…we should err on the side of caution.

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