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Paracelsus' poison

Are your melamine plates poisoning you?

This Australia Day, you might be feeling a little nervous as you slap your slightly carbonised sausages or lamb chops on a melamine plate if you have read news coverage of research just published in the Journal of the American Medical Association. Will you get more than the tomato sauce covered treat you have been looking forward to? Will you get an extra helping of melamine?

Melamine is the base chemical which makes the robust melamine plastic tableware we so love because of its durability. Melamine (the base chemical) is also infamous as an illegal adulterant in pet food and children’s milk formulas. The milk contamination event resulted in the deaths of six children and kidney problems in many more.

The levels of melamine that caused these problems was enormously higher than that we are likely to consume from our normal diet. However, long term consumption of lower levels of melamine may be associated with an increased risk of kidney stones (although the falling incidence of kidney stones in women is evidence against this idea).

Where would we get melamine from in the first place? Some research has found that placing very hot fluids (distilled water and acetic acid) in melamine plastic tableware for 30 minutes can cause melamine to leach into those fluids.

However, the effect is only really significant at temperatures from 60 degrees centigrade and up, with the highest levels found when fluids are kept at 90 degrees centigrade for 30 minutes. The relevance of this to standard food serving is unclear.

The new paper by Wu et al provides a more relevant study of melamine exposure from food. Wu et al show that hot (90 degree) soup will leach melamine from melamine plastic soup bowls and this melamine is absorbed by the body and excreted in the urine.

They showed that the melamine is very rapidly excreted. Importantly, the total levels of melamine excreted suggest an exposure to melamine over 600 times lower than the most stringent exposure limit[*]. This is despite the researchers using a brand of melamine ware with the highest melamine leaching on contact with hot fluids.

What we don’t know from this report is whether the contact time with the soup was representative of standard household or restaurant use (how many families will serve soup at 90 degrees C, not that far from boiling) and if, like the leaching experiments, the soup was held at 90 degrees centigrade for 30 minutes.

If anything, it is likely the risk from standard household use is even less than this study indicates.

The Wu et al study suggests that even with a melamine ware that has a very high level of melamine leaching, under conditions that favour melamine leaching, the level of melamine exposure that results are extremely unlikely to have any health impacts.

However, the fact that even small amounts of melamine can leach from these ubiquitous food containers at high temperatures should make us cautious.

It may be useful to test melamine tableware for melamine leaching, and only permit the sale of low leachant tableware. It may also be prudent to avoid keeping very hot foods in melamine bowls for extended periods of time.

What about your Australia Day chops? The surface of hot meat hitting your plate cools down very rapidly, and there is very much less surface area in contact with the plate (unlike fluids which evenly spread on the plastic surface), so you can bite into your chops and snags with confidence.

[*] The US FDA uses a limit of 0.063 milligrams melamine per kilogram of body weight to be the safe limit consumed daily, the WHO uses a limit of 0.2 milligrams melamine per kilogram of body weight daily

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