Should you avoid eating hot food from plastic bowls and dishes?

by Dr Ian Musgrave and Professor Chris Winder

A: Sometimes. Not all plastics are safe, but those approved for use with food are safe to eat from.

 

They may not stack up well next to Grandma's gorgeous old dinner set, but plastic plates and bowls hold an important place in our 21st century homes – particularly for those of us living with porcelain-plate-breaking, fine-china-bowl-smashing young children.

Unlike ceramics, however, components of some types of plastics are known to be hazardous to human health.

But if you transfer hot food straight from the oven, stove or microwave into a plastic serving bowl can toxic components from the plastic leach into your food and make you ill? Should you avoid eating hot food out of plastic plates or bowls?

The risk is pretty low, says toxicologist Dr Ian Musgrave from the University of Adelaide.

"People perceive plastics in food as being a lot riskier than they really are," says Musgrave.

"There is no thing with zero risk, but based on our best information, the risk associated with plastics migrating from our food containers, that are approved for use, is insignificant."

What's really in your noodle soup?

Although there are many different plastics, the two main types of plastic used in dinnerware are melamine resin and polypropylene.

Melamine resin is a tough plastic that can be found in children's dinner sets, many picnic sets and those noodle soup bowls you see on high rotation in food courts.

On its own, the compound melamine is toxic to human health. Ingested at high concentrations, it can damage the kidneys, as was the case in 2008 in China when six babies died and 50,000 others were hospitalised after being fed baby formula contaminated with melamine.

But what does research have to say about the risk of exposure from melamine resin bowls?

A recent study from Taiwan showed that people who consumed hot soup, which was 90 degrees Celsius when poured into a melamine bowl, did excrete small amounts of melamine in their urine, indicating that melamine from the soup bowl had been absorbed into the body.

Despite these findings, Musgrave says, it's very unlikely melamine bowls are going to do you any harm.

"There are limits to how much melamine people should be exposed to," he says, "but in terms of the risk of exposure to melamine in hot bowls, the risk is really very low.

"[This study shows that] we can put 90 degree hot soup into a plastic bowl and the melamine you would get from that is 600 times lower than the most stringent exposure limit we have."

In other words, you would have to consume hundreds of servings of very hot soup each day before you exceeded the tolerable daily intake of melamine.

It's important to note, while eating hot food from melamine bowls and plates is unlikely to be a health risk, many melamine bowls are not considered safe for heating food in a microwave. This is because microwaves heat food to extremely high temperatures.

There appears to be even less concern – which has translated into fewer studies – regarding leaching of toxins from polypropylene (recycle code 5), the other plastic dinnerware workhorse. Polypropylene bowls and plates are also considered safe to use in the microwave.

What about BPA and phthalates?

What we do know though is that neither polypropylene nor melamine contain two of the toxins that have raised concern in recent years: bisphenol A (BPA) and phthalates.

BPA, primarily found in a type of plastic called polycarbonate or PC (recycle code 7), is toxic to the body in large doses and can increase your risk of breast and prostate cancer and heart disease, among other diseases. When containers made with BPA are heated, BPA levels in food have been found to increase.

Phthalates (such as the plasticiser diethylhexyl phthalate or DEHP) are primarily found in polyvinyl carbonate or PVC (recycle code 3) and have been found to cause problems with hormones and the reproductive system.

In general, plastics that are marked with recycle codes 1, 2, 4 and 5 are unlikely to contain either BPA or phthalates.

Time for a new bowl?

The bottom line: when it comes to heat, there are no materials – short of ceramics – that don't leach something, Musgrave says.

But "whatever leaches into your food is much lower than any threshold of damage," he says.

If, however, you still want to be extra cautious, you could choose to retire old plastic bowls, says Chris Winder, professor in toxicology and occupational health at the Australian Catholic University.

Plastics are large structures (polymers) synthesized from smaller building blocks called monomers. Even in plastic polymers that are not hazardous, the monomer may still be toxic on their own. In the right conditions, old plastics are more likely to break down into their monomers, he says.

"If you have a melamine dish that's new and the monomers are very strongly bound to the polymer, then the release of the monomers is probably not that great.

"But if it's starting to get a bit old and in contact with things that would cause it to release these monomers, possibly including hot water... then I think that the risk is slightly higher."

Both Winder and Musgrave agree, however, that this is not necessarily something to worry about.

Toxicologist Dr Ian Musgrave from the University of Adelaide and Chris Winder, professor in toxicology and occupational health at the Australian Catholic University, spoke to Maryke Steffens.

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