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Plastic bottles

Plastic bottlesWhat do the claims about plastics involve?

A group of hoax emails have been doing the rounds for a few years warning about the so-called dangers of plastic bottles, containers and films. The emails generally warn people about reusing plastic bottles, freezing water in them or leaving them in cars. Some of them also talk about microwaving food in plastic containers or covered with plastic films.

However, there is no convincing scientific evidence to back up these claims or to suggest that any of these products could cause cancer.

Where do the claims come from?

Hoax emails have circulated claiming that reusing, heating or freezing water bottles releases cancer-causing chemicals called dioxins.Some also mention a chemical called DEHA, a chemical found in plastics that the emails claim could potentially cause cancer.

Some of these emails credit the warnings about plastics to Johns Hopkins University in America, but the university denies any involvement. On their website, they say:

“The Internet is flooded with messages warning against freezing water in plastic bottles or cooking with plastics in the microwave oven. These messages, frequently titled “Johns Hopkins Cancer News” or “Johns Hopkins Cancer Update,” are falsely attributed to Johns Hopkins and we do not endorse their content.”

Other versions of the emails say that the claims are endorsed by the Walter Reed Army Medical Center. Again, this is not true.

Is there any truth in the claims?

There is no convincing scientific evidence to substantiate these health warnings against plastics. 

In the UK, there is legislation in place to ensure that all materials that come into contact with food, such as containers for pre-packed food, are thoroughly tested for safety before they can be used.

Can I freeze or reuse plastic bottles?

Professor Rolf Halden of Johns Hopkins' Bloomberg School of Public Health has said that freezing actually works against the release of chemicals. He also says that it is not even clear if plastics contain dioxins, the group of chemicals specifically mentioned in the hoax email. Halden stressed that people should not be afraid of drinking water because of “miniscule amounts of chemical contaminants present in [their] water supply."

There is nothing to suggest that storing water in plastic bottles is unsafe or that a glass bottle would be any better. The types of plastic bottles in which drinking water is typically sold are safe to re-use as long as their condition hasn’t deteriorated and you can clean them. They should be cleaned with hot, soapy water and thoroughly dried every time you refill them, to prevent bacteria from growing.

Can I microwave food in plastic containers or covered in plastic film?

There is no scientific evidence that microwaving food in plastic containers or wrapped in clingfilm can affect the risk of cancer.

You can use cling film and plastics in the microwave, but make sure you use them properly and in line with the instructions on the packet, for example make sure the cling film doesn’t touch the food.

If you’d like more information about cooking safely in the microwave, look at Johns Hopkins University recommendations or the US Food Safety Inspection Service website.

Do plastics release dioxins and are they harmful?

Dioxins are a group of chemicals that are formed unintentionally by industrial processes such as burning fuels and incinerating waste. Only one dioxin, known as TCDD, has been shown to cause cancer in people.

Burning some types of plastic, such as PVC, at very high temperatures can release dioxins into the atmosphere. But there is no evidence to support the idea that dioxins are produced when plastics are heated in a microwave oven, as opposed to actually burned in an incinerator. And it is not even clear if plastics used in water bottles or films contain dioxins in the first place.

Do plastics release DEHA, and is it harmful?

DEHA is a chemical found in some plastics. However, there is no convincing evidence that DEHA is actually present in plastic bottles or plastic wraps.

Even if it was, the US Environmental Protection Agency (EPA) said that DEHA "cannot reasonably be anticipated to cause cancer" or other health problems. And the World Health Organisation International Agency for Research on Cancer has looked at all the evidence for DEHA and concluded there was no evidence to support its classification as a carcinogen.

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Updated: 30 October 2014