Can your plastic water bottle give you cancer?


Leaving your water bottle in the car on a hot day can give you cancer! This was the message of a recent email I, and no doubt many of you, received. The claim is that as the plastic bottle heats up it leaches potentially carcinogenic chemicals into the water.

Public reactions to the email seem to swing from those who immediately discarded it as scare mongering, those who believed it utterly and resolutely determined to avoid all plastics from now on and the bulk of us somewhere in the middle who thought it sounded plausible but surely if it were true the food standards people would be taking steps to warn and protect us. I made it my mission to find out what I could to uncover the real story.

The truth is that we really don’t know enough about chemical leaching from plastics and much more research needs to be done. Plastics are ubiquitous in modern society and are hard to avoid in the packaging, manufacturing, storing and reheating of foods and drinks. It’s little wonder when you consider what incredible materials they are: pliable, lightweight, hard to break and, depending on the plastic, resistant to a range of temperatures from the freezer to the microwave. But does such versatility come at a price?

“The truth is that we really don’t know enough about chemical leaching from plastics and much more research needs to be done.”

Reassuringly there are several plastics commonly used for our foods that have no evidence of harm if used in the way they were intended. The key to knowing which ones are safe is in the recycling code on the bottom of the container. Three out of the seven codes have question marks over their safety, while the remaining four have no known risk. The single-use water bottle of the email claim falls on the safe side as these are almost always recycle number 1 (PET). However this assumes you discard the bottle after drinking the contents. These bottles are not designed for repeated use and although no strong evidence that chemicals can leach as the bottle ages, it seems prudent to play safe and not take the chance.

The major concern is over a chemical called bisphenol-A (BPA), used to make polycarbonate plastics (identified by recycle number 7), epoxy resins and some other products. BPA was first synthesised in 1891 so it has been around for a long time, although it was not approved for use in food containers until 1963. However in the last few decades our use of plastics has grown enormously and consequently we are exposed to more BPA than ever before.

On a global scale it is estimated that around 2.8 million tons of BPA are produced every year. It is so widely used due to it’s hard to beat qualities for creating a hard, clear, and almost unbreakable plastic. For that reason polycarbonate plastics are used to make drinks bottles, food containers and most worryingly baby bottles and children’s sippy cups. In food manufacturing epoxy resins are used to line some food cans to help prevent corrosion and food contamination.

” For that reason polycarbonate plastics are used to make drinks bottles, food containers and most worryingly baby bottles and children’s sippy cups. “

A US Centers for Disease Control (CDC) study in 2004 found traces of BPA in the urine of nearly all of the 2,157 participants tested. Somewhat reassuringly the levels found were some 1000 times lower than the considered safe levels given by the US Environmental Protection Agency and the European Food Safety Authority. However there is no real consensus as yet on whether we have the safe levels correct with various expert panels around the world contradicting each other over whether there is a real health threat.

So what could the effects on our health be? Well BPA is what is known as an endocrine disrupter. It mimics the natural female hormone oestrogen and can therefore bind to oestrogen receptors in the body. Laboratory and animal studies to date have linked the chemical to breast and prostate cancer, to decreased sperm counts in rats, and to altered menstrual cycles and diabetes in developing mice. The greatest risk is undeniably to infants and young children; both because they are likely to have a higher exposure than adults, given that so many of their bottles and cups are made using BPA, and because the dose to body size is so much greater.

Of course we are exposed to several other oestrogen-like substances, including those found naturally in soy and soy products. There continues to be disagreement over whether those naturally occurring do us good or harm, but some (including of course the chemical industry) argue that BPA can have no more effect than those naturally present in our diet. I’m afraid I for one cannot agree with this philosophy and prefer to place my trust in nature.

Heating or placing hot food or liquids into PC plastics may increase the risk. A study released earlier this year from the University of Cincinnati showed that many polycarbonate reusable water bottles leach BPA into the water they contain at room temperature, but when exposed to hot liquids the leaching was some 55 times faster. Heating your baby’s bottle in the microwave is not a good idea.

“Heating your baby’s bottle in the microwave is not a good idea.”

They also showed the leaching from the plastic lining of canned foods was far higher than the water bottles. This is particularly worrying as at present there is no way of knowing when you buy the can whether or not it has a plastic lining. The only thing you can do is get to know through trial and error which cans are plastic free – or where possible choose a different vehicle for the food eg cartons of soup.

If you are share the concerns over BPA you can dramatically reduce your exposure to it simply by taking care over the plastics you use for foods and drinks. In the US the media exposure of the potential problem has lead to some retailers, including the major chain Wal-Mart, to stop selling any baby products made from BPA. Several manufacturers of baby/child products and sports bottles have also announced that they will stop using it. Here in Australia the issue has received less attention, but BPA-free products are available.

Dr Joanna

The other group of chemicals of concern are phthalates (pronounced thay-lates), primarily used in PVC to make it soft and flexible. You’ll also find them in your nail polish and even in some perfumes.

Anti-chemical lobbyists cite animal research studies showing high doses of phthalates can disrupt the animal’s reproductive system and in some cases cause cancer.

However safety reviews from both the European Union and the US expert panels have so far concluded that such effects are not seen in humans, at least at the doses we may be exposed to (considerably less than in the animal studies).

However most of the risk may again be to our infants and young children. A study published earlier this year in the journal Pediatrics found measurable levels of phthalates in the urine of all babies tested.

However these were not thought to come from PVC products, but from baby shampoo, baby powder and baby lotion. It seems that it is not just our food and drink receptacles that may be potentially hazardous.

The conclusion has to be that we need not panic over every plastic bottle or container we use, but we should have respect for using plastics in the way outlined by the manufacturer. We shouldn’t reuse single-use containers and we should take great care with any plastics we use for hot foods and drinks, particularly those we heat in the microwave. Perhaps it’s time for a return to good old-fashioned glass and ceramic bowls.

10 Tips to reduce your exposure to potential chemical leaching

  1. Avoid plastics with the recycle numbers 3, 6 and 7.
  2. Don’t reuse water bottles with the number 1. Dispose of in recycling after single use. Buy a reusable stainless steel bottle (such as a SIGG bottle) to use where possible instead.
  3. Go back to using good old-fashioned glass and ceramic containers to heat foods and drinks.
  4. For storing foods and drinks use glass, ceramic or the safer plastics with numbers 2, 4 or 5.
  5. Don’t drink hot drinks served in Styrofoam cups.
  6. Use a non-PVC cling wrap such as one made from polyethylene – it will be labelled microwave safe. To be extra safe avoid contact with your food when heating in the microwave.
  7. If you have a baby look for BPA-free bottles (MAM have one available in Australia) or use old-fashioned glass bottles. You’ll find them online at most green or environmental-leaning baby site.
  8. Check your children’s plastic cups, drinking bottles, plates and bowls and throw away those with the recycle number 7 or with no identification.
  9. Only put plastics clearly labelled “dishwasher safe” in the dishwasher (due to the high temperature involved).
  10. Buy your meat and fish from the butcher and fishmonger directly to avoid the plastic trays and wrapping used by the supermarkets.

Understanding Recycling Numbers – which plastic is it?

Recycle symbol number What is it? Common uses in food chain Any evidence for leaching chemicals?


PET or PETE (polyethylene terephthalate) Single use bottled beverages including water & soft drinks, peanut butter container, squeezable bottles eg honey No known risk if used as intended ie only once. Some concern over possible leaching with extended use. To reduce land fill – dispose of in recycling bin and use a refillable water bottle instead when you can.


HDPE (high density polyethylene) Milk & juice containers, yoghurt cartons, supplement bottles, margarine tubs No known risk and recycles readily.


PVC (polyvinyl chloride) Clear food packaging eg refillable rice container, lunch boxes & kids backpacks Increasing concern over potential leaching of phthalates, chemicals linked to child development problems. Does not recycle well. Avoid where possible.


LDPE (low density polyethylene) Bread bags, frozen food bags, squeezable bottles eg honey, mustard, microwave safe cling wrap No known risk and can be recycled.


PP (polypropylene) Dishwasher & microwave safe reusable containers, takeaway containers, ready to eat fruit containers, kids cups, ketchup bottles, yoghurt cartons & margarine tubs PP has a high melting point and therefore is safe for heating food in the microwave and can go in the dishwasher. No known risk of chemical leaching and can be recycled.


PS (polystyrene) Meat trays, cups & plates, Styrofoam cups Concern over leaching of chemicals such as styrene, a possible carcinogen, particularly on long storage (after a year) and when used for hot liquids or foods. More difficult to recycle. Avoid where possible.


Other – anything other than the 6 above and can be a combination of resins used. Includes PC (polycarbonate) Most baby bottles (unless labelled BPA-free), sippy cups, children’s hard plastic plates & bowls PC contains bisphenol-A (BPA) that has been shown to leach into contents. BPA has been linked to health problems including cancer & child development issues. While not all plastics with the number 7 contain BPA you will often not know. To be safe avoid them all.

This post was originally published on Dr Joanna’s website, which you can find here.

Dr Joanna McMillan is the Vice-President of the Australian Lifestyle Medicine Association (ALMA), a member of the Dietitians Association of Australia and The Nutrition Society, and an Ambassador for the Skin & Cancer Foundation.

Looking for more like this? Try:

A foolproof way to drink more water (and love it).

How to deal with constipation. Yes, we’re going there.

The 7 major health repercussions of not drinking enough water.