Is bottled water bad for you?
Plastic water bottles have become part of the average Kiwi's daily kit. In a bid to stay hydrated many of us spend a lot buying bottles of water. But should we be throwing them out after a single use?
Put simply, most plastics are made of long chains of hydrocarbon molecules built from simpler blocks called monomers. When plastics break down they release small amounts of monomer chemicals and ingredients. This process happens more quickly when plastic is heated; for example, when a bottle is left in a car or put in a microwave.
Recently, attention has focused on whether such breakdown processes can occur in plastics after relatively short periods. Experts say it is possible, as are health risks associated with plastic degeneration.
Chris Winder, professor of toxicology at the Australian Catholic University, says the only well-established risk from reuse of plastic bottles is bacterial contamination. This can be resolved with proper washing and rinsing after each use. Given that heat aids the breakdown of chemicals, it's best if this is done in cold water.
Plastic bottles are generally made of two sorts of plastics - polycarbonates (made from Bisphenol A or BPA) and PET (made from polyethylene terephthalates).
Polyethylene is generally considered safe; it's BPA, which has been in commercial use for making plastics since the 1950s, that is getting a lot of bad press in toxicology and science circles.
BPA is known to leach from plastic containers into their contents. The chemical was detected in the urine of 95 per cent of humans sampled in the US (including pregnant women), with higher levels in children, so we are all exposed. This should raise a giant red flag, experts say.
BPA is structurally similar to some sex hormones and has, since the '30s, been recognised as an oestrogen mimic and disruptor. Professor Winder says BPA has been linked (in animal studies) to health problems including developmental and reproductive concerns, infertility, obesity/hypertension, diabetes, thyroid concerns and central nervous system problems such as attention deficit disorder. Breast and prostate cancer have also been reported in some animal studies, he says.
Opinions vary about the health risks of BPA. In some quarters, toxic effects in high-dose animal studies are not considered suitable for human risk characterisation.
That said, action is ramping up to ban the chemical. Canada's food regulator has banned its use, calling it a toxic chemical, and the US and the EU are looking to reduce the level of BPA products being sold. In Australasia, Food Standards Australia New Zealand does not consider their use a health risk but has introduced a voluntary phase-out of polycarbonate bottles.
Bad press is causing drink manufacturers to look for other plastics, Winder says. "People who put their drink in this type of plastic are looking for alternatives... this chemical is on its way out. Within 10 years most regulators will have taken steps to do something about it and within 20 it will be gone," he says.
One litre of bottled water costs up to 1500 times more than one litre of tap water and in New Zealand we have the luxury of good-quality tap water, yet bottled water sales have been a marketing success story, with sales slowing only recently.
Bottled water manufacturing industry revenue is expected to drop 0.1 per cent next year (IBISWorld 2012) and, according to Roy Morgan research, the proportion of our neighbours across the ditch, Australians, who prefer bottled water to tap water has fallen 20 per cent over five years from 24 per cent in 2008 to 19 per cent last year. About 20,000 Australians were interviewed a year over the period. It was found that people of all ages are now less likely to believe in bottle water's superiority.
Jon Dee, former NSW Australian of the Year and founder of Do Something!, puts the results down to awareness of possible health risks and environmental concerns.
"We are having a lot of success in getting schools to get rid of bottled water on health grounds. Dentists say there is a return to tooth decay in young kids at the levels we saw before Australia fluorinated tap water in the '50s and '60s - that's another good reason to use the tap or bubbler," he says.
It has become almost fashionable to carry an aluminium or steel water bottle. Melbourne Fashion Week organisers banned plastic bottles at this year's event and replaced them with reusable aluminium bottles and refilling stations. The recent TedxSydney event did the same.
Dee says his family uses glass bottles, which "aren't always practical so if you are going for steel or aluminium and there is a plastic lining inside, make sure it's BPA free".