A new study suggests plastic bottles release small amounts of chemicals over long periods of time. ((CBC))

The longer water is stored in plastic bottles, the higher the concentration of a potentially harmful chemical, a new study suggests.

The research, by a Canadian scientist now working in Germany, involved 132 brands of bottled water from 28 countries produced in containers made from polyethylene terephthalate, or PET. About 20 brands came from Canada.

In a paper to be published early next year, William Shotyk of the University of Heidelberg found that the concentration of certain chemicals, such as antimony, increases the longer the water sits in the plastic bottle. Shotyk's study measured concentrations for a period of up to six months.

"It's increasing over time because [the plastic] is leaching chemicals," said Shotyk in an interview during a recent visit to Ottawa, where he lectured on his findings.

Shotyk was cautious about the implications for human health, saying more research is needed. Antimony is a white metallic element that in small doses can cause nausea, dizziness and depression. In large doses, it can be fatal.

"Antimony is similar chemically to lead. It is also a potentially toxic trace element," said Shotyk.

Most of the Canadian bottle samples had initial antimony levels of about 160 parts per trillion, but six months after sitting in plastic the level had doubled.

However, the levels are still well below the drinking-water standard set by Health Canada at 6,000 parts per trillion. The World Health Organization recommends a standard of 20,000 parts per trillion.

Samples from other countries were found to have antimony levels as high as 2,000 parts per trillion or more.

'No threat to health': bottled water association

Elizabeth Griswold, executive director of the Canadian Bottled Water Association, said the study should not raise concerns among consumers about harmful chemicals in bottled water.

"The bottled water in Canada is perfectly safe for human consumption and there is no threat to health in regard to antimony," Griswold said.

Shotyk said more research is needed about how high the level of antimony can go as water is stored longer than six months.

"If you bottle water in Europe and ship it to Asia, what is the antimony concentration in that water by the time somebody buys that water and drinks it?" he said.

Shotyk said he plans to test the samples again in a year.

The Polaris Institute, an advocacy group that launched a bottled-water awareness campaign last year, says about 20 per cent of Canadians drink bottled water. The Canadian Bottled Water Association says the bottled water industry's revenue was $652 million in 2005.