Poison in plastic bottleA Potentially deadly toxin is being absorbed into bottled mineral water from their plastic containers. And the longer the water is stored, the levels of poison increase, research reveals. As the sell-by date on many bottled waters is up to two years, scientists have now called for extensive further studies.

The research by world expert Dr William Shotyk - who has vowed never to drink bottled water again - will be published in the Royal Society of Chemistry's journal next month. It is sure to revive concerns about the safety of bottled water, the world's fastest-growing drinks industry, worth £1.2billion a year.

The tests found traces of antimony, a chemical used in the making of polyethylene terephthalate (PET) bottles, used by most mineral-water sellers.

Small doses of antimony can make you feel ill and depressed. Larger quantities can cause violent vomiting and even death. The study stressed that amounts of antimony were well below official recommended levels. But it also discovered that the levels almost doubled when the bottles were stored for three months.

Professor Shotyk, of Heidelberg University in Germany, said: "I don't want to shock people but here's what I know: Antimony is being continuously released into bottled drinking water. The water in PET bottles is contaminated."

He tested ground water and 15 types of bottled mineral water in his native Canada. The ground water contained two parts per trillion (ppt) of antimony. Bottled water had an average 160 ppt of antimony when opened immediately after bottling. But ground water stored in a PET plastic bottle had 630 ppt of antimony when opened six months later.

Professor Shotyk then tried the experiment in Europe, collecting 48 brands of water in PET bottles and water from its source in the ground at a German bottling plant. The water had four ppt of antimony before being bottled, the contents of a new bottle had 360 ppt and one opened three months later had a staggering 700 ppt.

Antimony finds its way into water by 'leaching' from the plastic in the same way that water absorbs flavour from a teabag. Health authorities said even the higher levels of antimony found are way below official safety guidelines, set at around six parts per billion by international environment agencies.

Elizabeth Griswold, director of the Canadian Bottled Water Association, added: "The levels do not pose a risk to humans. They are simply trace elements."

But David Coggan, a Southampton University-based epidemiologist who works with the Medical Research Council, called for further research into the findings.

He said not enough was known about the effects of antimony and how much had to be consumed before it became dangerous. Last year naphthalene, which can cause liver damage in high doses, was found in two bottles of Volvic mineral water. Bacteria which could leach into bottled water has been cited as a possible reason for rising levels of food poisoning.