And a study conducted in the United States suggests the kind of thorough washing that could kill bacteria might make the bottles unsafe in another way. Frequent washing might accelerate the break-down of the plastic, potentially causing chemicals to leach into the water, the study found. Preliminary research conducted by a graduate student at the University of Idaho found that with repeated use, toxic chemical compounds can migrate out of the bottles into the liquid inside. Although plastics experts contend the bottles are safe, the study ultimately concluded little is known about what happens when the bottles are used over and over again.
"The fact is, a lot of these compounds have not really been studied in terms of their human health effects," said Margrit von Braun, a University of Idaho professor. Single-use soft-drink and water bottles are commonly made of a plastic called polyethylene terephthalate (PET) which, while considered safe for its intended use, was found to break down over time. "The longer you used it, the more stuff ended up in the water," said von Braun.
One of the toxins that frequently appeared in water samples from the reused bottles was DEHA, a carcinogen regulated in drinking water because it has been found to cause weight loss, liver problems, or possible reproductive difficulties. It is also suspected that DEHA can cause cancer in humans.
Von Braun said she was surprised to discover how widespread the reuse was - and how long some people would hold on to a single bottle. "A lot of people use them for weeks, and sometimes months, literally until it's leaking," said von Braun. One survey of the campus found someone who had been reusing the same bottle for six months.
