Q & A Library

Updated on 4/4/2005

You may have heard about results of two studies, one from Canada and another from the University of Idaho.

The Canadian study found that reused water bottles carried by youngsters at an elementary school were contaminated with bacteria, including fecal coliforms. Researchers speculated that the bacteria came from the hands and mouths of the children who probably didn't wash their hands very often, and that the bottles weren't being washed at home frequently. Results of the Canadian study were published in the Canadian Journal of Public Health (March 2003) and school officials in the Calgary town where the study was conducted advised parents to make sure that the bottles were brought home and washed properly and frequently.

The other study looked at what could happen if you do wash plastic water bottles well enough to kill bacteria. Here, researchers found that frequent washing might accelerate the breakdown of the plastic, possibly causing harmful chemicals to leach into the water or other beverages in the bottles. One of the chemicals the researchers identified was the carcinogen DEHA, suspected of causing cancer in humans. The water and soft drink bottles studied are made of a plastic called polyethelene terephthalate (PET) and are intended for single use, but researchers said that reuse is widespread and that some people hold onto the bottles for months, sometimes until they begin to leak.

The Canadian Bottled Water Association has advised against reuse and urged that plastic bottles be recycled after a single use.

You may think it is environmentally irresponsible to throw out so many plastic bottles (as a nation, we toss 150 million daily), but given these results it may be healthier to do so. If you routinely re-use plastic water bottles, you may want to replace them after a few washings, or better yet, use the heavier clear plastic bottles made for camping. Avoid the softer opaque bottles for any liquid, as they may shed chemicals even before washing.

Andrew Weil, M.D.