Assessing water bottle safety.

Runners love their water bottles, so it's unfortunate that everywhere you turn these days there seems to be mounting controversy over their safety. First there was the rumor that washing and reusing disposable plastic bottled water containers could cause cancer. This rumor is unfounded, yet persists in many forms. Usually, these chain emails contain the notion that heating the bottle (as when washing) releases carcinogens called dioxins. Plastic water bottles do not contain dioxin, and washing and reusing them appears to be safe.

Plastic bottles may, however, contain bisphenol-a (BPA). It's less certain what effect this chemical may have on the human body. BPA is widely used in the making of polycarbonate water bottles; these are the hard, nearly unbreakable plastic bottles widely used by runners and hikers, such as those manufactured by Nalgene Outdoor. This chemical, which is also used in the manufacture of baby bottles, sippy cups, and even soda can liners, has made many recent headlines and caused a multinational scare as a possible cancer-causing compound in humans. But before you decide that toxic plastics are lurking in your kitchen, let's examine everything we know to date about BPA. To date.

First off, current research has shown that the amounts of BPA that may migrate into food and beverages from plastic containers are extremely small and are at acceptable limits that are set by regulatory agencies. So what is the origin of this health scare?

Concern over BPA has been around for a few years, and last year and again this year two studies emerged that call into question its safety. In July of 2007, a study published in the Proceedings of the National Academy of Sciences found that feeding BPA to female mice changed the color of their babies' coats. The mice with brown coats grew up with healthy weights, while those with yellow coats grow up to be obese, with a higher susceptibility to cancer and diabetes. In April of 2008, The National Toxicology Program in the United States released a draft report stating that some rats that were fed or injected with low doses of the chemical developed precancerous tumors and urinary tract problems and reached puberty early. While the report said the animal tests provided "limited evidence," it also noted that the "possibility that bisphenol-a may alter human development cannot be dismissed."

But all of the data so far comes from animal studies. The draft report noted that there is no direct evidence that human exposure to BPA harms reproduction or infant development, as it did to some mice. The only time that BPA has been shown to have significant effects in humans is in the case of workers who were exposed to the substance while on the job. As a result of long-term exposure to high levels of BPA in the air at their workplaces, some of these individuals experienced irritation of the eyes, respiratory tract, and skin. These symptoms resulted from inhaling BPA, not from ingesting it through foods and beverages. The experiences of these workers are not applicable to the experiences of the general public. The U.S. Environmental Protection Agency (EPA) currently believes that BPA is safe and has set a maximum acceptable dose of 0.05 milligrams per kilogram (2.2 pounds) of body weight.

But more fuel to the fire came in late April when the Canadian government declared, under that country's environmental protection act, BPA a toxic substance. Canada has only banned the substance outright in the manufacture of infant bottles, however. The country has also begun a study to monitor BPA exposure among 5,000 people to assess any danger to adults. As of now, Canada official position is that polycarbonate containers of all types are safe for anyone over 18 months of age.

Yet still more national attention to polycarbonate water bottles came in April when Nalgene Outdoor announced that it would discontinue production of consumer bottles containing BPA. The Rochester based company explained that this was due to consumer demand for BPA-free alternatives to their popular polycarbonate bottles, and did not stem from their belief that the containers were hazardous.

If the government cannot entirely rule out the possibility that trace amounts of BPA are harmful to humans, we may be wise to ask how much BPA we are exposed to. It is estimated that the typical adult is exposed to I microgram of BPA for every kilogram of body weight. One microgram is .001 milligrams, and so these levels are well below The EPA's limit. Babies who use polycarbonate bottles and canned formula are said to receive 10 micrograms per kilogram of body weight, which is still well below the EPA's limit.

If you're concerned about the trace amounts of BPA your family may be ingesting, look on the bottom of water bottles and food storage containers for the number "7" in the recycle triangle. However, most human exposure to BPA occurs through the lining of canned foods and drinks. Canned soups, fruits, and vegetables are often processed at high temperatures and contain the highest trace amounts. Even canned products labeled "organic" have a can liner containing BPA.

So what's the best way to lower your exposure to BPA? Switch to fresh fruits and vegetables, something you ought to already have done a long time ago anyway.

American Council on Science and Health, Dec. 19, 2007, "Top Ten Unfounded Health Scares of 2007 #10: Water Bottles Cause Cancer," http://www.acsh.org/publications/pubID.1659/pub_detail.asp

Health After 50, 2007, Vol. 19, No.8, p. 8

The New York Times, Apr. 18, 2008, "Bottle Maker to Stop Using Plastic Linked to Health Concerns," by lan Austen, http://www.nytimes.com/2008/04/18/business/18plastic.html?scp=4&sq=BPA&st=nyt

The New York Times, Apr. 22, 2008, "A Hard Plastic is Raising Hard Questions," by Tara Parkerpope, http://www.nytimes.com/2008/04/22/health/22well.html?sq=BPA&st=nyt&adxnnl=1&scp=3&adxnnlx=1209769510-ll+Ek5tkkT0c+7RIQG+rMw