Concerns about a hormone-mimicking chemical used in the trendy sports accessory prompted a major Canadian retailer to remove Nalgene and other polycarbonate plastic containers from store shelves in early December

Mountain Equipment Co-op based in Vancouver, is waiting for Canadian health regulators to finish a preliminary review in May before it reconsiders restocking its 11 stores with the reusable, transparent bottles made with bisphenol A, or BPA, a compound created by a Russian chemist in 1891.

There is little argument that the chemical can disrupt the hormonal system... it does. But scientists differ quite a bit on whether the low doses found in food and beverage containers are harmful. Of course the U.S. Food and Drug Administration sides with the plastics industry. They claim that BPA-based products do not pose a health risk.

At a U.S. government conference, an expert panel of researchers reported that the potential for BPA to affect human health is a concern. They suggested that more research is needed. The panel cited evidence that Americans have levels of BPA higher than those found to cause harm in lab animals.

Another outdoor-gear retailer based in Ventura, Calif., Patagonia Inc., pulled polycarbonate water bottles from its 40 stores worldwide in December 2005.

It's all about Nalge Nunc International, a division of Waltham, Mass.-based Thermo Fisher Scientific Inc. who manufactures Nalgene-brand bottles. The company employs about 900 people at a plant in Penfield, a suburb of Rochester.

The company would not allow executives to be interviewed.

Founded in 1949 by Emanuel Goldberg, Nalge Nunc is a lab-equipment supplier that became a consumer bottle producer in the 1970s.

A sports line of Nalgene-brand bottles offered in red, blue and yellow are popular in both high schools and college campuses.

Highly durable and lightweight, resistant to stains and odors, and able to withstand extremes of hot and cold, screw-cap Nalgene bottles are advertised as an "green" substitute for typical disposable water bottles.

In this city of Lake Ontario's southern shore, judgments about a long-admired local business were invariably leavened with sympathy.

The FDA claims that "BPA has been used in consumer products for over 50 years. In that time, there has been no evidence that BPA is harmful to humans, either as the result of dietary intake or industrial worker exposures."

More than 6 million pounds produced in the United States each year. Bisphenol A is found in dental sealants, the liners of food cans, CDs and DVDs, eyeglasses and hundreds of household goods.

Citing multiple studies in the United States, Europe and Japan, the chemicals industry maintains that polycarbonate bottles contain little BPA and leach traces considered too low to harm humans.

However: critics point to an influx of animal studies linking low doses to a wide variety of ailments — from breast and prostate cancer, obesity and hyperactivity, to miscarriages and other reproductive failures.

38 expert academic and government researchers attending a National Institutes of Health-sponsored conference said in a study published last August that "the potential for BPA to impact human health is a concern, and more research is clearly needed."

Fred vom Saal, a professor of biology at the University of Missouri and one of the study's chief authors said the panel reviewed 700 published articles on BPA, practically all published in the last 10 years. Yet U.S. health and environmental regulators "are pretending they're still in the dark," he said.