Catching his breath at a fitness club, Matt McHugh took a gulp of water from his trusty Nalgene plastic bottle and pondered the idea of switching to an alternative made of glass, stainless steel or another kind of plastic. Worries about a hormone-mimicking chemical used in the bottles' construction led a major Canadian retailer to remove polycarbonate containers made by Nalgene and other manufacturers from store shelves in early December. Vancouver-based Mountain Equipment Co-op 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. There is little dispute that the chemical can disrupt the hormonal system, but scientists differ markedly on whether very low doses found in food and beverage containers can be harmful. The U.S. Food and Drug Administration sides with the plastics industry that BPA-based products do not pose a health risk. But an expert panel of researchers reported at a U.S. government conference that the potential for BPA to affect human health is a concern and 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. Patagonia, an outdoor-gear retailer based in Ventura, Calif., pulled polycarbonate water bottles from its 40 stores worldwide in December 2005 and, a month later, the Whole Foods Markets chain stopped selling polycarbonate baby bottles and children's drinking cups. Given there are comparably priced, greener alternatives, I'm quite convinced that within a couple of years, we're going to see the end of this chemical in consumer products," said Rick Smith, executive director of Toronto-based Environmental Defense Canada.