ROCHESTER: Catching his breath at a fitness club, Matt McHugh took a gulp of water from his trusty, hard-plastic Nalgene 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 trendy sports accessory led a major Canadian retailer to remove Nalgene and other polycarbonate plastic containers from store shelves in early December.

"It's definitely a concern but I'd like to learn more before I make any decisions about my water bottles," McHugh, 26, a business manager for a reggae band, said with an easy laugh. "For now, I'll probably keep using my Nalgene until it breaks. It's indestructible, I've heard!"

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, a compound created by a Russian chemist in 1891.

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.

However, an expert panel of researchers reported at a US government conference that the potential for BPA to affect human health is a concern, and 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 Inc pulled polycarbonate water bottles from its 40 stores worldwide in December 2005 and, a month later, organic foods chain Whole Foods Markets stopped selling polycarbonate baby bottles and child drinking cups.