Nalgene, the brand that popularized water bottles made from hard, clear and nearly unbreakable polycarbonate, will stop using the plastic because of growing concern over one of its ingredients. The decision by Nalgene Outdoor Products, a unit of Thermo Fisher Scientific, based in Rochester, came after reports that the Canadian government would declare the chemical bisphenol-a, or BPA, toxic. Some animal studies have linked the chemical to changes in the hormonal system.