A hard plastic is raising hard questions

A chemical used to make baby bottles, water bottles and food containers is facing increasing scrutiny by health officials in Canada and the United States. The substance is bisphenol-a, or BPA, which is widely used in the making of the hard, clear plastic called polycarbonate. Studies and tests show that trace amounts of BPA are leaching from polycarbonate containers into foods and liquids. Retailers including Wal-Mart have said they are withdrawing baby products made with it.