The market for antimicrobial doorknobs, hospital fixtures and other products that kill germs on contact may be about to take on a coppery sheen. The Copper Development Association, a trade group for copper companies, said Tuesday that federal regulators had approved its application to market a group of copper alloys, including brass and bronze, as capable of killing bacteria and microbes effectively enough to protect human health. Copper ions can penetrate the cell walls of microbes and can disrupt reproduction and other cell functions. The approval is the first time that the Environmental Protection Agency has allowed health claims to...