A report from the Environmental Working Group, a Washington, D.C.-based nonprofit environmental research firm, says that chlorine by-products in Washington's drinking water spiked last May to levels above federal health limits. More than 40% of tap-water samples collected contained excessive amounts of chemical by-products of water-treatment chemicals. "These results illustrate the difficulties that utilities face in providing water free from potentially deadline bacteria, yet not contaminated with toxic by-products used to kill these microbes," the Environmental Working Group's study concluded.