David Baron of member station WBUR reports on the growing call for a near-complete ban on the use of chlorinated chemicals. Scientists say that many chlorine compounds are a central cause of environmental pollution in the Great Lakes region and elsewhere, affecting, fish, waterfowl and possibly people. A US-Canada commission which oversees the Lakes has joined the call for a ban. Users and producers of chlorine products argue that reduction of key chemicals is enough and a full scale ban is impossible and economically harmful.