Environment: Chlorination Threat?

The more that scientists learn about man-made chemicals in the environment, the greater the dangers to public health seem to be. Indeed most specialists in the new field of environmental disease believe that 85% of all cancers are caused by exposure to substances in the air or water. These include everything from compounds in tobacco and automotive fumes to asbestos, vinyl chloride, the pesticide dieldrin, carbon tetrachloride and chloroform.

Now there is a new threat. Paradoxically, it involves chlorination, the process that most U.S. towns and cities use to kill the disease-carrying bacteria in ordinary drinking water. When water from a polluted...