RISK COMMUNICATION - HEALTH RISKS ASSOCIATED WITH ENVIRONMENTALLY CONTAMINATED PRIVATE WELLS VERSUS CHLOROFORM IN A PUBLIC WATER-SUPPLY

During March 1988, 16 private wells in Sault St. Marie Michigan, were found to be contaminated with one or more environmental contaminants. In accordance with the Michigan Environmental Response Act, the state provided the affected residents with bottled water for drinking purpos es. Risk assessments for carcinogens (benzene, 1,2-dichloroethane, dic hloromethane, trichloroethylene, and tetrachloroethylene) were formula ted. The total excess cancer cases attributable to the consumption of contaminated water from these wells were estimated to be 14 per one mi llion persons. The maximum concentration of chloroform in the city pub lic water supply was 26 ug/L. The high concentration of chloroform was the result of chlorination of the unfiltered river water by the publi c water facility. The relative health risk from the consumption of chl orinated surface water from the public water supply system would be ap proximately 4.3 times greater compared to that of consuming groundwate r from the contaminated private wells. The affected residents were giv en three options: (a) continue consumption of bottled water; (b) conne ction to the existing public water supply system; or (c) construction of deep water wells. The citizens voted for the second option of conne cting to the public water supply system and voluntarily accepted the r elatively higher health risk. The State of Michigan later proposed to further improve the water purity by upgrading the public water supply system by the incorporation of a filtration plant. The project was com pleted in August 1993.