Aquifers underlaying Nassau and Suffolk counties have been classified as the sole source of water supply for Long Island, New York, and source contamination would pose a severe threat to public health. The area has been subject to premature release of information concerning contamination, placing a heavy burden on area suppliers, who must contend with financial responsibility of cleanup operations as well as consumer fear and distrust. Aldicarb, a carbamate pesticide, and volatile halogenated hydrocarbon solvents, including trichloroethylene, tetrachloroethylene, vinyl chloride, 1,2dichloroethylene, toluene, and several of the xylenes, are covered. Includes 6 references, figures.