National Water-Quality Assessment (NAWQA) Program

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Quality of Water from Public-Supply Wells in the United States

by Patricia L. Toccalino and Jessica A. Hopple

About 105 million people—more than one-third of the Nation’s population—receive their drinking water from one of the 140,000 public water systems across the United States that use groundwater as their source.

Scientists from the U.S. Geological Survey (USGS) assessed water-quality conditions in source (untreated) groundwater from 932 public wells, and in source and finished (treated) water from a subset of 94 wells. A greater number of chemical contaminants (as many as 337), both naturally occurring and man-made, were assessed in this study than in any previous national study of public wells.

The objectives of this study were to evaluate (1) the occurrence of contaminants in source water from public wells and their potential significance to human health, (2) whether contaminants that occur in source water also occur in finished water after treatment, and (3) the occurrence and characteristics of contaminant mixtures.  

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For additional information about this study, please contact:

Patricia Toccalino
U.S. Geological Survey
6000 J Street, Placer Hall
Sacramento, CA 95819
Email: ptocca@usgs.gov
Phone: (916) 278-3090

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