USGS scientists evaluated a range of inorganic and organic contaminants in domestic wells from every state and Puerto Rico.
Inorganic compounds arsenic (11 percent) and nitrate (8 percent) exceeded the U.S. Environmental Protection Agency's drinking water standards in well water most often while uranium, mercury, and fluoride also exceeded standards at a smaller percentage.
Organic compounds rarely exceeded drinking water standards; however, atrazine, metolochlor, simazine, MTBE and chloroform were all detected in more than 5 percent of the wells sampled.
Since the water quality of domestic wells is not federally regulated or nationally monitored, this study provides a unique, previously nonexistent perspective on the quality of the self-supplied drinking water resources used by 45 million Americans in the United States.
This national reconnaissance study is based on a compilation of existing data from a very large number of wells sampled as part of multiple USGS programs. The USGS is continuing this research to include a broader list of contaminants from a selected set of wells to further investigate geographic patterns and the co-occurrence of multiple contaminants. Release of this information is anticipated in 2007.
The newly released study on the chemical contamination of self-supplied domestic well water is featured in the August issue of the science journal Ground Water Monitoring & Remediation a publication of the National Ground Water Association; access this article and data from http://health.usgs.gov/.