Skip to main content
U.S. flag

An official website of the United States government

Arsenic in Ground-Water Resources of the United States

June 1, 2000

Arsenic is a naturally occurring element in rocks, soils, and the waters in contact with them. Recognized as a toxic element for centuries, arsenic today also is a human health concern because it can contribute to skin, bladder, and other cancers (National Research Council, 1999). Recently, the National Research Council (1999) recommended lowering the current maximum contaminant level (MCL) allowed for arsenic in drinking water of 50 ?g/L (micrograms per liter), citing risks for developing bladder and other cancers. The U.S. Environmental Protection Agency (USEPA) will propose a new, and likely lower, arsenic MCL during 2000 (U.S. Environmental Protection Agency, 2000). This fact sheet provides information on where and to what extent natural concentrations of arsenic in ground water exceed possible new standards.

The U.S. Geological Survey (USGS) has collected and analyzed arsenic in potable (drinkable) water from 18,850 wells in 595 counties across the United States during the past two decades. These wells are used for irrigation, industrial purposes, and research, as well as for public and private water supply. Arsenic concentrations in samples from these wells are similar to those found in nearby public supplies (see Focazio and others, 1999). The large number of samples, broad geographic coverage, and consistency of methods produce a more accurate and detailed picture of arsenic concentrations than provided by any previous studies.

Publication Year 2000
Title Arsenic in Ground-Water Resources of the United States
DOI 10.3133/fs06300
Authors Alan H. Welch, Sharon A. Watkins, Dennis R. Helsel, Michael J. Focazio
Publication Type Report
Publication Subtype USGS Numbered Series
Series Title Fact Sheet
Series Number 063-00
Index ID fs06300
Record Source USGS Publications Warehouse
USGS Organization National Water Quality Assessment Program