Perchlorate
Perchlorate is a salt formed by the addition of oxygen molecules to chlorid. It is often used as an oxidizer in solid fuels. Although perchlorate is not regulated under the federal Environmental Protection Agency's (EPA) Safe Drinking Water Act, the EPA has issued a preliminary reference dose equilvalent to 15 parts per billion (ppb).

Current concentrations
Lake Mead, the source of about 90 percent of Southern Nevada's drinking water, contains low concentrations of perchlorate. During 2012, treated water contained an average perchlorate concentration of 1.2 parts per billion (ppb). One ppb is roughly equivalent to a half teaspon of salt in an Olympic-size swimming pool.

Source of perchlorate
The source of perchlorate in Lake Mead—and downstream in the Colorado River system—is two industrial complexes in the southeast portion of the Las Vegas Valley, where these Southern Nevada facilities produced perchlorate for industrial use. Groundwater contaminated with perchlorate traveled to the Las Vegas Wash through the shallow groundwater system and subsequently entered the lake. Although perchlorate is no longer manufactured in the complexes, contaminated groundwater remains.

To capture this water and prevent additional perchlorate from entering the Las Vegas Wash, the Nevada Division of Environmental Protection has overseen the installation of an interception system that uses wells to extract the contaminated water. This system has proven extremely effective, reducing the amount of perchlorate entering the Las Vegas Wash by approximately 90 percent.

What you can do
Reverse osmosis units are generally effective at reducing perchlorate levels below detection limits. The Southern Nevada Water Authority encourages customers with concerns about perchlorate-related health effects to consult their physician.

For more information about perchlorate, see the EPA's perchlorate fact sheet.