Perchlorate is a salt formed by the addition of oxygen molecules to chloride. It is 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 equivalent to 15 parts per billion (ppb).
Lake Mead, which is the source of approximately 90 percent of Southern Nevada’s drinking water, contains low concentrations of perchlorate. During 2012, concentrations in the treated water averaged 1.2 parts per billion (ppb). One ppb is roughly equivalent to a half teaspoon of water in an Olympic-size swimming pool.
The sources of perchlorate in Lake Mead—and downstream in the Colorado River system—are two industrial complexes in the southeast portion of the Las Vegas Valley, where perchlorate is produced 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 that complex, contaminated groundwater remains.
To capture this water and prevent additional perchlorate from entering the Las Vegas Wash, the Nevada Division of Environmental Protection (NDEP) 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.
Reverse osmosis units are generally effective at reducing perchlorate levels in drinking water to below detection limits. The Southern Nevada Water Authority encourages any customers with concerns about perchlorate-related health effects to consult with their physician.