Perchlorate has been detected in drinking water in 26 states and Puerto Rico, according to an occurrence study by the American Water Works Association (AWWA). Most of the detections were at levels below 12 micrograms per liter (µg/L). A microgram per liter equates to approximately one drop in 55,000 gallons.

Perchlorate is both a naturally occurring and synthetic inorganic chemical used in the United States as the primary ingredient in rocket fuel and to a lesser extent, in missiles, fireworks, explosives and air-bag inflators. The chemical can interfere with iodide uptake into the thyroid gland, disrupting its functions. In adults, the thyroid helps to regulate metabolism. In children, the thyroid plays a major role in proper development in addition to metabolism. Impairment of thyroid function may cause developmental and learning disabilities. Chronic lowering of thyroid hormones due to high perchlorate exposure may also result in thyroid gland tumors.

“The AWWA occurrence study helps define the scope of perchlorate contamination and its possible effects on drinking water systems and communities,” said AWWA deputy executive director Tom Curtis. “As more sensitive analytical methods are developed, perchlorate detection is likely to increase.”

The U.S. Environmental Protection Agency (EPA) is currently assessing the need for a drinking water standard for perchlorate. On Jan. 11, the National Academy of Sciences (NAS) released a perchlorate health effects report to inform EPA’s actions.

Other highlights from the occurrence study, which was released during a Feb. 9 AWWA webcast, include:

  • The majority of detections were not associated with EPA-identified releases of perchlorate.
  • Perchlorate was detected in approximately five percent of the nation’s large community water systems.
  • Less than one percent of all drinking water systems would be affected if a maximum contaminant level (MCL) of 20 µg/L were established for perchlorate. That would rise to four percent if the MCL were set lower at two µg/L.
  • The highest density of perchlorate detection was found in Southern California, west central Texas, along the East Coast between New Jersey and Long Island and in Massachusetts.

The occurrence of perchlorate in drinking water was analyzed and geographically mapped by compiling data from existing databases, including a national EPA study and studies by the states of Arizona, California, Texas and Massachusetts.

An unabridged copy of the report can be found online at The association also provides additional information on perchlorate and drinking water contamination at Perchlorate.cfm


Comments are closed.