Drinking Water

More than 98% of perchlorate detections in U.S. water systems are below 4 parts per billion (ppb).

This level is 60 times lower than the recognized No Observed Effect Level.

In 2005, 34,193 water samples from U.S. public water systems were reported to the U.S. EPA.

  •   Samples with perchlorate levels above 4 ppb: 637
  •   Samples with perchlorate levels below 4 ppb: 33,556

Source: Perchlorate Occurrence Mapping (Brandhuber and Clark, January 2005)

In 2005, the U.S. EPA conducted a study to help determine the occurrence of perchlorate in water across the country. 34,193 samples were tested from U.S. public water systems. Of those, only 637 samples (1.86 percent) had perchlorate levels above 4 ppb. Half of those 637 samples (i.e., 319) were in the range of 4 ppb to 6.4 ppb. Thus, perchlorate levels were less than 6.4 ppb in more than 99 percent of water samples tested, well below the legal NAS Reference Dose standard.

Citizens interested in learning about  perchlorate levels found in local water supplies should contact the local water company. Or, if local water services are provided by a municipal utility, citizens can contact customer service (details are usually listed on the utility bill) and get information on how to contact the local water purveyor. Citizens can also visit the water supplier’s website to look for either a water quality report or Consumer Confidence Report.