How frequently is perchlorate found in drinking water?
Perchlorate has been found in just over 4 % of public water systems nationally. Perchlorate was sampled in drinking water supplies as part of the Unregulated Contaminant Monitoring Regulation 1 (UCMR 1) program. EPA collected data on perchlorate from 3,865 public water supplies between 2001 and 2005. This included all large public water systems (serving more than 10,000 people), and a statistical sample of 800 small water systems, which together serve more than 80% of the population. One hundred and sixty (4.1%) systems reported a detection of perchlorate (in at least 1 entry/sampling point) at levels greater than or equal to 4 g/L (the minimum detection level of the test). These 160 systems are located in 26 states and 2 territories and approximately 1.9% (or 637) of the 34,331 samples collected (by these 3,865 public water supplies) had positive detections of perchlorate at levels greater than or equal to 4 g/L. The average concentration of perchlorate for those samples with positive
