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