Chlorate
Riverhead WD
Chlorate forms in drinking water as a byproduct of disinfection. Chlorate impairs thyroid function, making chlorate exposure most harmful during pregnancy and childhood. Read More.
In 2002, California scientists proposed an advisory value, called an action level, for chlorate at 200 parts per billion. Between 2013 and 2015, the EPA collected data through the Unregulated Contaminant Monitoring Rule program and found that over 15 percent of water tests from 38 percent of utilities had chlorate levels above a health-protective concentration, which federal scientists defined as 210 parts per billion, nearly equivalent to the California advisory value.
Samples
Samples exceeding legal limit (MCL)
Samples exceeding
health guidelines
Testing results - average by year
Year | Average result | Samples taken | Detections | Range of results |
---|---|---|---|---|
2013 | 25.8 ppb | 12 | 8 | ND - 100.0 ppb |
2014 | 22.7 ppb | 12 | 9 | ND - 42.0 ppb |
2015 | N/A | 0 | 0 | N/A |
2016 | 27.9 ppb | 1 | 1 | 17.0 ppb - 21.7 ppb |
2017 | 38.4 ppb | 1 | 1 | 25.3 ppb - 26.2 ppb |
2018 | N/A | 0 | 0 | N/A |
2019 | N/A | 0 | 0 | N/A |
ppb = parts per billion
State and national drinking water standards and health guidelines
EWG Health Guideline 210 ppb
The EWG Health Guideline of 210 ppb for chlorate was defined by the Environmental Protection Agency as a benchmark for testing under the Unregulated Contaminant Monitoring Rule program. This health guideline protects against hormone disruption.
ppb = parts per billion
All test results
Date | Lab ID | Result |
---|---|---|
2013-09-18 | 34272 | 25.0 ppb |
2013-09-18 | 13031 | ND |
2013-09-18 | 10834 | 43.0 ppb |
2013-09-18 | 17707 | 29.0 ppb |
2013-09-18 | 12945 | ND |
2013-09-18 | 12965 | ND |
2013-09-18 | 78331 | ND |
2013-09-18 | 78329 | 27.0 ppb |
2013-09-18 | 15117 (WELL 3A) | 22.0 ppb |
2013-09-20 | 07261 | 42.0 ppb |
2013-09-20 | 62206 | 22.0 ppb |
2013-09-20 | 82064 | 100.0 ppb |
2014-03-19 | 10834 032014 | 37.0 ppb |
2014-03-19 | 12945 032014 | ND |
2014-03-19 | 15117 032014 | 42.0 ppb |
2014-03-19 | 66206 032014 | 21.0 ppb |
2014-03-19 | 13031 032014 | ND |
2014-03-21 | 12965 032014 | 31.0 ppb |
2014-03-21 | 78331 032014 | 29.0 ppb |
2014-03-21 | 17707 032014 | 29.0 ppb |
2014-03-21 | 34272 032014 | 20.0 ppb |
2014-03-26 | 07261 03/26/2014 | 41.0 ppb |
2014-03-26 | 78329 03/26/2014 | 22.0 ppb |
2014-03-28 | 72064 032014 | ND |
2016-07-11 | 27.9 ppb | |
2017-07-10 | 38.4 ppb |