Chlorate
Manhasset Lakeville 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 |
|---|---|---|---|---|
| 2014 | 38.6 ppb | 13 | 8 | ND - 100.0 ppb |
| 2015 | N/A | 0 | 0 | N/A |
| 2016 | N/A | 0 | 0 | N/A |
| 2017 | N/A | 0 | 0 | N/A |
| 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 |
|---|---|---|
| 2014-04-22 | UCMR3 T12802 | ND |
| 2014-04-22 | UCMR3 T13704 | 31.0 ppb |
| 2014-04-22 | UCMR3 T13749 | ND |
| 2014-04-22 | UCMR3 T09308 | ND |
| 2014-04-24 | UCMR3 T7126T7892 | ND |
| 2014-04-24 | UCMR3 T10889 | 21.0 ppb |
| 2014-04-29 | UCMR3 DBPMAX2 | 94.0 ppb |
| 2014-04-29 | UCMR3 BPMAX1 | 96.0 ppb |
| 2014-04-29 | UCMR3 T7651 | 88.0 ppb |
| 2014-06-23 | 11509 062014 | 34.0 ppb |
| 2014-06-30 | 01328 062014 | ND |
| 2014-12-30 | 01328 122014 | 38.0 ppb |
| 2014-12-30 | 11509 122014 | 100.0 ppb |