Chlorate in drinking water
A byproduct of disinfecting with chlorine dioxide or stored hypochlorite.
Health: Can affect the thyroid at high levels.
210 ppb
EPA reference concentration
Across the US
4,729
systems with results
3,273
detected at least once
1,823
results above the health guideline
Those 1,823 systems serve about 131.7 million people.
From EPA's earlier unregulated contaminant testing (UCMR 3). These results are older, so ask your utility for current data.
Highest results
| Water system | People | Highest result |
|---|---|---|
| Cliffdale West Water System | 15,220 | 22,000 ppb |
| Harris County Water Control & Improvement District 36 | 11,073 | 13,600 ppb |
| City of McFarland | 14,161 | 12,000 ppb |
| Danvers Water Dept. | 28,087 | 11,000 ppb |
| Volusia County – Southwest Water System | 19,672 | 9,541 ppb |
| Volusia County – Halifax Plantation (Water Treatment Plant-8) | 6,630 | 7,208 ppb |
| Alco Water Service | 56,253 | 6,900 ppb |
| Savage Water System | 30,285 | 6,530 ppb |
| Lake Utility Services Inc North | 24,798 | 6,400 ppb |
| Willingboro Municipal Utilities Authority | 35,000 | 5,756 ppb |
| Lindenhurst Water System | 14,500 | 4,620 ppb |
| New Mexico State University Water System | 24,000 | 4,512 ppb |
| Windermere Community Water System | 21,231 | 4,510 ppb |
| St. Marys Water System | 19,994 | 4,430 ppb |
| Portage Water System | 46,292 | 4,256 ppb |
| Southern Utilities | 69,735 | 4,080 ppb |
| Bayleaf Master Water System | 16,715 | 4,000 ppb |
| Northwest Water System | 28,082 | 3,760 ppb |
| Gettysburg Municipal Authority | 12,425 | 3,730 ppb |
| Pennsville Twsp. Water Depart. | 13,500 | 3,519 ppb |
| City of Bonham | 10,746 | 3,242 ppb |
| City of Paso Robles Water Division | 31,176 | 3,100 ppb |
| City of Lemoore | 27,185 | 3,100 ppb |
| Portland Water Bureau | 666,200 | 3,000 ppb |
| Ruidoso Water System | 15,947 | 3,000 ppb |
States with the most detections
- California: 429
- Texas: 236
- Florida: 204
- New Jersey: 156
- Massachusetts: 153
- Pennsylvania: 128
- New York: 128
- North Carolina: 114
- Illinois: 112
- Ohio: 99
- Tennessee: 95
- Washington: 93
Sources
The limits, health goals and health effects on this page come from these EPA sources. The results come from EPA's monitoring data for each water system.
- EPA: UCMR occurrence data (the test results)
- EPA: National Primary Drinking Water Regulations (limits and health effects table)
This page summarizes public regulatory information. It is not medical advice. How we source and check this site.
Questions
What is the safe level of Chlorate in drinking water?
There is no federal legal limit. EPA reference concentration: 210 ppb.
Source: U.S. EPA drinking water records and PFAS testing (UCMR 5). How we read the data.