Chlorate in Oklahoma Drinking Water
Ranked by max chlorate detected (µg/L) · UCMR 3 data (2013–2015) · Data from EPA SDWIS & UCMR
Chlorate in Oklahoma: what the data shows
Oklahoma has 37 cities with chlorate data from the EPA's UCMR 3 program (2013–2015). Chlorate exceeded the 210 µg/L EPA lifetime health advisory in 26 of those cities. The state average max detected level is 545.0 µg/L. Chlorate is a disinfection byproduct that forms when chlorine dioxide or hypochlorite solutions are used to disinfect drinking water. It is most common in systems that use chlorine dioxide for taste-and-odor control or that store hypochlorite for extended periods. There is no federal MCL — the EPA lifetime health advisory is 210 µg/L. Chlorate can interfere with thyroid function by blocking iodide uptake, an effect of particular concern for pregnant women, infants, and people with thyroid conditions. Reverse osmosis and ion exchange (anion-specific) are effective at removing chlorate; standard activated carbon filters provide only modest reduction.
Cities exceeding 210 µg/L EPA lifetime HA (no MCL)
Chlorate data across Oklahoma
Each dot is a city with UCMR 3 chlorate testing data. Cities where chlorate exceeds the 210 µg/L EPA lifetime health advisory are highlighted. Size reflects population served.
Top 10 cities by chlorate level in Oklahoma
Highest Chlorate levels (µg/L)
All Oklahoma cities ranked by chlorate level
| # | City | Level | Level | Over HA? | Violations | Grade |
|---|---|---|---|---|---|---|
| 1 | Madill | 2280.0 µg/L | Over HA | 178 | F | |
| 2 | Ardmore | 2000.0 µg/L | Over HA | 188 | F | |
| 3 | Afton | 1600.0 µg/L | Over HA | 89 | F | |
| 4 | Sapulpa | 1120.0 µg/L | Over HA | 85 | D | |
| 5 | Lawton | 995.0 µg/L | Over HA | 23 | F | |
| 6 | Bethany | 970.0 µg/L | Over HA | 14 | B+ | |
| 7 | Norman | 968.6 µg/L | Over HA | 52 | F | |
| 8 | Oilton | 919.0 µg/L | Over HA | 4 | D+ | |
| 9 | Edmond | 749.0 µg/L | Over HA | 86 | F | |
| 10 | Tahlequah | 747.0 µg/L | Over HA | 56 | F | |
| 11 | Fort Sill | 746.0 µg/L | Over HA | 4 | A | |
| 12 | Mannsville | 700.0 µg/L | Over HA | 4 | A- | |
| 13 | Jenks | 622.0 µg/L | Over HA | 31 | B- | |
| 14 | Midwest City | 601.0 µg/L | Over HA | 11 | B+ | |
| 15 | Durant | 522.0 µg/L | Over HA | 104 | D | |
| 16 | Altus | 476.0 µg/L | Over HA | 162 | D | |
| 17 | Claremore | 465.0 µg/L | Over HA | 153 | F | |
| 18 | Collinsville | 459.0 µg/L | Over HA | 24 | C+ | |
| 19 | Broken Arrow | 440.0 µg/L | Over HA | 113 | F | |
| 20 | Bixby | 348.0 µg/L | Over HA | 1 | B | |
| 21 | Muskogee | 334.0 µg/L | Over HA | 246 | D | |
| 22 | Del City | 300.0 µg/L | Over HA | 12 | F | |
| 23 | Shawnee | 253.0 µg/L | Over HA | 124 | D | |
| 24 | El Reno | 248.0 µg/L | Over HA | 49 | D | |
| 25 | Tulsa | 244.0 µg/L | Over HA | 6 | D | |
| 26 | Enid | 232.0 µg/L | Over HA | 33 | F | |
| 27 | Owasso | 198.0 µg/L | No | 8 | C+ | |
| 28 | Oklahoma City | 193.0 µg/L | No | 56 | F | |
| 29 | Okmulgee | 184.0 µg/L | No | 262 | D | |
| 30 | Bartlesville | 66.9 µg/L | No | 217 | F | |
| 31 | Stringtown | 34.2 µg/L | No | 144 | D+ | |
| 32 | Sand Springs | 33.5 µg/L | No | 20 | B | |
| 33 | Stillwater | 25.4 µg/L | No | 72 | F | |
| 34 | Henryetta | 25.4 µg/L | No | 116 | F | |
| 35 | Guymon | 24.0 µg/L | No | 10 | A- | |
| 36 | Poteau | 23.7 µg/L | No | 56 | D | |
| 37 | Hartshorne | 20.0 µg/L | No | 103 | D+ |
Frequently asked questions about chlorate in Oklahoma
Is chlorate in Oklahoma tap water dangerous?
Chlorate has no federal MCL. The EPA lifetime health advisory is 210 µg/L. 26 cities in Oklahoma exceed this level. Chlorate can interfere with thyroid iodide uptake, which is a particular concern for infants, pregnant women, and people with hypothyroidism.
Where does chlorate in Oklahoma water come from?
Chlorate is a byproduct of chlorine-based disinfectants — particularly chlorine dioxide and hypochlorite (bleach) solutions. Levels tend to be higher in systems that use chlorine dioxide for taste-and-odor treatment or store sodium hypochlorite at high concentrations or for long periods. Levels vary seasonally with disinfectant use.
How can I reduce chlorate exposure?
Reverse osmosis is the most effective home treatment for chlorate, typically removing 80–95%. Anion exchange systems also work but require regeneration. Standard activated carbon filters provide only limited chlorate reduction. Boiling does NOT remove chlorate.