Chlorate in Missouri Drinking Water
Ranked by max chlorate detected (µg/L) · UCMR 3 data (2013–2015) · Data from EPA SDWIS & UCMR
Chlorate in Missouri: what the data shows
Missouri 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 25 of those cities. The state average max detected level is 546.8 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 Missouri
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 Missouri
Highest Chlorate levels (µg/L)
All Missouri cities ranked by chlorate level
| # | City | Level | Level | Over HA? | Violations | Grade |
|---|---|---|---|---|---|---|
| 1 | Garden City | 1800.0 µg/L | Over HA | 77 | B- | |
| 2 | Saline | 1708.9 µg/L | Over HA | 17 | B+ | |
| 3 | O Fallon | 1530.0 µg/L | Over HA | 10 | F | |
| 4 | Liberty | 1470.0 µg/L | Over HA | 8 | C+ | |
| 5 | Poplar Bluff | 1420.0 µg/L | Over HA | 47 | C | |
| 6 | Hannibal | 1370.0 µg/L | Over HA | 34 | C+ | |
| 7 | Aurora | 1204.7 µg/L | Over HA | 90 | D | |
| 8 | Smithville | 873.0 µg/L | Over HA | 16 | A | |
| 9 | Higginsville | 845.7 µg/L | Over HA | 17 | B+ | |
| 10 | Macon | 592.0 µg/L | Over HA | 11 | A- | |
| 11 | Springfield | 590.0 µg/L | Over HA | 59 | F | |
| 12 | Blue Springs | 586.0 µg/L | Over HA | 0 | B+ | |
| 13 | St. Charles | 524.0 µg/L | Over HA | 0 | B+ | |
| 14 | Wright City | 480.0 µg/L | Over HA | 14 | C | |
| 15 | Wentzville | 402.0 µg/L | Over HA | 9 | A- | |
| 16 | Marshall | 399.0 µg/L | Over HA | 33 | B- | |
| 17 | Clarkton | 380.0 µg/L | Over HA | 10 | B+ | |
| 18 | Chesterfield | 370.0 µg/L | Over HA | 11 | B- | |
| 19 | Sedalia | 335.0 µg/L | Over HA | 60 | F | |
| 20 | Arnold | 326.0 µg/L | Over HA | 0 | B | |
| 21 | Grain Valley | 324.0 µg/L | Over HA | 1 | A | |
| 22 | Barnhart | 314.0 µg/L | Over HA | 1 | A- | |
| 23 | Jefferson City | 308.0 µg/L | Over HA | 19 | B+ | |
| 24 | Battlefield | 264.0 µg/L | Over HA | 11 | A- | |
| 25 | St. Peters | 250.0 µg/L | Over HA | 0 | B+ | |
| 26 | High Ridge | 194.0 µg/L | No | 15 | B- | |
| 27 | High Ridge | 194.0 µg/L | No | 1 | A | |
| 28 | High Ridge | 194.0 µg/L | No | 1 | A | |
| 29 | Joplin | 180.0 µg/L | No | 53 | F | |
| 30 | Beverly Hills | 161.0 µg/L | No | 4 | B- | |
| 31 | Beverly Hills | 161.0 µg/L | No | 3 | B+ | |
| 32 | Kirksville | 119.0 µg/L | No | 15 | A- | |
| 33 | Pacific | 110.0 µg/L | No | 47 | D | |
| 34 | Ozark | 105.0 µg/L | No | 65 | F | |
| 35 | Rolla | 65.6 µg/L | No | 32 | D | |
| 36 | Brookfield | 60.3 µg/L | No | 20 | A- | |
| 37 | Mexico | 20.0 µg/L | No | 0 | A- |
Frequently asked questions about chlorate in Missouri
Is chlorate in Missouri tap water dangerous?
Chlorate has no federal MCL. The EPA lifetime health advisory is 210 µg/L. 25 cities in Missouri 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 Missouri 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.