Chlorate in Minnesota Drinking Water
Ranked by max chlorate detected (µg/L) · UCMR 3 data (2013–2015) · Data from EPA SDWIS & UCMR
Chlorate in Minnesota: what the data shows
Minnesota has 24 cities with chlorate data from the EPA's UCMR 3 program (2013–2015). Chlorate exceeded the 210 µg/L EPA lifetime health advisory in 11 of those cities. The state average max detected level is 487.4 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 Minnesota
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 Minnesota
Highest Chlorate levels (µg/L)
All Minnesota cities ranked by chlorate level
| # | City | Level | Level | Over HA? | Violations | Grade |
|---|---|---|---|---|---|---|
| 1 | Savage | 6530.0 µg/L | Over HA | 5 | A- | |
| 2 | Minnetonka | 1130.0 µg/L | Over HA | 0 | A | |
| 3 | Chanhassen | 375.0 µg/L | Over HA | 0 | B+ | |
| 4 | Delano | 370.0 µg/L | Over HA | 0 | A | |
| 5 | Fairmont | 365.0 µg/L | Over HA | 3 | A- | |
| 6 | Prior Lake | 297.0 µg/L | Over HA | 1 | B+ | |
| 7 | Fridley | 278.0 µg/L | Over HA | 0 | A- | |
| 8 | Andover | 263.0 µg/L | Over HA | 3 | A+ | |
| 9 | Albertville | 262.0 µg/L | Over HA | 0 | A- | |
| 10 | Plymouth | 229.0 µg/L | Over HA | 2 | A- | |
| 11 | Isanti | 227.9 µg/L | Over HA | 2 | A+ | |
| 12 | Champlin | 208.0 µg/L | No | 0 | A | |
| 13 | Chaska | 203.0 µg/L | No | 2 | B+ | |
| 14 | Anoka | 184.0 µg/L | No | 4 | A | |
| 15 | New Brighton | 172.0 µg/L | No | 1 | A | |
| 16 | Hutchinson | 153.0 µg/L | No | 0 | A | |
| 17 | Burnsville | 136.0 µg/L | No | 0 | A- | |
| 18 | Richfield | 106.0 µg/L | No | 0 | A+ | |
| 19 | Two Harbors | 50.9 µg/L | No | 0 | A | |
| 20 | Duluth | 49.1 µg/L | No | 1 | A- | |
| 21 | Cloquet | 36.1 µg/L | No | 0 | A- | |
| 22 | St. Paul | 29.1 µg/L | No | 5 | B- | |
| 23 | Shakopee | 22.9 µg/L | No | 7 | B | |
| 24 | Roseville | 20.5 µg/L | No | 0 | A |
Frequently asked questions about chlorate in Minnesota
Is chlorate in Minnesota tap water dangerous?
Chlorate has no federal MCL. The EPA lifetime health advisory is 210 µg/L. 11 cities in Minnesota 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 Minnesota 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.