WaterVerge
Chlorate Contamination

Chlorate in Wyoming Drinking Water

Ranked by max chlorate detected (µg/L) · UCMR 3 data (2013–2015) · Data from EPA SDWIS & UCMR

8
Cities Tested
4
Over HA
50%
% Over HA
321.9 µg/L
State Avg
▼ 9% vs national
vs National
62
Health Violations

Chlorate in Wyoming: what the data shows

Wyoming has 8 cities with chlorate data from the EPA's UCMR 3 program (2013–2015). Chlorate exceeded the 210 µg/L EPA lifetime health advisory in 4 of those cities. The state average max detected level is 321.9 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)

Wyoming
50%
4 of 8 cities
▼ 9% below national rate (better)
National avg
59%
1866 of 3166 cities

Chlorate data across Wyoming

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.

Wyoming city water quality map

All Wyoming cities ranked by chlorate level

# City Level Level Over HA? Violations Grade
1 Laramie 870.0 µg/L
Over HA 6
C-
2 Casper 610.0 µg/L
Over HA 22
F
3 Evanston 342.4 µg/L
Over HA 12
B+
4 Sheridan 330.0 µg/L
Over HA 16
F
5 Riverton 206.0 µg/L
No 59
F
6 Rock Springs 89.0 µg/L
No 5
C
7 Hanna 69.0 µg/L
No 2
A-
8 Cheyenne 59.0 µg/L
No 36
F

Frequently asked questions about chlorate in Wyoming

Is chlorate in Wyoming tap water dangerous?

Chlorate has no federal MCL. The EPA lifetime health advisory is 210 µg/L. 4 cities in Wyoming 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 Wyoming 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.