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National Drinking Water Database


Total trihalomethanes (TTHMs) in Montana


Total trihalomethanes constitute the sum of four disinfection byproducts: chloroform, bromodichloromethane, dibromochloromethane, and bromoform. [read more]

The Most Polluted Communities in Montana

229 water utilities reported detecting Total trihalomethanes (TTHMs) in tap water since 2004, according to EWG's analysis of water quality data supplied by state water agencies

Ranked by highest average Total trihalomethanes (TTHMs) level

RankSystem Population Served Positive test results of total reported tests Average Level
(Range)
1Brady County Water and Sewer District
Brady, MT
22510 of 10126.8 ppb
(6 to 185 ppb)
2Town of Medicine Lake
Medicine Lake, MT
3572 of 287.5 ppb
(85 to 90 ppb)
3North Havre County Water Dist
Havre, MT
9015 of 1581.89 ppb
(38 to 123 ppb)
4Town of Melstone
Melstone, MT
17016 of 1671.88 ppb
(33 to 123 ppb)
5Cut Bank North Water District
Santa Rita, MT
4781 of 171.2 ppb
(71.2 ppb)
6Fort Peck Rural County Water District
Fort Peck, MT
6635 of 561.5 ppb
(55.5 to 66 ppb)
7Town of Froid
Froid, MT
1951 of 161 ppb
(61 ppb)
8Dry Prairie Rural Water Authority
MT
1,1472 of 259.5 ppb
(51 to 68 ppb)
9Custer Co Water and Sewer Dist
Miles City, MT
6001 of 154.5 ppb
(54.5 ppb)
10City of Havre
Havre, MT
9,80023 of 2354.47 ppb
(15 to 99 ppb)

Health Based Limits for Total trihalomethanes (TTHMs)

StandardDescriptionLevel
One in one million (10-6) Cancer RiskThe concentration of a chemical in drinking water corresponding to an excess estimated lifetime cancer risk of 1 in 1,000,000. Source: U.S. Environmental Protection Agency.9.8 ppb
EPA Human Health Water Quality CriteriaWater quality criteria set by the US EPA provide guidance for states and tribes authorized to establish water quality standards under the Clean Water Act (CWA) to protect human health. These are non-enforceable standards based upon exposure by both drinking water and the contribution of water contamination to other consumed foods. Source: U.S. Environmental Protection Agency.11.5 ppb
Maximum Contaminant Limit (MCL)The enforceable standard which defines the highest level of a contaminant that is allowed in drinking water. MCLs are set as close to health-based limits (Maximum Contaminant Level Goals, or MCLGs) as feasible using the best available analytical and treatment technologies and taking cost into consideration. Source: U.S. Environmental Protection Agency.80 ppb
Lifetime health-based limit, non-cancer riskConcentration of a chemical in drinking water that is not expected to cause any adverse, noncarcinogenic health effects for a lifetime of exposure. The Lifetime health-based limit (or Health Advisory, HA) is based on exposure for a a 70-kg adult consuming 2 liters of water per day. Source: U.S. Environmental Protection Agency.130 ppb
One in ten thousand (10-4) Cancer RiskThe concentration of a chemical in drinking water corresponding to an excess estimated lifetime cancer risk of 1 in 10,000. Source: U.S. Environmental Protection Agency.980 ppb
Drinking Water Equivalent LevelA lifetime exposure concentration protective of adverse, noncarcinogenic health effects, that assumes all of the exposure to a contaminant is from drinking water. Source: U.S. Environmental Protection Agency.1835 ppb
Children's health-based limit for 10-day exposureConcentration of a chemical in drinking water that is not expected to cause any adverse, noncarcinogenic effects for up to ten days of exposure. The Ten-Day health-based limit (or Health Advisory, HA) is typically set to protect a 10-kg child consuming 1 liter of water per day. Source: U.S. Environmental Protection Agency.4860 ppb
Children's health-based limit for 1-day exposureConcentration of a chemical in drinking water that is not expected to cause any adverse, noncarcinogenic health effects for up to one day of exposure. The One-Day health-based limit (or Health Advisory, HA) is typically set to protect a 10-kg child consuming 1 liter of water per day. Source: U.S. Environmental Protection Agency.10600 ppb

Violation Summary for Total trihalomethanes (TTHMs) in Montana

Data from the U.S. Environmental Protection Agency includes the following violations of federal standards in Montana since 2004

Violation TypeNumber of Violations
Monitoring and Reporting Disinfection Byproduct Rule167
Over maximum contaminant level, Average14
Over maximum contaminant level, Single Sample1