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National Drinking Water Database


Total trihalomethanes (TTHMs) in Idaho


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

The Most Polluted Communities in Idaho

233 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)
1Clearwater Water Dist
Kooskia, ID
9817 of 1768.96 ppb
(39.3 to 94 ppb)
2Twenty Mile Creek Water Assn
Sandpoint, ID
30010 of 1067.39 ppb
(23.6 to 115 ppb)
3City of Salmon
Salmon, ID
3,08011 of 1262.48 ppb
(0 to 137.6 ppb)
4City of Elk River
Elk River, ID
1658 of 956 ppb
(0 to 118.3 ppb)
5Castle Mountain Creeks Owners Assn
Boise, ID
27514 of 1755.02 ppb
(0 to 135 ppb)
6City of Mccall
Mccall, ID
2,11013 of 1451.29 ppb
(0 to 84.6 ppb)
7Colburn Water Assn
Sandpoint, ID
2768 of 850.93 ppb
(21.4 to 94.4 ppb)
8Pine Ridge Water and Sewer Dist
Kamiah, ID
3903 of 347.5 ppb
(33.2 to 64.8 ppb)
9Judgetown Water and Sewer District
ID
313 of 346.7 ppb
(23.3 to 60.4 ppb)
10Elk City Water and Sewer Assn
Elk City, ID
3605 of 546.66 ppb
(11.9 to 77.9 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 Idaho

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

Violation TypeNumber of Violations
Monitoring and Reporting Disinfection Byproduct Rule94
Over maximum contaminant level, Single Sample5
Over maximum contaminant level, Average5