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National Drinking Water Database


Total trihalomethanes (TTHMs) in Oregon


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

The Most Polluted Communities in Oregon

427 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)
1Rink Creek Water District
Coquille, OR
2301 of 1148 ppb
(148 ppb)
2Shelley Road-Crest Acres Wd
Coquille, OR
4756 of 682.47 ppb
(11.1 to 125 ppb)
3Arch Cape Water District
Arch Cape, OR
20013 of 1379.97 ppb
(36.7 to 133 ppb)
4City of Monroe
Monroe, OR
60713 of 1378.7 ppb
(58.3 to 109 ppb)
5Watseco-Barview Water District
Rockaway Beach, OR
5407 of 772.51 ppb
(40.7 to 85.2 ppb)
6City of Sumpter
Sumpter, OR
1705 of 567.74 ppb
(42.1 to 101.4 ppb)
7City of Coquille
Coquille, OR
4,20520 of 2066.93 ppb
(12.7 to 113 ppb)
8City of Nehalem
Nehalem, OR
1,6008 of 866.58 ppb
(37.7 to 117 ppb)
9City of Port Orford
Port Orford, OR
1,19019 of 1966.38 ppb
(29.3 to 130.8 ppb)
10Westport Water Association
Westport, OR
5507 of 765.71 ppb
(37.5 to 113 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 Oregon

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

Violation TypeNumber of Violations
Monitoring and Reporting Disinfection Byproduct Rule202
Over maximum contaminant level, Single Sample9
Over maximum contaminant level, Average6