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National Drinking Water Database


Total trihalomethanes (TTHMs) in Iowa


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

The Most Polluted Communities in Iowa

706 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)
1Joice Water Supply
Lake Mills, IA
2311 of 1150 ppb
(150 ppb)
2Danville Water Supply
Danville, IA
91421 of 2183.79 ppb
(30 to 183 ppb)
3Southwest Reg Water District (Clarinda)
Clarinda, IA
2,09222 of 2282.98 ppb
(51 to 170 ppb)
4West Burlington Muni. Water Supply
West Burli, IA
3,16123 of 2381.94 ppb
(29.67 to 200 ppb)
5Arcml06 Llc - Silver Creek
Galesburg, IA
67311 of 1180.33 ppb
(40.5 to 166 ppb)
6Middletown Water Supply
Middletown, IA
53522 of 2279.81 ppb
(37.4 to 168 ppb)
7Orient Municipal Water Supply
Orient, IA
4022 of 279.5 ppb
(76 to 83 ppb)
8Sirwa - Corning/Brooks
Creston, IA
2,04921 of 2178.22 ppb
(40 to 180 ppb)
9Winterset Municipal Waterworks
Winterset, IA
4,76823 of 2377.7 ppb
(30 to 210 ppb)
10Arnolds Park Water Department
Arnolds Pa, IA
1,1621 of 177 ppb
(77 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 Iowa

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

Violation TypeNumber of Violations
Over maximum contaminant level, Average141
Failure to monitor regularly111