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National Drinking Water Database


Total trihalomethanes (TTHMs) in Texas


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

The Most Polluted Communities in Texas

3,635 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)
1Brazos River Authority Possum Kingdom Dam
Graford, TX
453 of 3234.67 ppb
(230 to 239 ppb)
2Lakeshore Sites Water Co
Haskell, TX
1481 of 1210.5 ppb
(210.5 ppb)
3Rolling Hills Subdivision
Shelbyville, TX
421 of 1202 ppb
(202 ppb)
4Preston Shores Water System
Wichita Falls, TX
2,01011 of 11198.2 ppb
(148 to 233 ppb)
5Thunderbird Bay Subdivision
Dallas, TX
8009 of 9192.56 ppb
(136 to 222 ppb)
6City of Edcouch
Edcouch, TX
2,87412 of 12182.56 ppb
(137.8 to 229.2 ppb)
7Ridgecrest
Dallas, TX
1,43410 of 10179.41 ppb
(121 to 237 ppb)
8Coles Cossing
Mont Belvieu, TX
2409 of 9172.42 ppb
(92.8 to 215 ppb)
9Arrowhead Lake Lots Water System
Wichita Falls, TX
1,9176 of 6169.78 ppb
(23.9 to 237 ppb)
10Jones Creek Terrace
Freeport, TX
90013 of 13169.48 ppb
(59.5 to 239 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 Texas

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

Violation TypeNumber of Violations
Over maximum contaminant level, Average2,158
Over maximum contaminant level, Single Sample209