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Total trihalomethanes (TTHMs)

Status: National drinking water standard exists

 

Trihalomethanes are cancer-causing contaminants that form during water treatment with chlorine and other disinfectants. The total trihalomethanes group includes four chemicals: chloroform, bromodichloromethane, dibromochloromethane and bromoform. Read More.

Studies conducted in the U.S. and Europe have found that drinking tap water that carries disinfection byproducts increases the risk of developing bladder cancer. In animal studies, all trihalomethanes cause liver, kidney and intestinal tumors. Some human epidemiological studies also reported an association between disinfection byproducts and an increased risk of problems during pregnancy, including spontaneous miscarriage, cardiovascular defects, neural tube defects and low birth weight.

In 2010, the California Office of Environmental Health Hazard Assessment published a draft public health goal for the trihalomethanes group at 0.8 parts per billion, or 100 times lower than the federal legal limit of 80 parts per billion for this contaminant group.

Click here to read more about disinfection byproducts.

2015:

FOUND
FOUND ABOVE HEALTH GUIDELINES

49

states detected

24,957

utilities detected

283 million

people served

49

states over health guideline

24,895

utilities over health guideline

282 million

people served over health guideline

Health concerns for trihalomethanes

Bladder cancer

Skin cancer

Harm to fetal growth and development

State and national drinking water standards and health guidelines

Health Guideline 0.15 ppb

The health guideline of 0.15 ppb for trihalomethanes was defined by in a peer-reviewed scientific study by EWG and represents a one-in-one-million lifetime cancer risk level. as a draft public health goal, the level of drinking water contaminant that does not pose a significant health risk. This health guideline protects against cancer.

ppb = parts per billion.

EPA Maximum Contaminant
Level (MCL) 80 ppb

The enforceable federal standard that defines the highest level of a contaminant allowed in drinking water.

ppb = parts per billion.

States reporting trihalomethanes in drinking water

UTILITIES REPORTING ABOVE HEALTH GUIDELINES UTILITIES WITH CONTAMINATION
State UtilitiesPeople Served UtilitiesPeople Served
California1,16842,084,0041,17642,382,207
Texas2,64025,007,2652,64725,052,686
New York1,16420,053,9421,17520,567,842
Florida1,46219,536,3701,46419,542,812
Illinois1,27612,671,0801,27612,671,080
Pennsylvania1,22310,388,7241,22310,388,724
Ohio1,05010,065,7931,05210,067,774
Massachusetts3199,070,6903199,070,690
Georgia5528,047,4115538,047,882
North Carolina7427,567,0187427,567,018
Tennessee4256,719,9384266,721,816
Virginia5276,635,6575286,636,439
Arizona3485,942,4293495,955,233
Washington6885,559,4826925,582,215
Colorado5935,510,5535945,512,004
Alabama4665,419,2834685,448,371
Michigan1604,992,8631604,992,863
New Jersey1954,979,2041974,983,204
Maryland1634,838,5211634,838,521
Missouri6504,793,7776504,793,777
Indiana5584,660,1805604,686,929
Louisiana8234,656,0608264,676,117
Kentucky3754,603,7793754,603,779
Minnesota5514,000,3015574,027,822
Wisconsin4333,783,7194353,785,528
Oregon3453,677,4353453,677,435
South Carolina3103,523,4813103,523,481
Oklahoma8393,476,3528393,476,352
Arkansas5573,059,5455613,065,849
Kansas6742,718,2406762,755,297
Connecticut2112,656,2732112,656,273
Nevada792,545,561792,545,561
Utah1752,473,5351752,473,535
Iowa5612,471,5085612,471,508
New Mexico2641,689,0842641,689,084
West Virginia3911,501,1893911,501,189
Hawaii741,345,025741,345,025
Mississippi2171,009,0102171,009,010
Rhode Island44975,52644975,526
Delaware91941,03491941,034
Idaho135871,645135871,645
South Dakota276699,754276699,754
District Of Columbia4664,5724664,572
New Hampshire130618,784130618,784
North Dakota267612,227267612,227
Alaska141585,732141585,732
Montana180548,866180548,866
Maine77516,22477516,224
Vermont163436,519163436,519
Wyoming139414,426139414,426
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Utilities with the highest amounts of trihalomethanes, 2015

ALL UTILITIES
LARGE UTILITIES
UtilityLocationTestsAverage levelPeople served
Southwest Ouachita Waterworks Inc.*West Monroe, LA2 of 2230.0 ppb8,469
Wards Chapel Water SystemFarmerville, LA2 of 2228.4 ppb1,350
Vaquero FarmsFirebaugh, CA4 of 4215.0 ppb70
Linville-haile Water SystemMarion, LA6 of 6212.8 ppb1,635
Pleasant Hills-crossroads Water SystemsJoyce, LA2 of 2210.9 ppb840
Village of Calvin Water SystemCalvin, LA2 of 2210.8 ppb591
Sardis Water SystemFarmerville, LA16 of 16205.3 ppb1,404
Mccurtain County Rural Water District #6 (kiamichi)Smithville, OK1 of 1198.7 ppb2,000
Vixen Water System EastWest Monroe, LA4 of 4197.0 ppb486
Fcsa #49/ Five PointsFresno, CA3 of 3196.7 ppb122
Winebrook Hills Water DistrictNewcomb, NY4 of 4194.0 ppb250
Village of Georgetown Water SupplyGeorgetown, LA8 of 8193.2 ppb302
Holmesville Water System*Downsville, LA10 of 10191.0 ppb1,845
Point Wilhite Ws*Downsville, LA20 of 20189.0 ppb1,950
Village of Surfside BeachFreeport, TX2 of 2188.5 ppb3,477
Vixen Water System WestWest Monroe, LA10 of 10187.2 ppb288
Jones Mcginty Water System*Jones, LA14 of 14185.7 ppb801
Fcsa #32/cantua CreekFresno, CA2 of 2185.0 ppb250
Thorne Bay, City ofThorne Bay, AK3 of 3184.7 ppb775
RyanRyan, OK6 of 6181.4 ppb894
Hidden Oaks Subdivision WsMonroe, LA8 of 8180.0 ppb315
Milford, City ofMilford, KS4 of 4177.5 ppb594
Lakewood Water SystemLufkin, TX3 of 3177.3 ppb52
Deering Utility SystemDeering, AK1 of 1175.0 ppb150
Waurika Public Works Authority*Waurika, OK5 of 5174.0 ppb1,988
Chatham Water SystemChatham, LA20 of 20171.5 ppb1,137
Westwind Mobile Home ParkLake Oswego, CA1 of 1171.1 ppb104
City of Paint RockPaint Rock, TX3 of 3170.0 ppb280
Marion County Improvement District 2Marion, KS1 of 1170.0 ppb234
Olustee Public Water SupplyOlustee, OK6 of 6169.1 ppb650

* This water utility supplies finished drinking water to at least one other water utility. The purchasing utility is not required to test for or report Total trihalomethanes (TTHMs), but it likely has the contaminant in its water supply.

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UtilityLocationTestsAverage levelPeople served
Duncan Public Utilities Authority*Duncan, OK16 of 16162.4 ppb23,000
Altus*Altus, OK15 of 15144.5 ppb21,477
Walnut Creek SUD*Springtown, TX16 of 16111.7 ppb18,528
Claremore*Claremore, OK16 of 16109.0 ppb15,873
Tri County Joint Municipal Authority*Fredericktown, PA16 of 16108.7 ppb10,100
City of Flint*Flint, MI1 of 1105.0 ppb99,763
Lemoore Naval Air StationNas Lemoore, CA20 of 20104.5 ppb11,500
City of AvenalAvenal, CA1 of 1101.0 ppb16,236
City of LemooreLemoore, CA15 of 1694.1 ppb24,945
Orange County WCID 1Vidor, TX16 of 1694.1 ppb17,681
Chickasha Municipal Authority*Chickasha, OK16 of 1693.3 ppb16,036
Benton - Washington Regional Public Water Authority*Rogers, AR6 of 691.3 ppb77,085
Magoffin County Water DistrictSalyersville, KY8 of 891.2 ppb10,294
City of Temple*Temple, TX32 of 3288.8 ppb69,180
Marshall*Marshall, MO16 of 1686.2 ppb13,065
City of Port Lavaca*Port Lavaca, TX16 of 1685.2 ppb12,248
Ardmore*Ardmore, OK16 of 1684.5 ppb24,283
Southern Water & Sewer District*Mcdowell, KY16 of 1684.4 ppb22,480
Washington Water Authority WWAFarmington, AR16 of 1684.1 ppb15,734
Corpus Christi Naval Air StationCorpus Christi, TX8 of 883.9 ppb10,464
Martin County Water District #1Inez, KY16 of 1683.7 ppb10,843
City of Winter SpringsWinter Springs, FL16 of 1683.1 ppb35,996
Okmulgee*Okmulgee, OK16 of 1682.0 ppb13,495
Suisun-Solano Water AuthorityVacaville, CA1 of 180.0 ppb28,856
Oneida Water and Sewer Comm.*Oneida, TN16 of 1679.5 ppb11,233
City of San Benito*San Benito, TX15 of 1579.0 ppb24,250
Greenup Water System*Greenup, KY16 of 1677.4 ppb12,193
Authority of Boro of Charleroi*Charleroi, PA16 of 1677.1 ppb26,330
CoalingaCoalinga, CA33 of 3376.8 ppb19,362
Wagoner County Rwd #4Broken Arrow, OK20 of 2076.8 ppb25,792

* This water utility supplies finished drinking water to at least one other water utility. The purchasing utility is not required to test for or report Total trihalomethanes (TTHMs), but it likely has the contaminant in its water supply.

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