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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

25,084

utilities detected

281 million

people served

49

states over health guideline

24,241

utilities over health guideline

275 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 0.8 ppb

The health guideline of 0.8 ppb for trihalomethanes was defined by the California Office of Environmental Health Hazard Assessment 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
California1,07739,335,9441,15641,596,023
Texas2,59724,820,4812,64125,049,080
New York1,13718,307,8271,17019,393,626
Florida1,40318,664,8831,46118,839,936
Illinois1,25812,631,9071,27612,671,080
Pennsylvania1,16910,352,6451,22310,388,724
Ohio98510,025,9671,05410,130,569
Massachusetts3108,965,9163199,070,690
Georgia5447,995,4985538,047,882
North Carolina7377,562,0447427,567,018
Tennessee4216,706,9174266,721,816
Virginia5136,627,9685286,636,439
Michigan5136,493,7845276,509,573
Arizona3265,799,3633475,873,353
New Jersey2575,580,2792795,617,593
Washington6385,450,7736925,582,215
Colorado5815,496,1675945,512,004
Alabama4485,291,1764675,438,456
Maryland1484,578,8911664,898,639
Missouri6044,713,6786504,793,777
Indiana5514,647,4875604,686,929
Kentucky3744,602,7393754,603,779
Louisiana7224,418,0987454,471,445
Minnesota5043,784,0675554,027,592
Wisconsin4043,752,5704203,777,987
Oregon3403,635,8053453,677,435
South Carolina3073,486,3813103,523,481
Oklahoma8323,468,9668393,476,352
Arkansas5523,045,6195613,065,849
Kansas6482,693,2746772,755,347
Connecticut2052,654,0772112,656,273
Nevada732,527,044792,545,561
Iowa5592,390,0265592,390,026
New Mexico2481,673,1992641,689,084
Utah281,510,766281,510,766
West Virginia3791,460,5383831,489,766
Hawaii671,097,643741,345,025
Mississippi2171,009,0102171,009,010
Rhode Island44975,52644975,526
Delaware88936,08491941,034
Idaho131815,383135871,645
District Of Columbia4664,5724664,572
South Dakota242656,595242656,595
New Hampshire116578,701130618,784
North Dakota263593,278267612,227
Alaska138585,244141585,732
Montana174489,320180548,866
Maine76515,99177516,224
Vermont158434,659163436,519
Wyoming131387,540137398,526
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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, LA1 of 1230.0 ppb8,469
Wards Chapel Water SystemFarmerville, LA1 of 1228.4 ppb1,350
Vaquero FarmsFirebaugh, CA4 of 4215.0 ppb70
Pleasant Hills-crossroads Water SystemsJoyce, LA1 of 1210.9 ppb840
Village of Calvin Water SystemCalvin, LA1 of 1210.8 ppb591
Sardis Water SystemFarmerville, LA8 of 8205.3 ppb1,404
Mccurtain County Rural Water District #6 (kiamichi)Smithville, OK1 of 1198.7 ppb2,000
Vixen Water System EastWest Monroe, LA2 of 2197.0 ppb486
Fcsa #49/ Five PointsFresno, CA3 of 3196.7 ppb122
Winebrook Hills Water DistrictNewcomb, NY4 of 4194.0 ppb250
Village of Georgetown Water SupplyGeorgetown, LA4 of 4193.2 ppb302
Holmesville Water System*Downsville, LA5 of 5191.0 ppb1,845
Point Wilhite Ws*Downsville, LA10 of 10189.0 ppb1,950
Village of Surfside BeachFreeport, TX2 of 2188.5 ppb3,477
Vixen Water System WestWest Monroe, LA5 of 5187.2 ppb288
Jones Mcginty Water System*Jones, LA7 of 7185.7 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, LA4 of 4180.0 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, LA10 of 10171.5 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
Joyce Water SupplyCovington, LA4 of 4168.8 ppb474

* 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
Lemoore Naval Air StationNas Lemoore, CA20 of 20104.5 ppb11,500
City of AvenalAvenal, CA1 of 1101.0 ppb16,236
Orange County WCID 1Vidor, TX16 of 1694.1 ppb17,681
City of Havre De Grace*Havre De Grace, MD1 of 194.0 ppb14,000
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
City of LemooreLemoore, CA15 of 1788.6 ppb24,945
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
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
New Brunswick Water Department*New Brunswick, NJ1 of 177.0 ppb55,000
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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