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EWG's Tap Water Database — 2021 UPDATE

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Total trihalomethanes (TTHMs)

City of Houston Utility District 5 - Kingwood

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.

The health guideline of 0.15 parts per billion, or ppb, for the group of four trihalomethanes, or THM4/TTHM, was defined in a peer-reviewed scientific study by EWG and represents a one-in-one-million lifetime cancer risk level.

Click here to read more about disinfection byproducts.

MORE ABOUT THIS CONTAMINANT

 

96

Samples

0

Samples exceeding legal limit (MCL)

22

Samples exceeding
health guidelines

Testing results - average by year

 
YearAverage resultSamples takenDetectionsRange of results
2013N/A00N/A
20141.84 ppb164ND - 13.1 ppb
20151.15 ppb163ND - 13.8 ppb
20160.681 ppb162ND - 5.80 ppb
20171.71 ppb164ND - 14.3 ppb
20181.54 ppb164ND - 9.60 ppb
20192.07 ppb165ND - 15.2 ppb

ppb = parts per billion

State and national drinking water standards and health guidelines

EWG Health Guideline 0.15 ppb

The health guideline of 0.15 parts per billion, or ppb, for the group of four trihalomethanes, or THM4/TTHM, was defined in a peer-reviewed scientific study by EWG and represents a one-in-one-million lifetime cancer risk level.

EPA Maximum Contaminant
Level (MCL) 80 ppb

The legal limit for the group of four trihalomethanes, established in 1998, was based on the need for residual disinfectant levels in water served to customers and the cost of treatment. This limit does not fully protect against the risk of cancer due to exposure to trihalomethanes.

ppb = parts per billion

All test results

Date Lab ID Result
2014-03-19AC47692ND
2014-03-19AC47696ND
2014-03-19AC476943.50 ppb
2014-03-19AC47693ND
2014-05-30AC55588ND
2014-05-30AC55653ND
2014-05-30AC5559013.1 ppb
2014-05-30AC55620ND
2014-08-15AC641578.10 ppb
2014-08-15AC64159ND
2014-08-15AC64155ND
2014-08-15AC64127ND
2014-10-28AC70769ND
2014-10-28AC70776ND
2014-10-28AC707684.70 ppb
2014-10-28AC70783ND
2015-01-16AC7662113.8 ppb
2015-01-16AC76626ND
2015-01-16AC76625ND
2015-01-16AC76619ND
2015-06-08AC94884ND
2015-06-08AC94888ND
2015-06-08AC94885ND
2015-06-08AC94856ND
2015-07-31AD02040ND
2015-07-31AD02043ND
2015-07-31AD020183.40 ppb
2015-07-31AD02036ND
2015-10-14AD10596ND
2015-10-14AD10595ND
2015-10-14AD105931.20 ppb
2015-10-14AD10594ND
2016-01-13AD17836ND
2016-01-13AD17834ND
2016-01-13AD17828ND
2016-01-13AD17830ND
2016-04-05AD31802ND
2016-04-05AD31815ND
2016-04-05AD318165.10 ppb
2016-04-05AD31820ND
2016-07-07AD43303ND
2016-07-07AD43313ND
2016-07-07AD43310ND
2016-07-07AD43302ND
2016-11-22AD59020ND
2016-11-22AD59011ND
2016-11-22AD59019ND
2016-11-22AD590125.80 ppb
2017-01-11AD64308ND
2017-01-11AD64309ND
2017-01-11AD643134.60 ppb
2017-01-11AD64312ND
2017-04-27AD81468ND
2017-04-27AD81463ND
2017-04-27AD814652.80 ppb
2017-04-27AD81467ND
2017-07-27AD910845.60 ppb
2017-07-27AD91085ND
2017-07-27AD91052ND
2017-07-27AD91051ND
2017-10-13AE00783ND
2017-10-13AE00770ND
2017-10-13AE0078514.3 ppb
2017-10-13AE00786ND
2018-01-31AE11820ND
2018-01-31AE11860ND
2018-01-31AE118573.90 ppb
2018-01-31AE11859ND
2018-04-16AE22494ND
2018-04-16AE224939.60 ppb
2018-04-16AE22495ND
2018-04-16AE22492ND
2018-07-30AE34886ND
2018-07-30AE34882ND
2018-07-30AE348855.00 ppb
2018-07-30AE34888ND
2018-10-19AE44095ND
2018-10-19AE44096ND
2018-10-19AE440946.20 ppb
2018-10-19AE44093ND
2019-01-22AE506783.90 ppb
2019-01-22AE50662ND
2019-01-22AE506612.90 ppb
2019-01-22AE50676ND
2019-04-11AE61992ND
2019-04-11AE61991ND
2019-04-11AE619905.20 ppb
2019-04-11AE61993ND
2019-07-22AE75291ND
2019-07-22AE75269ND
2019-07-22AE752575.90 ppb
2019-07-22AE75258ND
2019-10-11AE86454ND
2019-10-11AE86448ND
2019-10-11AE86445ND
2019-10-11AE8645015.2 ppb