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EWG's Tap Water Database — 2019 UPDATE

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Total trihalomethanes (TTHMs)

Combine Water Supply Corporation

NOTE: Combine Water Supply Corporation purchases water from City of Seagoville which is required to test for total trihalomethanes (tthms). Sample information shown below was taken by City of Seagoville.

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.

 

93

Samples

0

Samples exceeding legal limit (MCL)

93

Samples exceeding
health guidelines

Testing results - average by year

 
YearAverage resultSamples takenDetectionsRange of results
201212.5 ppb337.60 ppb - 19.9 ppb
201323.5 ppb4412.4 ppb - 39.9 ppb
201426.9 ppb4413.1 ppb - 58.9 ppb
201513.8 ppb4411.3 ppb - 16.9 ppb
201615.3 ppb448.38 ppb - 24.5 ppb
201711.4 ppb447.64 ppb - 15.6 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

NOTE: Combine Water Supply Corporation purchases water from City of Seagoville which is required to test for total trihalomethanes (tthms). Sample information shown below was taken by City of Seagoville.

Date Lab ID Result
2012-02-21120258600212.3 ppb
2012-05-16120565100412.2 ppb
2012-05-16120565100312.8 ppb
2012-05-16120565100211.4 ppb
2012-05-16120565100112.2 ppb
2012-07-31120810000412.2 ppb
2012-07-31120810000112.8 ppb
2012-07-31120810000212.9 ppb
2012-07-31120810000313.6 ppb
2012-10-301210A290028.10 ppb
2012-10-301210A290018.00 ppb
2012-10-301210A290037.30 ppb
2012-10-301210A290047.70 ppb
2013-02-12130241500317.1 ppb
2013-02-12130241500516.8 ppb
2013-02-12130241500415.8 ppb
2013-02-12130241500216.4 ppb
2013-04-1613045660018.30 ppb
2013-04-1613045660028.30 ppb
2013-04-1613045660038.80 ppb
2013-04-1613045660049.10 ppb
2013-07-30Q130455900611.4 ppb
2013-07-30Q130455900511.5 ppb
2013-07-30Q130455900811.7 ppb
2013-07-30Q130455900711.8 ppb
2013-10-28Q130997900814.3 ppb
2013-10-28Q130997900715.4 ppb
2013-10-28Q130997900615.3 ppb
2013-10-28Q130997900515.8 ppb
2014-03-17Q140846400115.1 ppb
2014-03-17Q140846400215.3 ppb
2014-03-17Q140846400313.7 ppb
2014-03-17Q140846400413.2 ppb
2014-05-15Q141659800414.2 ppb
2014-05-15Q141659800211.3 ppb
2014-05-15Q141659800311.9 ppb
2014-05-15Q141659800111.9 ppb
2014-09-02Q144052900117.8 ppb
2014-09-02Q144052900218.2 ppb
2014-09-02Q144052900317.1 ppb
2014-09-02Q144052900416.6 ppb
2014-10-28Q145443800222.7 ppb
2014-10-28Q145443800125.2 ppb
2014-10-28Q145443800522.6 ppb
2014-10-28Q145443800423.7 ppb
2015-01-27Q150314700515.5 ppb
2015-01-27Q150314700415.0 ppb
2015-01-27Q150314700315.0 ppb
2015-01-27Q150314700213.8 ppb
2015-05-26Q151903600412.2 ppb
2015-05-26Q15190360038.81 ppb
2015-05-26Q15190360029.15 ppb
2015-05-26Q151903600112.6 ppb
2015-08-12Q153177900114.7 ppb
2015-08-12Q153177900216.5 ppb
2015-08-12Q153177900316.3 ppb
2015-08-12Q153177900415.0 ppb
2015-10-21Q154150200116.8 ppb
2015-10-21Q154150200216.8 ppb
2015-10-21Q154150200317.0 ppb
2015-10-21Q154150200419.4 ppb
2016-01-20Q160233200412.3 ppb
2016-01-20Q160233200313.4 ppb
2016-01-20Q160233200213.5 ppb
2016-01-20Q160233200113.3 ppb
2016-04-06Q161367200113.4 ppb
2016-04-06Q161367200213.5 ppb
2016-04-06Q161367200313.4 ppb
2016-04-06Q161367200412.3 ppb
2016-07-13Q162837700418.6 ppb
2016-07-13Q162837700316.4 ppb
2016-07-13Q162837700215.1 ppb
2016-07-13Q162837700115.4 ppb
2016-10-17Q164389000112.2 ppb
2016-10-17Q164389000312.9 ppb
2016-10-17Q164389000413.1 ppb
2016-10-17Q164389000213.0 ppb
2017-01-18Q17023490017.91 ppb
2017-01-18Q17023490057.96 ppb
2017-01-18Q17023490026.95 ppb
2017-01-18Q17023490047.66 ppb
2017-04-24Q171652600210.7 ppb
2017-04-24Q171652600410.2 ppb
2017-04-24Q171652600110.4 ppb
2017-04-24Q171652600310.3 ppb
2017-07-26Q173104500311.5 ppb
2017-07-26Q173104500412.3 ppb
2017-07-26Q173104500211.3 ppb
2017-07-26Q173104500112.1 ppb
2017-10-25Q175528800212.0 ppb
2017-10-25Q175528800414.9 ppb
2017-10-25Q175528800314.6 ppb
2017-10-25Q175528800113.3 ppb