EWG's Tap Water Database — 2019 UPDATE



Combine Water Supply Corporation

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

Chloroform, one of the total trihalomethanes (TTHMs), is formed when chlorine or other disinfectants are used to treat drinking water. Chloroform and other disinfection byproducts increase the risk of cancer and may cause problems during pregnancy. Read More.

In addition to tap water disinfection, chloroform pollution in the environment also comes from industrial discharges from pulp and paper mills, and from urban wastewater effluent. Human studies show that chloroform damages the kidneys, liver and central nervous system. In animals, chloroform causes infertility, birth defects and cancer.

Click here to read more about disinfection byproducts.





Samples exceeding legal limit (MCL)


Samples exceeding
health guidelines

Testing results - average by year

YearAverage resultSamples takenDetectionsRange of results
20123.37 ppb332.30 ppb - 5.00 ppb
20136.01 ppb442.27 ppb - 11.7 ppb
20146.18 ppb442.10 ppb - 15.8 ppb
20155.90 ppb442.40 ppb - 10.7 ppb
20167.15 ppb445.66 ppb - 9.66 ppb
20174.23 ppb443.21 ppb - 6.14 ppb

ppb = parts per billion

State and national drinking water standards and health guidelines

EWG Health Guideline 0.4 ppb

The EWG Health Guideline of 0.4 ppb for chloroform was proposed in 2018 by the California Office of Environmental Health Hazard Assessment as a one-in-a-million lifetime risk of cancer. Values greater than one-in-a-million cancer risk level can result in increased cancer cases above one in a million people.

ppb = parts per billion

All test results

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

Date Lab ID Result
2012-02-2112025860025.70 ppb
2012-05-1612056510043.20 ppb
2012-05-1612056510033.40 ppb
2012-05-1612056510023.40 ppb
2012-05-1612056510013.40 ppb
2012-07-3112081000045.00 ppb
2012-07-3112081000015.00 ppb
2012-07-3112081000025.10 ppb
2012-07-3112081000035.50 ppb
2012-10-301210A290022.60 ppb
2012-10-301210A290012.50 ppb
2012-10-301210A290032.40 ppb
2012-10-301210A290042.50 ppb
2013-02-1213024150033.10 ppb
2013-02-1213024150053.00 ppb
2013-02-1213024150043.00 ppb
2013-02-1213024150022.80 ppb
2013-04-1613045660012.70 ppb
2013-04-1613045660022.70 ppb
2013-04-1613045660033.00 ppb
2013-04-1613045660043.20 ppb
2013-07-30Q13045590064.44 ppb
2013-07-30Q13045590054.30 ppb
2013-07-30Q13045590084.62 ppb
2013-07-30Q13045590074.56 ppb
2013-10-28Q13099790082.46 ppb
2013-10-28Q13099790072.42 ppb
2013-10-28Q13099790062.39 ppb
2013-10-28Q13099790052.45 ppb
2014-03-17Q14084640012.10 ppb
2014-03-17Q14084640022.30 ppb
2014-03-17Q14084640032.10 ppb
2014-03-17Q14084640042.00 ppb
2014-05-15Q14165980043.70 ppb
2014-05-15Q14165980022.40 ppb
2014-05-15Q14165980032.80 ppb
2014-05-15Q14165980012.80 ppb
2014-09-02Q14405290015.30 ppb
2014-09-02Q14405290023.50 ppb
2014-09-02Q14405290033.40 ppb
2014-09-02Q14405290044.10 ppb
2014-10-28Q14544380025.10 ppb
2014-10-28Q14544380014.60 ppb
2014-10-28Q14544380054.00 ppb
2014-10-28Q14544380045.40 ppb
2015-01-27Q15031470052.50 ppb
2015-01-27Q15031470042.50 ppb
2015-01-27Q15031470032.70 ppb
2015-01-27Q15031470022.40 ppb
2015-05-26Q15190360049.51 ppb
2015-05-26Q15190360036.90 ppb
2015-05-26Q15190360027.09 ppb
2015-05-26Q15190360019.63 ppb
2015-08-12Q15317790018.66 ppb
2015-08-12Q15317790029.50 ppb
2015-08-12Q15317790039.43 ppb
2015-08-12Q15317790048.68 ppb
2015-10-21Q154150200111.6 ppb
2015-10-21Q154150200211.6 ppb
2015-10-21Q154150200311.1 ppb
2015-10-21Q154150200413.6 ppb
2016-01-20Q16023320047.81 ppb
2016-01-20Q16023320038.31 ppb
2016-01-20Q16023320028.43 ppb
2016-01-20Q16023320018.17 ppb
2016-04-06Q16136720017.76 ppb
2016-04-06Q16136720027.72 ppb
2016-04-06Q16136720037.79 ppb
2016-04-06Q16136720047.33 ppb
2016-07-13Q162837700410.8 ppb
2016-07-13Q16283770039.05 ppb
2016-07-13Q16283770028.05 ppb
2016-07-13Q16283770018.73 ppb
2016-10-17Q16438900017.41 ppb
2016-10-17Q16438900037.32 ppb
2016-10-17Q16438900047.53 ppb
2016-10-17Q16438900027.26 ppb
2017-01-18Q17023490013.15 ppb
2017-01-18Q17023490053.11 ppb
2017-01-18Q17023490022.72 ppb
2017-01-18Q17023490042.95 ppb
2017-04-24Q17165260025.61 ppb
2017-04-24Q17165260045.31 ppb
2017-04-24Q17165260015.51 ppb
2017-04-24Q17165260035.53 ppb
2017-07-26Q17310450036.41 ppb
2017-07-26Q17310450046.96 ppb
2017-07-26Q17310450026.05 ppb
2017-07-26Q17310450016.49 ppb
2017-10-25Q17552880023.83 ppb
2017-10-25Q17552880044.57 ppb
2017-10-25Q17552880034.21 ppb
2017-10-25Q17552880015.28 ppb