EWG's Tap Water Database — 2019 UPDATE



York Water Company

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
201221.7 ppb25258.60 ppb - 36.0 ppb
201317.5 ppb28286.55 ppb - 57.0 ppb
201415.8 ppb16166.60 ppb - 24.4 ppb
201518.9 ppb16167.13 ppb - 28.4 ppb
201621.7 ppb20209.80 ppb - 34.6 ppb
201723.7 ppb20207.70 ppb - 44.5 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

Date Lab ID Result
2012-02-09CHAZS E. PRO8.60 ppb
2012-05-07CHAZS, E PRO13.4 ppb
2012-05-07STEWARTSTOWN12.9 ppb
2012-05-07YORKHANA TUR16.2 ppb
2012-05-07HOKE MILL16.1 ppb
2012-05-07W MANCESTER15.2 ppb
2012-05-07N YORK PUMPH16.6 ppb
2012-05-07MT ZION PUMP15.6 ppb
2012-05-07LOGANVILLE P13.3 ppb
2012-08-07CHAZS E. PRO35.2 ppb
2012-08-07STEWARTSTOWN35.9 ppb
2012-08-07YORKANA TURK31.7 ppb
2012-08-07HOKE MILL AB35.3 ppb
2012-08-07W. MANCHESTE27.1 ppb
2012-08-07N. YORK PUMP36.0 ppb
2012-08-07MT ZION PUMP34.8 ppb
2012-08-07LOGANVILLE P25.7 ppb
2012-11-07CHAZS E PROS24.7 ppb
2012-11-07STEWARTSTOWN21.6 ppb
2012-11-07YORKANA TURK20.7 ppb
2012-11-07HOKE MILL AB21.6 ppb
2012-11-07W MANCHESTER15.4 ppb
2012-11-07N YORK PUMPH16.8 ppb
2012-11-07MT ZION PUMP18.0 ppb
2012-11-07LOGANVILLE P14.9 ppb
2013-02-07HOKE MILL AB10.1 ppb
2013-02-07W MANCHESTER6.98 ppb
2013-02-08CHAZS E PROS10.8 ppb
2013-02-08YORKANA TURK8.41 ppb
2013-02-08N YORK PUMPH6.75 ppb
2013-02-08MT ZION PUMP6.74 ppb
2013-02-08LOGANVILLE P6.55 ppb
2013-02-11STEWARTSTOWN8.81 ppb
2013-05-07CHAZS E PROS12.1 ppb
2013-05-07STEWARTSTOWN12.1 ppb
2013-05-07YORKANA TURK13.6 ppb
2013-05-08HOKE MILL12.6 ppb
2013-05-08W MANCHESTER9.54 ppb
2013-05-08N YORK PUMPH11.1 ppb
2013-05-08MT ZION PUMP11.2 ppb
2013-05-08LOGANVILLE P8.86 ppb
2013-08-07HOKE MILL29.7 ppb
2013-08-08W MANCHESTER21.9 ppb
2013-08-08N YORK PUMPH24.9 ppb
2013-08-08MT ZION PUMP25.8 ppb
2013-08-09CHAZS E PROS30.4 ppb
2013-08-09YORKANA TURK27.4 ppb
2013-08-12STEWARTSTOWN57.0 ppb
2013-08-12LOGANVILLE P35.7 ppb
2013-11-07STEWARTSTOWN22.6 ppb
2013-11-07W MANCHESTER18.3 ppb
2013-11-07LOGANVILLE P17.6 ppb
2013-11-11CHAZS E PROS22.9 ppb
2014-02-1114021711-0029.80 ppb
2014-02-1114021711-0046.60 ppb
2014-02-1214021711-00114.2 ppb
2014-02-1214021711-0038.10 ppb
2014-05-0714052045-00124.4 ppb
2014-05-0814052045-00220.5 ppb
2014-05-0814052045-00315.6 ppb
2014-05-0814052045-00415.5 ppb
2014-08-1114081341-00119.3 ppb
2014-08-1114081341-00219.6 ppb
2014-08-1114081341-00315.8 ppb
2014-08-1114081341-00415.3 ppb
2014-11-0714110761-00119.1 ppb
2014-11-0714110761-00218.6 ppb
2014-11-0714110761-00416.3 ppb
2014-11-0714110761-00314.4 ppb
2015-02-101249757810.3 ppb
2015-02-10124975907.13 ppb
2015-02-111249757212.6 ppb
2015-02-11124975847.29 ppb
2015-05-081286392118.9 ppb
2015-05-111286392720.3 ppb
2015-05-111286393318.8 ppb
2015-05-111286393917.2 ppb
2015-08-111324644127.9 ppb
2015-08-111324644725.0 ppb
2015-08-111324645322.8 ppb
2015-08-111324645920.9 ppb
2015-11-101361562828.4 ppb
2015-11-101361563425.3 ppb
2015-11-101361564019.0 ppb
2015-11-101361564621.3 ppb
2016-02-101396769014.7 ppb
2016-02-101396769613.9 ppb
2016-02-10139677029.80 ppb
2016-02-101396770811.2 ppb
2016-05-061438403313.6 ppb
2016-05-111438404423.5 ppb
2016-05-111438405015.4 ppb
2016-05-111438403818.1 ppb
2016-08-101488464428.6 ppb
2016-08-101488465431.7 ppb
2016-08-101488465925.0 ppb
2016-08-101488464927.3 ppb
2016-08-301505595229.2 ppb
2016-08-301505596024.8 ppb
2016-08-311505596634.6 ppb
2016-08-311505597224.7 ppb
2016-11-071534857624.1 ppb
2016-11-071534859422.7 ppb
2016-11-091534858224.6 ppb
2016-11-101534858816.9 ppb
2017-02-071577374911.8 ppb
2017-02-07157736987.70 ppb
2017-02-07157737378.20 ppb
2017-02-081577374312.6 ppb
2017-05-091623458620.9 ppb
2017-05-091623457536.7 ppb
2017-05-091623458024.9 ppb
2017-05-091623459126.9 ppb
2017-08-081670573344.5 ppb
2017-08-101670574540.4 ppb
2017-08-101670573926.2 ppb
2017-08-101670575131.7 ppb
2017-11-081714274529.6 ppb
2017-11-081714278721.8 ppb
2017-11-081714276919.7 ppb
2017-11-081714276319.6 ppb
2017-11-081714277521.6 ppb
2017-11-081714278120.6 ppb
2017-11-091714275125.4 ppb
2017-11-091714275723.4 ppb