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EWG's Tap Water Database — 2019 UPDATE

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Total trihalomethanes (TTHMs)

United Water Pennsylvania

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.

 

220

Samples

29

Samples exceeding legal limit (MCL)

219

Samples exceeding
health guidelines

Testing results - average by year

 
YearAverage resultSamples takenDetectionsRange of results
201247.3 ppb3534ND - 130.0 ppb
201346.4 ppb323211.2 ppb - 113.0 ppb
201449.7 ppb33337.90 ppb - 95.5 ppb
201551.1 ppb404010.4 ppb - 118.0 ppb
201656.0 ppb40408.80 ppb - 108.0 ppb
201753.7 ppb404011.7 ppb - 113.0 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
2012-02-08441 CAMERON18.5 ppb
2012-02-08CD EAST ADMN14.3 ppb
2012-02-08DAUPHIN VOTE23.4 ppb
2012-02-08HUMMELSTOWN11.3 ppb
2012-02-08SHERATON HOT14.7 ppb
2012-02-08OLMSTEAD PLA5.80 ppb
2012-02-0841 CEYMORE S17.2 ppb
2012-02-08118 PLEASANT19.8 ppb
2012-02-08SCHUYKILL ST25.6 ppb
2012-05-08441 CAMERON58.8 ppb
2012-05-08CD ADMIN BLD55.4 ppb
2012-05-08DAUPHIN VO T34.7 ppb
2012-05-08HUMMELSTOWN35.6 ppb
2012-05-08SHERATON HOT47.3 ppb
2012-05-08OLMSTEAD PLAND
2012-05-0841 CEYMORE S54.9 ppb
2012-05-08118 PLEASANT58.9 ppb
2012-05-08SCHUYKILL ST55.4 ppb
2012-08-09441 CAMERON65.2 ppb
2012-08-09CD ADMIN BLD77.4 ppb
2012-08-09DAUPHIN VOTE48.6 ppb
2012-08-09HUMMELSTOWN90.0 ppb
2012-08-09SHERATON HOT130.0 ppb
2012-08-09OLMSTED PLAZ10.5 ppb
2012-08-0941 CEYMORE S127.0 ppb
2012-08-09118 PLEASANT110.0 ppb
2012-08-09SCHUYKILL ST56.8 ppb
2012-11-08BUCKINGHAM R41.7 ppb
2012-11-08L&N BEVERAGE45.8 ppb
2012-11-08CEYMORE ST55.7 ppb
2012-11-08FOREST HILL66.4 ppb
2012-11-08DEVON MANOR44.3 ppb
2012-11-08EDGEMONT FIR40.6 ppb
2012-11-08SHERTON LIND63.8 ppb
2012-11-08OBERLIN BOOS30.6 ppb
2013-02-11BUCKINGHAM R15.8 ppb
2013-02-11L&N BEVERAGE17.2 ppb
2013-02-11CEYMORE ST17.9 ppb
2013-02-11FOREST HILL41.4 ppb
2013-02-11DEVON MANOR21.7 ppb
2013-02-11EDGEMONT FIR15.0 ppb
2013-02-11SHERTON LIND21.1 ppb
2013-02-11OBERLIN BOOS11.2 ppb
2013-05-08BUCKINGHAM R45.4 ppb
2013-05-08L&N BEVERAGE48.1 ppb
2013-05-08CEYMORE ST46.0 ppb
2013-05-08FOREST HILLS60.8 ppb
2013-05-08DEVON MANOR54.7 ppb
2013-05-08EDGEMONT FIR53.3 ppb
2013-05-08SHERATON LIN61.0 ppb
2013-05-08OBERLIN BOOS37.1 ppb
2013-08-08BUCKINGHAM R93.3 ppb
2013-08-08L&N BEVERAGE56.5 ppb
2013-08-08CEYMORE ST74.1 ppb
2013-08-08FOREST HILLS113.0 ppb
2013-08-08DEVON MANOR73.1 ppb
2013-08-08EDGEMONT FIR86.2 ppb
2013-08-08SHERATON LIN76.6 ppb
2013-08-08OBERLIN BOOS56.4 ppb
2013-11-07BUCKINGHAM R44.7 ppb
2013-11-07L&N BEVERAGE34.4 ppb
2013-11-07CEYMORE ST45.9 ppb
2013-11-07FOREST HILLS44.9 ppb
2013-11-07DEVON MANOR23.2 ppb
2013-11-07EDGEMONT FIR29.1 ppb
2013-11-07SHERATON LIN38.7 ppb
2013-11-07OBERLIN BOOS28.2 ppb
2014-02-11107134600120.8 ppb
2014-02-11107134600212.5 ppb
2014-02-11107134600323.4 ppb
2014-02-11107134600432.6 ppb
2014-02-11107134600512.5 ppb
2014-02-1110713460069.50 ppb
2014-02-11107134600720.9 ppb
2014-02-1110713460087.90 ppb
2014-05-09200607800140.0 ppb
2014-05-09200607800246.9 ppb
2014-05-09200607800339.0 ppb
2014-05-09200607800465.0 ppb
2014-05-09200607800551.4 ppb
2014-05-09200607800652.7 ppb
2014-05-09200607800743.2 ppb
2014-05-09200607800831.7 ppb
2014-08-11202271600147.6 ppb
2014-08-11202271600287.7 ppb
2014-08-11202271600349.1 ppb
2014-08-11202271600473.6 ppb
2014-08-11202271600588.8 ppb
2014-08-11202271600651.4 ppb
2014-08-11202271600791.0 ppb
2014-08-11202271600861.5 ppb
2014-11-10203916500178.2 ppb
2014-11-10203916500251.2 ppb
2014-11-10203916500366.9 ppb
2014-11-10203916500495.5 ppb
2014-11-10203916500552.4 ppb
2014-11-10203916500654.9 ppb
2014-11-10203916500769.2 ppb
2014-11-10203916500834.9 ppb
2014-12-01204244700174.9 ppb
2015-01-051236860244.5 ppb
2015-02-091248150816.8 ppb
2015-02-091248151413.9 ppb
2015-02-091248152018.6 ppb
2015-02-091248152622.1 ppb
2015-02-091248153222.5 ppb
2015-02-091248153813.2 ppb
2015-02-091248154419.9 ppb
2015-02-091248155010.4 ppb
2015-03-091259740723.5 ppb
2015-04-011259741345.4 ppb
2015-05-111284424441.0 ppb
2015-05-111284425054.7 ppb
2015-05-111284425638.8 ppb
2015-05-111284426281.6 ppb
2015-05-111284426860.2 ppb
2015-05-111284427462.0 ppb
2015-05-111284428052.4 ppb
2015-05-111284428657.2 ppb
2015-06-0312844299101.0 ppb
2015-07-0613101922118.0 ppb
2015-08-101322807764.6 ppb
2015-08-101322808339.9 ppb
2015-08-101322808957.7 ppb
2015-08-1013228095107.0 ppb
2015-08-101322810161.9 ppb
2015-08-101322810757.5 ppb
2015-08-101322811369.2 ppb
2015-08-101322811957.9 ppb
2015-09-011322819678.4 ppb
2015-10-061347744065.7 ppb
2015-11-091359871146.2 ppb
2015-11-091359871741.6 ppb
2015-11-091359872334.6 ppb
2015-11-091359872973.0 ppb
2015-11-091359873548.9 ppb
2015-11-091359874140.6 ppb
2015-11-091359874757.6 ppb
2015-11-091359875344.6 ppb
2015-12-071371825078.4 ppb
2016-01-081383673847.9 ppb
2016-02-081395169513.7 ppb
2016-02-081395170124.0 ppb
2016-02-081395170712.5 ppb
2016-02-081395171333.3 ppb
2016-02-081395171923.7 ppb
2016-02-081395172522.1 ppb
2016-02-081395173112.1 ppb
2016-02-08139517378.80 ppb
2016-03-011395168338.5 ppb
2016-04-041406717748.1 ppb
2016-05-091436230145.3 ppb
2016-05-091436232556.8 ppb
2016-05-091436228952.1 ppb
2016-05-091436230775.7 ppb
2016-05-091436229552.7 ppb
2016-05-091436228352.0 ppb
2016-05-091436231352.9 ppb
2016-05-091436231949.7 ppb
2016-06-061436234686.3 ppb
2016-07-051469099188.9 ppb
2016-08-0814860684100.0 ppb
2016-08-081486066067.2 ppb
2016-08-081486069083.5 ppb
2016-08-081486067268.5 ppb
2016-08-081486067864.3 ppb
2016-08-081486069678.0 ppb
2016-08-0814860702108.0 ppb
2016-08-081486066663.4 ppb
2016-09-121503337699.8 ppb
2016-10-131518670355.2 ppb
2016-11-091532937864.0 ppb
2016-11-091532939066.3 ppb
2016-11-091532935473.2 ppb
2016-11-091532937284.6 ppb
2016-11-091532939655.9 ppb
2016-11-091532936058.3 ppb
2016-11-091532936669.4 ppb
2016-11-091532938439.7 ppb
2016-12-051547472444.2 ppb
2017-01-111561758635.7 ppb
2017-02-081575452513.5 ppb
2017-02-081575453720.3 ppb
2017-02-081575453115.1 ppb
2017-02-081575451025.5 ppb
2017-02-081575454920.5 ppb
2017-02-081575454318.3 ppb
2017-02-081575451612.6 ppb
2017-02-081575450411.7 ppb
2017-03-061589536140.6 ppb
2017-04-041604918945.2 ppb
2017-05-101621128341.6 ppb
2017-05-101621125949.3 ppb
2017-05-101621126539.0 ppb
2017-05-101621127770.1 ppb
2017-05-101621125352.5 ppb
2017-05-101621124150.8 ppb
2017-05-101621124741.5 ppb
2017-05-101621127147.9 ppb
2017-06-051637204283.7 ppb
2017-07-0616522827103.0 ppb
2017-08-101668301198.3 ppb
2017-08-101668298152.3 ppb
2017-08-1016683005108.0 ppb
2017-08-1016682993113.0 ppb
2017-08-101668299968.6 ppb
2017-08-101668296866.8 ppb
2017-08-1016682974102.0 ppb
2017-08-101668298671.1 ppb
2017-09-111683793793.4 ppb
2017-10-041683804369.8 ppb
2017-11-091712307541.3 ppb
2017-11-091712309362.8 ppb
2017-11-091712306952.4 ppb
2017-11-091712309964.2 ppb
2017-11-091712308144.4 ppb
2017-11-091712308761.3 ppb
2017-11-091712306344.0 ppb
2017-11-091712310535.9 ppb
2017-12-041712326160.8 ppb