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EWG's Tap Water Database — 2021 UPDATE

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Total trihalomethanes (TTHMs)

Cedar Rapids Water Department

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

 

70

Samples

0

Samples exceeding legal limit (MCL)

44

Samples exceeding
health guidelines

Testing results - average by year

 
YearAverage resultSamples takenDetectionsRange of results
2013N/A00N/A
20142.57 ppb332.50 ppb - 2.70 ppb
20152.37 ppb332.10 ppb - 2.60 ppb
20161.51 ppb169ND - 3.40 ppb
20170.881 ppb165ND - 3.40 ppb
20182.50 ppb1614ND - 5.00 ppb
20191.84 ppb1610ND - 4.40 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
2014-03-1220397162.50 ppb
2014-09-1020810052.50 ppb
2014-12-0320969192.70 ppb
2015-03-12OE2201122.40 ppb
2015-09-16OE2941312.10 ppb
2015-12-09OE3251072.60 ppb
2016-03-08OE353815ND
2016-03-08OE353814ND
2016-03-08OE353812ND
2016-03-08OE3538132.80 ppb
2016-06-01OE383964ND
2016-06-01OE383965ND
2016-06-01OE383962ND
2016-06-01OE3839632.50 ppb
2016-09-07OE4253402.20 ppb
2016-09-07OE4253382.30 ppb
2016-09-07OE4253372.20 ppb
2016-09-07OE425339ND
2016-12-07OE4593252.60 ppb
2016-12-07OE4593272.90 ppb
2016-12-07OE4593263.30 ppb
2016-12-07OE4593283.40 ppb
2017-03-08OE4885483.30 ppb
2017-03-08OE4885512.60 ppb
2017-03-08OE4885523.40 ppb
2017-03-08OE4885502.80 ppb
2017-06-05OE521329ND
2017-06-05OE521326ND
2017-06-05OE521324ND
2017-06-05OE521327ND
2017-09-06OE561488ND
2017-09-06OE5614872.00 ppb
2017-09-06OE561485ND
2017-09-06OE561486ND
2017-12-12OE600503ND
2017-12-12OE600501ND
2017-12-12OE600502ND
2017-12-12OE600500ND
2018-03-20OE6358002.00 ppb
2018-03-20OE635799ND
2018-03-20OE6357985.00 ppb
2018-03-20OE6357962.10 ppb
2018-06-11OE6685222.50 ppb
2018-06-11OE6684992.60 ppb
2018-06-11OE6685002.30 ppb
2018-06-11OE6685033.00 ppb
2018-09-12OE7121182.10 ppb
2018-09-12OE7121164.00 ppb
2018-09-12OE7121152.10 ppb
2018-09-12OE7121142.20 ppb
2018-12-18OE7518143.70 ppb
2018-12-18OE7518163.20 ppb
2018-12-18OE751817ND
2018-12-18OE7518183.20 ppb
2019-03-05OE7773882.20 ppb
2019-03-05OE777389ND
2019-03-05OE7773902.40 ppb
2019-03-05OE7773912.50 ppb
2019-06-04OE8161922.90 ppb
2019-06-04OE8162002.50 ppb
2019-06-04OE816194ND
2019-06-04OE8161933.20 ppb
2019-09-09OE863073ND
2019-09-09OE863075ND
2019-09-09OE863074ND
2019-09-09OE8630712.00 ppb
2019-12-03OE9006803.10 ppb
2019-12-03OE9006794.20 ppb
2019-12-03OE9006784.40 ppb
2019-12-03OE900677ND