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EWG's Tap Water Database — 2019 UPDATE

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Total trihalomethanes (TTHMs)

Centerville City Water System

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.

 

89

Samples

0

Samples exceeding legal limit (MCL)

69

Samples exceeding
health guidelines

Testing results - average by year

 
YearAverage resultSamples takenDetectionsRange of results
20127.46 ppb128ND - 23.2 ppb
20137.96 ppb2119ND - 38.9 ppb
201417.3 ppb98ND - 35.7 ppb
201518.5 ppb118ND - 72.7 ppb
20169.22 ppb149ND - 57.1 ppb
201715.7 ppb2217ND - 77.2 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 Result
2012-01-10ND
2012-07-02ND
2012-07-022.00 ppb
2012-07-024.30 ppb
2012-10-01ND
2012-10-0116.6 ppb
2012-10-0116.6 ppb
2012-10-011.80 ppb
2012-10-0123.2 ppb
2012-10-01ND
2012-10-0123.2 ppb
2012-10-011.80 ppb
2013-01-0710.9 ppb
2013-01-077.30 ppb
2013-01-075.00 ppb
2013-01-070.600 ppb
2013-04-012.50 ppb
2013-04-013.20 ppb
2013-04-015.70 ppb
2013-04-012.80 ppb
2013-07-0116.6 ppb
2013-07-016.20 ppb
2013-07-01ND
2013-07-016.20 ppb
2013-07-016.20 ppb
2013-07-01ND
2013-07-011.70 ppb
2013-07-011.70 ppb
2013-07-0116.6 ppb
2013-07-0116.6 ppb
2013-07-011.70 ppb
2013-10-0138.9 ppb
2013-10-0116.7 ppb
2014-01-065.30 ppb
2014-01-062.60 ppb
2014-04-0710.2 ppb
2014-04-076.20 ppb
2014-07-0732.4 ppb
2014-07-0732.6 ppb
2014-08-10ND
2014-10-0630.7 ppb
2014-10-0635.7 ppb
2015-01-0514.3 ppb
2015-01-058.40 ppb
2015-04-062.20 ppb
2015-04-0641.9 ppb
2015-04-10ND
2015-07-0656.0 ppb
2015-07-061.80 ppb
2015-07-21ND
2015-07-22ND
2015-10-0572.7 ppb
2015-10-055.80 ppb
2016-01-1110.3 ppb
2016-01-11ND
2016-04-04ND
2016-04-0433.0 ppb
2016-06-153.70 ppb
2016-06-150.600 ppb
2016-07-0510.00 ppb
2016-07-051.10 ppb
2016-07-05ND
2016-07-05ND
2016-10-03ND
2016-10-0357.1 ppb
2016-10-035.40 ppb
2016-10-037.90 ppb
2017-01-097.60 ppb
2017-01-093.40 ppb
2017-01-095.70 ppb
2017-01-093.00 ppb
2017-01-10ND
2017-02-22ND
2017-04-03ND
2017-04-0349.7 ppb
2017-04-0349.7 ppb
2017-04-03ND
2017-04-033.70 ppb
2017-04-031.20 ppb
2017-04-031.20 ppb
2017-04-033.70 ppb
2017-07-06ND
2017-07-064.90 ppb
2017-07-0677.2 ppb
2017-07-064.70 ppb
2017-10-0227.6 ppb
2017-10-0224.7 ppb
2017-10-0226.2 ppb
2017-10-0250.8 ppb