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EWG's Tap Water Database — 2019 UPDATE

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Total trihalomethanes (TTHMs)

Sugarmill Woods SD

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.

 

30

Samples

0

Samples exceeding legal limit (MCL)

25

Samples exceeding
health guidelines

Testing results - average by year

 
YearAverage resultSamples takenDetectionsRange of results
20120.300 ppb220.300 ppb
20131.42 ppb660.700 ppb - 2.20 ppb
20141.76 ppb12120.600 ppb - 3.00 ppb
2015ND20ND
20160.325 ppb43ND - 0.700 ppb
20170.400 ppb42ND - 0.960 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
2012-08-230.300 ppb
2012-08-230.300 ppb
2013-08-140.800 ppb
2013-08-140.700 ppb
2013-10-231.90 ppb
2013-10-231.60 ppb
2013-10-232.20 ppb
2013-10-231.30 ppb
2014-01-231.90 ppb
2014-01-231.50 ppb
2014-01-232.10 ppb
2014-01-231.60 ppb
2014-04-092.00 ppb
2014-04-092.50 ppb
2014-04-092.30 ppb
2014-04-092.10 ppb
2014-07-240.700 ppb
2014-07-240.800 ppb
2014-07-240.600 ppb
2014-07-243.00 ppb
2015-07-08ND
2015-07-08ND
2016-05-030.300 ppb
2016-05-03ND
2016-07-260.300 ppb
2016-07-260.700 ppb
2017-05-230.960 ppb
2017-05-230.640 ppb
2017-07-16ND
2017-07-16ND