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EWG's Tap Water Database — 2021 UPDATE

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Total trihalomethanes (TTHMs)

Sandwich Water District

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

 

180

Samples

0

Samples exceeding legal limit (MCL)

124

Samples exceeding
health guidelines

Testing results - average by year

 
YearAverage resultSamples takenDetectionsRange of results
20141.19 ppb550.770 ppb - 1.43 ppb
20152.24 ppb3634ND - 5.60 ppb
20162.32 ppb3725ND - 6.70 ppb
20171.90 ppb3624ND - 6.70 ppb
20182.24 ppb2921ND - 7.60 ppb
20190.975 ppb3715ND - 5.09 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
2014-01-071.39 ppb
2014-04-151.01 ppb
2014-04-280.770 ppb
2014-07-251.35 ppb
2014-10-151.43 ppb
2015-01-093.20 ppb
2015-01-093.20 ppb
2015-01-093.20 ppb
2015-01-093.20 ppb
2015-01-090.820 ppb
2015-01-090.820 ppb
2015-01-091.30 ppb
2015-01-091.30 ppb
2015-02-261.35 ppb
2015-04-014.40 ppb
2015-04-014.40 ppb
2015-04-013.50 ppb
2015-04-013.50 ppb
2015-04-01ND
2015-04-01ND
2015-04-010.810 ppb
2015-04-010.810 ppb
2015-04-061.10 ppb
2015-04-070.620 ppb
2015-07-015.60 ppb
2015-07-015.60 ppb
2015-07-013.70 ppb
2015-07-013.70 ppb
2015-07-010.950 ppb
2015-07-010.950 ppb
2015-07-010.920 ppb
2015-07-010.920 ppb
2015-07-171.23 ppb
2015-10-013.90 ppb
2015-10-013.90 ppb
2015-10-013.80 ppb
2015-10-013.80 ppb
2015-10-010.710 ppb
2015-10-010.710 ppb
2015-10-011.40 ppb
2015-10-011.40 ppb
2016-01-044.90 ppb
2016-01-044.90 ppb
2016-01-043.40 ppb
2016-01-043.40 ppb
2016-01-04ND
2016-01-04ND
2016-01-04ND
2016-01-04ND
2016-01-191.07 ppb
2016-02-161.23 ppb
2016-04-063.40 ppb
2016-04-063.40 ppb
2016-04-063.70 ppb
2016-04-063.70 ppb
2016-04-060.550 ppb
2016-04-060.550 ppb
2016-04-060.820 ppb
2016-04-060.820 ppb
2016-06-091.16 ppb
2016-07-016.10 ppb
2016-07-016.10 ppb
2016-07-016.70 ppb
2016-07-016.70 ppb
2016-07-01ND
2016-07-01ND
2016-07-01ND
2016-07-01ND
2016-09-201.21 ppb
2016-10-045.80 ppb
2016-10-045.80 ppb
2016-10-044.50 ppb
2016-10-044.50 ppb
2016-10-04ND
2016-10-04ND
2016-10-04ND
2016-10-04ND
2016-12-071.36 ppb
2017-01-033.20 ppb
2017-01-033.20 ppb
2017-01-033.50 ppb
2017-01-033.50 ppb
2017-01-03ND
2017-01-03ND
2017-01-03ND
2017-01-03ND
2017-03-011.85 ppb
2017-04-034.40 ppb
2017-04-034.40 ppb
2017-04-031.90 ppb
2017-04-031.90 ppb
2017-04-03ND
2017-04-03ND
2017-04-03ND
2017-04-03ND
2017-05-081.42 ppb
2017-05-090.807 ppb
2017-07-056.70 ppb
2017-07-056.70 ppb
2017-07-052.80 ppb
2017-07-052.80 ppb
2017-07-05ND
2017-07-05ND
2017-07-05ND
2017-07-05ND
2017-10-034.25 ppb
2017-10-034.25 ppb
2017-10-033.14 ppb
2017-10-033.14 ppb
2017-10-030.860 ppb
2017-10-030.860 ppb
2017-10-030.630 ppb
2017-10-030.630 ppb
2017-12-131.52 ppb
2018-01-022.30 ppb
2018-01-022.30 ppb
2018-01-022.80 ppb
2018-01-022.80 ppb
2018-01-020.630 ppb
2018-01-020.630 ppb
2018-01-02ND
2018-01-02ND
2018-01-221.50 ppb
2018-05-020.812 ppb
2018-05-070.633 ppb
2018-07-037.20 ppb
2018-07-037.20 ppb
2018-07-033.10 ppb
2018-07-033.10 ppb
2018-07-03ND
2018-07-03ND
2018-07-03ND
2018-07-03ND
2018-07-161.16 ppb
2018-10-017.60 ppb
2018-10-017.60 ppb
2018-10-015.50 ppb
2018-10-015.50 ppb
2018-10-010.700 ppb
2018-10-010.700 ppb
2018-10-01ND
2018-10-01ND
2018-10-031.27 ppb
2019-01-033.30 ppb
2019-01-033.30 ppb
2019-01-032.30 ppb
2019-01-032.30 ppb
2019-01-03ND
2019-01-03ND
2019-01-03ND
2019-01-03ND
2019-02-131.14 ppb
2019-04-01ND
2019-04-01ND
2019-04-022.82 ppb
2019-04-022.82 ppb
2019-04-021.87 ppb
2019-04-021.87 ppb
2019-04-02ND
2019-04-02ND
2019-05-220.700 ppb
2019-05-230.874 ppb
2019-07-09ND
2019-07-09ND
2019-07-09ND
2019-07-09ND
2019-07-09ND
2019-07-09ND
2019-07-09ND
2019-07-09ND
2019-07-221.09 ppb
2019-10-03ND
2019-10-03ND
2019-10-035.09 ppb
2019-10-035.09 ppb
2019-10-03ND
2019-10-03ND
2019-10-03ND
2019-10-03ND
2019-12-031.51 ppb