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EWG's Tap Water Database — 2021 UPDATE

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Total trihalomethanes (TTHMs)

Michigan State University

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

 

136

Samples

0

Samples exceeding legal limit (MCL)

122

Samples exceeding
health guidelines

Testing results - average by year

 
YearAverage resultSamples takenDetectionsRange of results
201410.1 ppb1916ND - 16.0 ppb
2015N/A00N/A
20162.82 ppb16160.900 ppb - 10.1 ppb
201710.7 ppb16160.900 ppb - 21.7 ppb
201811.9 ppb4134ND - 22.7 ppb
201913.5 ppb4440ND - 21.7 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
2014-03-05LLF1100914.0 ppb
2014-03-05LLF1101012.0 ppb
2014-03-05LLF1101212.0 ppb
2014-03-05LLF1101111.0 ppb
2014-06-02LLF2026816.0 ppb
2014-06-02LLF2026914.5 ppb
2014-06-02LLF2027014.8 ppb
2014-06-02LLF2027113.8 ppb
2014-09-02LLF3580110.7 ppb
2014-09-02LLF3580310.7 ppb
2014-09-02LLF3580210.8 ppb
2014-09-02LLF3580013.6 ppb
2014-10-23LLF44294ND
2014-10-23LLF44295ND
2014-10-23LLF44293ND
2014-12-03LLF481427.20 ppb
2014-12-03LLF481438.80 ppb
2014-12-03LLF481409.60 ppb
2014-12-03LLF4814113.2 ppb
2016-03-073.60 ppb
2016-03-072.40 ppb
2016-03-073.70 ppb
2016-03-073.10 ppb
2016-06-022.80 ppb
2016-06-022.00 ppb
2016-06-022.90 ppb
2016-06-022.50 ppb
2016-09-021.90 ppb
2016-09-021.90 ppb
2016-09-0610.1 ppb
2016-09-123.30 ppb
2016-12-071.80 ppb
2016-12-070.900 ppb
2016-12-071.10 ppb
2016-12-071.10 ppb
2017-03-081.30 ppb
2017-03-080.900 ppb
2017-03-082.20 ppb
2017-03-081.000 ppb
2017-06-0612.4 ppb
2017-06-0611.8 ppb
2017-06-0610.3 ppb
2017-06-0612.8 ppb
2017-09-1216.9 ppb
2017-09-1212.6 ppb
2017-09-1215.7 ppb
2017-09-1212.8 ppb
2017-12-0512.9 ppb
2017-12-0512.3 ppb
2017-12-0521.7 ppb
2017-12-0512.8 ppb
2018-01-17LLH61375ND
2018-01-17LLH61376ND
2018-03-14LLH707296.50 ppb
2018-03-14LLH7073013.7 ppb
2018-03-14LLH7072813.7 ppb
2018-03-14LLH707277.10 ppb
2018-03-14LLH707315.00 ppb
2018-03-14LLH70732ND
2018-03-1413.7 ppb
2018-03-146.50 ppb
2018-03-1413.7 ppb
2018-03-147.10 ppb
2018-06-11LLH85284ND
2018-06-11LLH8528014.0 ppb
2018-06-11LLH8528122.1 ppb
2018-06-11LLH8528217.3 ppb
2018-06-11LLH8528322.7 ppb
2018-06-1122.1 ppb
2018-06-1114.0 ppb
2018-06-1122.7 ppb
2018-06-1117.3 ppb
2018-09-04LLI0291311.0 ppb
2018-09-04LLI0291411.3 ppb
2018-09-04LLI0291120.9 ppb
2018-09-04LLI0291215.2 ppb
2018-09-0415.2 ppb
2018-09-0411.0 ppb
2018-09-0420.9 ppb
2018-09-0411.3 ppb
2018-09-05LLI03198ND
2018-10-23LLI12549ND
2018-12-04LLI1763310.5 ppb
2018-12-04LLI1763418.7 ppb
2018-12-04LLI1763619.8 ppb
2018-12-04LLI1763513.0 ppb
2018-12-0413.0 ppb
2018-12-0410.5 ppb
2018-12-0418.7 ppb
2018-12-06LLI18257ND
2018-12-14LLI1942514.5 ppb
2018-12-1414.5 ppb
2019-03-07LLI28375ND
2019-03-08LLI2852312.5 ppb
2019-03-08LLI2852415.6 ppb
2019-03-08LLI2852512.5 ppb
2019-03-08LLI2852611.1 ppb
2019-03-0812.5 ppb
2019-03-0811.1 ppb
2019-03-0815.6 ppb
2019-03-0812.5 ppb
2019-06-04LLI4069519.4 ppb
2019-06-04LLI4069619.9 ppb
2019-06-04LLI4069316.0 ppb
2019-06-04LLI4069418.9 ppb
2019-06-0419.4 ppb
2019-06-0416.0 ppb
2019-06-0418.9 ppb
2019-06-0419.9 ppb
2019-06-05LLI41086ND
2019-09-03LLI6100711.7 ppb
2019-09-03LLI6100812.0 ppb
2019-09-03LLI6101018.5 ppb
2019-09-03LLI6100912.8 ppb
2019-09-0312.8 ppb
2019-09-0311.7 ppb
2019-09-0318.5 ppb
2019-09-0312.0 ppb
2019-11-20LLI78249ND
2019-12-03LLI8076814.0 ppb
2019-12-03LLI8076515.2 ppb
2019-12-03LLI8076721.7 ppb
2019-12-03LLI8076614.5 ppb
2019-12-0314.5 ppb
2019-12-0315.2 ppb
2019-12-0321.7 ppb
2019-12-0314.0 ppb
2019-12-12LLI8310111.3 ppb
2019-12-12LLI8310213.8 ppb
2019-12-12LLI8310412.4 ppb
2019-12-12LLI8310314.1 ppb
2019-12-1213.8 ppb
2019-12-1212.4 ppb
2019-12-1214.1 ppb
2019-12-1211.3 ppb
2019-12-23LLI85472ND