Menu

EWG's Tap Water Database — 2021 UPDATE

Donate

Total trihalomethanes (TTHMs)

Quail Valley Utility 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

 

96

Samples

0

Samples exceeding legal limit (MCL)

24

Samples exceeding
health guidelines

Testing results - average by year

 
YearAverage resultSamples takenDetectionsRange of results
2013N/A00N/A
20142.10 ppb166ND - 17.7 ppb
20152.99 ppb164ND - 20.0 ppb
20161.41 ppb165ND - 10.9 ppb
20170.656 ppb163ND - 8.40 ppb
20180.206 ppb163ND - 1.20 ppb
20190.356 ppb163ND - 2.20 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
2014-02-20AC438441.10 ppb
2014-02-20AC438381.000 ppb
2014-02-20AC43837ND
2014-02-20AC43834ND
2014-05-21AC54971ND
2014-05-21AC54942ND
2014-05-21AC54938ND
2014-05-21AC549444.40 ppb
2014-08-05AC62206ND
2014-08-05AC621888.30 ppb
2014-08-05AC62207ND
2014-08-05AC621831.10 ppb
2014-10-28AC70777ND
2014-10-28AC70770ND
2014-10-28AC70773ND
2014-10-28AC7076617.7 ppb
2015-02-10AC79887ND
2015-02-10AC79889ND
2015-02-10AC79911ND
2015-02-10AC798887.90 ppb
2015-05-13AC917979.40 ppb
2015-05-13AC91791ND
2015-05-13AC91793ND
2015-05-13AC91795ND
2015-09-24AD08428ND
2015-09-24AD08431ND
2015-09-24AD08432ND
2015-09-24AD0842720.0 ppb
2015-12-10AD16487ND
2015-12-10AD16489ND
2015-12-10AD16490ND
2015-12-10AD1648410.6 ppb
2016-02-18AD24280ND
2016-02-18AD242758.30 ppb
2016-02-18AD24279ND
2016-02-18AD24278ND
2016-04-26AD341761.000 ppb
2016-04-26AD34174ND
2016-04-26AD34184ND
2016-04-26AD3417310.9 ppb
2016-09-22AD50658ND
2016-09-22AD506491.20 ppb
2016-09-22AD50654ND
2016-09-22AD50655ND
2016-10-19AD53752ND
2016-10-19AD53754ND
2016-10-19AD537511.10 ppb
2016-10-19AD53753ND
2017-01-18AD65341ND
2017-01-18AD65340ND
2017-01-18AD65342ND
2017-01-18AD65343ND
2017-04-12AD79420ND
2017-04-12AD794181.10 ppb
2017-04-12AD79416ND
2017-04-12AD79419ND
2017-08-02AD91806ND
2017-08-02AD918048.40 ppb
2017-08-02AD91807ND
2017-08-02AD91805ND
2017-10-11AE00353ND
2017-10-11AE003311.000 ppb
2017-10-11AE00354ND
2017-10-11AE00329ND
2018-02-28AE16006ND
2018-02-28AE159841.000 ppb
2018-02-28AE15983ND
2018-02-28AE16012ND
2018-05-29AE27853ND
2018-05-29AE27869ND
2018-05-29AE27858ND
2018-05-29AE27868ND
2018-07-24AE34300ND
2018-07-24AE34297ND
2018-07-24AE34306ND
2018-07-24AE34296ND
2018-10-04AE426871.20 ppb
2018-10-04AE426891.10 ppb
2018-10-04AE42690ND
2018-10-04AE42686ND
2019-01-30AE52151ND
2019-01-30AE52156ND
2019-01-30AE52152ND
2019-01-30AE52153ND
2019-04-18AE62928ND
2019-04-18AE629262.20 ppb
2019-04-18AE62929ND
2019-04-18AE62930ND
2019-08-12AE779772.20 ppb
2019-08-12AE77978ND
2019-08-12AE77976ND
2019-08-12AE77980ND
2019-10-16AE86755ND
2019-10-16AE867541.30 ppb
2019-10-16AE86753ND
2019-10-16AE86749ND