EWG's Tap Water Database


Haloacetic acids (HAA5)


Haloacetic acids are formed when disinfectants such as chlorine are added to tap water. The group of five haloacetic acids regulated by federal standards includes monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, monobromoacetic acid and dibromoacetic acid. Read More.

Haloacetic acids are harmful during pregnancy and may increase the risk of cancer. Haloacetic acids are genotoxic, which means that they induce mutations and DNA damage. Multiple studies by the National Toxicology Program have demonstrated the cancer-causing properties of individual haloacetic acids in laboratory animals. The Department of Health and Human Services is currently considering listing di- or tri-haloacetic acids for possible inclusion in its comprehensive Report on Carcinogens.

Click here to read more about disinfection byproducts.





Samples exceeding legal limit (MCL)


Samples exceeding
health guidelines

Testing results - average by year

YearAverage resultSamples takenDetectionsRange of results
201020.0 ppb161613.4 ppb - 26.6 ppb
201118.5 ppb16169.70 ppb - 34.0 ppb
201222.6 ppb28285.80 ppb - 33.0 ppb
201331.3 ppb32328.10 ppb - 64.0 ppb
201423.4 ppb323210.8 ppb - 37.0 ppb
201522.0 ppb323210.9 ppb - 34.1 ppb

ppb = parts per billion.

State and national drinking water standards and health guidelines

EPA Maximum Contaminant
Level (MCL) 60 ppb

The enforceable federal standard that defines the highest level of a contaminant allowed in drinking water.

ppb = parts per billion.

All test results

Date Lab ID Result
2010-02-01AG8124420.7 ppb
2010-02-01AG8124526.6 ppb
2010-02-01AG8124622.0 ppb
2010-02-01AG8124718.6 ppb
2010-05-04AG8829626.3 ppb
2010-05-04AG8829719.4 ppb
2010-05-04AG8829818.5 ppb
2010-05-04AG8829919.1 ppb
2010-08-02AG9527223.4 ppb
2010-08-02AG9527317.2 ppb
2010-08-02AG9527422.7 ppb
2010-08-02AG9527524.5 ppb
2010-11-02AH0976918.2 ppb
2010-11-02AH0977013.9 ppb
2010-11-02AH0977113.4 ppb
2010-11-02AH0977214.8 ppb
2011-02-07AH1883725.0 ppb
2011-02-07AH1883830.0 ppb
2011-02-07AH1883931.0 ppb
2011-02-07AH1884034.0 ppb
2011-04-18AH2756529.0 ppb
2011-04-18AH2756624.0 ppb
2011-04-18AH2756722.2 ppb
2011-04-18AH2756812.0 ppb
2011-08-08AH3665615.1 ppb
2011-08-08AH366579.70 ppb
2011-08-08AH3665811.2 ppb
2011-08-08AH3665910.2 ppb
2011-12-15AH4853310.6 ppb
2011-12-15AH4853410.7 ppb
2011-12-15AH4853510.9 ppb
2011-12-15AH4853610.5 ppb
2012-02-06AH5262024.1 ppb
2012-02-06AH5262127.6 ppb
2012-02-06AH5262228.5 ppb
2012-02-06AH526235.80 ppb
2012-04-09AH5631531.0 ppb
2012-04-09AH5631629.0 ppb
2012-04-09AH5631719.6 ppb
2012-04-09AH5631833.0 ppb
2012-04-09AH5631930.0 ppb
2012-04-09AH5632032.0 ppb
2012-04-09AH5632121.0 ppb
2012-04-09AH5632225.0 ppb
2012-07-10AH6958632.3 ppb
2012-07-10AH6958730.4 ppb
2012-07-10AH6958820.4 ppb
2012-07-10AH6958928.2 ppb
2012-07-10AH6959021.8 ppb
2012-07-10AH6959118.1 ppb
2012-07-10AH6959217.4 ppb
2012-07-10AH6959321.9 ppb
2012-10-10AH8154114.2 ppb
2012-10-10AH8154216.4 ppb
2012-10-10AH8154314.0 ppb
2012-10-10AH8154419.8 ppb
2012-10-10AH8154519.4 ppb
2012-10-10AH8154621.2 ppb
2012-10-10AH8154713.3 ppb
2012-10-10AH8154817.7 ppb
2013-01-08AH871258.10 ppb
2013-01-08AH871269.30 ppb
2013-01-08AH8712713.3 ppb
2013-01-08AH8712818.8 ppb
2013-01-08AH8712917.7 ppb
2013-01-08AH8713018.8 ppb
2013-01-08AH8713113.6 ppb
2013-01-08AH8713211.6 ppb
2013-04-08AH9864138.0 ppb
2013-04-08AH9864247.2 ppb
2013-04-08AH9864326.0 ppb
2013-04-08AH9864441.1 ppb
2013-04-08AH9864530.0 ppb
2013-04-08AH9864634.0 ppb
2013-04-08AH9864723.6 ppb
2013-04-08AH9864831.0 ppb
2013-07-09AI0582647.7 ppb
2013-07-09AI0582752.7 ppb
2013-07-09AI0582847.7 ppb
2013-07-09AI0582964.0 ppb
2013-07-09AI0583052.0 ppb
2013-07-09AI0583151.3 ppb
2013-07-09AI0583241.2 ppb
2013-07-09AI0583344.2 ppb
2013-10-08AI2021219.3 ppb
2013-10-08AI2021319.4 ppb
2013-10-08AI2021421.0 ppb
2013-10-08AI2021543.0 ppb
2013-10-08AI2021634.8 ppb
2013-10-08AI2021736.7 ppb
2013-10-08AI2021819.4 ppb
2013-10-08AI2021925.6 ppb
2014-01-10AI2633325.0 ppb
2014-01-10AI2633425.0 ppb
2014-01-10AI2633527.0 ppb
2014-01-10AI2633626.0 ppb
2014-01-10AI2633732.0 ppb
2014-01-10AI2633829.0 ppb
2014-01-10AI2633918.5 ppb
2014-01-10AI2634026.0 ppb
2014-04-08AI3766925.0 ppb
2014-04-08AI3767028.0 ppb
2014-04-08AI3767121.0 ppb
2014-04-08AI3767229.0 ppb
2014-04-08AI3767337.0 ppb
2014-04-08AI3767435.0 ppb
2014-04-08AI3767517.0 ppb
2014-04-08AI3767627.0 ppb
2014-07-08AI4528425.0 ppb
2014-07-08AI4528521.0 ppb
2014-07-08AI4528619.6 ppb
2014-07-08AI4528728.0 ppb
2014-07-08AI4528820.5 ppb
2014-07-08AI4528925.0 ppb
2014-07-08AI4529016.9 ppb
2014-07-09AI4529128.0 ppb
2014-10-07AI5704515.0 ppb
2014-10-07AI5704619.1 ppb
2014-10-07AI5704720.5 ppb
2014-10-07AI5704822.2 ppb
2014-10-07AI5704916.1 ppb
2014-10-07AI5705018.5 ppb
2014-10-07AI5705110.8 ppb
2014-10-07AI5705214.3 ppb
2015-01-13AI6277422.9 ppb
2015-01-13AI6277520.0 ppb
2015-01-13AI6277621.1 ppb
2015-01-13AI6277727.0 ppb
2015-01-13AI6277823.0 ppb
2015-01-13AI6277928.0 ppb
2015-01-13AI6278019.1 ppb
2015-01-13AI6278119.6 ppb
2015-04-07AI7425918.6 ppb
2015-04-07AI7426017.7 ppb
2015-04-07AI7426127.0 ppb
2015-04-07AI7426232.0 ppb
2015-04-07AI7426326.0 ppb
2015-04-07AI7426434.1 ppb
2015-04-07AI7426518.8 ppb
2015-04-07AI7426623.0 ppb
2015-07-07AI8192421.5 ppb
2015-07-07AI8192522.5 ppb
2015-07-07AI8192613.7 ppb
2015-07-07AI8192710.9 ppb
2015-07-07AI8192816.1 ppb
2015-07-07AI8192920.3 ppb
2015-07-07AI8193033.0 ppb
2015-07-07AI8193112.8 ppb
2015-10-06AI9238726.0 ppb
2015-10-06AI9238827.1 ppb
2015-10-06AI9238915.3 ppb
2015-10-06AI9239021.9 ppb
2015-10-06AI9239127.5 ppb
2015-10-06AI9239225.8 ppb
2015-10-06AI9239314.7 ppb
2015-10-06AI9239416.1 ppb