EWG's Tap Water Database — 2021 UPDATE


Haloacetic acids (HAA5)

Oakland Psd Golden Key Acres

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
201424.3 ppb442.78 ppb - 67.6 ppb
201514.2 ppb6610.5 ppb - 25.2 ppb
201616.5 ppb3311.9 ppb - 19.7 ppb
201725.0 ppb4417.8 ppb - 33.2 ppb
201820.3 ppb4412.0 ppb - 26.0 ppb
201921.4 ppb4417.9 ppb - 26.3 ppb

ppb = parts per billion

State and national drinking water standards and health guidelines

EWG Health Guideline 0.1 ppb

The EWG Health Guideline of 0.1 ppb for the group of five haloacetic acids, or HAA5, was defined in a peer-reviewed scientific study by EWG and represents a one-in-a-million lifetime cancer risk level. This health guideline protects against cancer.

EPA Maximum Contaminant
Level (MCL) 60 ppb

The legal limit for the group of five haloacetic acids (HAA5), 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 and harm to the developing fetus due to exposure to haloacetic acids.

ppb = parts per billion

All test results

Date Lab ID Result
2014-04-04S2DBP_1404765-018.61 ppb
2014-07-07S2DBP_1407653-0167.6 ppb
2014-08-14S2DBP_1408I29-012.78 ppb
2014-10-15S2DBP_1410J63-0118.2 ppb
2015-01-06S2DBP_1501432-0311.5 ppb
2015-01-06S2DBP_1501432-0212.1 ppb
2015-01-06S2DBP_1501432-0111.9 ppb
2015-04-14S2DBP_1504K17-0114.2 ppb
2015-07-13S2DBP_1507F22-0125.2 ppb
2015-10-131510G42-01A10.5 ppb
2016-04-1116041140-02A11.9 ppb
2016-07-1216071213-02A19.7 ppb
2016-10-0416100438-01A17.9 ppb
2017-01-1917012084-01A17.8 ppb
2017-04-1017041137-01A19.7 ppb
2017-07-1717071949-01A29.2 ppb
2017-10-0517100826-02A33.2 ppb
2018-01-101801158-01A26.0 ppb
2018-04-1818042625-01A12.0 ppb
2018-07-1618072221-02A24.1 ppb
2018-10-2318102970-02A19.0 ppb
2019-01-0719010927-01A26.3 ppb
2019-04-1719042255-01A21.2 ppb
2019-07-1719072297-02A20.0 ppb
2019-10-2873604800117.9 ppb