EWG's Tap Water Database — 2021 UPDATE



Prescott, City of

Dibromochloromethane, one of the total trihalomethanes (TTHMs), is formed when chlorine or other disinfectants are used to treat drinking water. Dibromochloromethane and other disinfection byproducts increase the risk of cancer and may cause problems during pregnancy. 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
20142.50 ppb112.50 ppb
20150.760 ppb110.760 ppb
20161.30 ppb111.30 ppb
20170.725 ppb440.560 ppb - 1.000 ppb
20181.33 ppb440.910 ppb - 2.20 ppb
20190.363 ppb42ND - 0.830 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 dibromochloromethane was proposed in 2018 by the California Office of Environmental Health Hazard Assessment as a one-in-a-million lifetime risk of cancer. Values greater than one-in-a-million cancer risk level can result in increased cancer cases above one in a million people.

ppb = parts per billion

All test results

Date Lab ID Result
2014-08-191761462.50 ppb
2015-08-183903190.760 ppb
2016-08-296121521.30 ppb
2017-02-207115841.000 ppb
2017-05-087561970.740 ppb
2017-08-228249350.600 ppb
2017-11-208809580.560 ppb
2018-02-199074400.920 ppb
2018-05-219741571.30 ppb
2018-08-2010291302.20 ppb
2018-11-2610819140.910 ppb
2019-02-1811230090.830 ppb
2019-05-2011574670.620 ppb