EWG's Tap Water Database — 2021 UPDATE



Northwest Utility District-SD

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
20141.12 ppb111.12 ppb
20150.990 ppb110.990 ppb
20161.22 ppb111.22 ppb
20170.425 ppb21ND - 0.849 ppb
20180.950 ppb110.950 ppb
20191.25 ppb111.25 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 Result
2014-09-241.12 ppb
2015-10-140.990 ppb
2016-10-171.22 ppb
2017-10-170.849 ppb
2018-09-100.950 ppb
2019-09-161.25 ppb