EWG's Tap Water Database




Bromoform, one of the total trihalomethanes (TTHMs), is formed when chlorine or other disinfectants are used to treat drinking water. Bromoform 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
20102.92 ppb442.28 ppb - 4.63 ppb
20112.46 ppb550.900 ppb - 3.83 ppb
20123.76 ppb442.94 ppb - 4.71 ppb
20132.47 ppb771.95 ppb - 3.08 ppb
20142.14 ppb17171.44 ppb - 2.83 ppb
20152.90 ppb16161.71 ppb - 4.49 ppb

ppb = parts per billion.

State and national drinking water standards and health guidelines

Health Guideline 0.5 ppb

The health guideline of 0.5 ppb for bromoform 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.

EPA Maximum Contaminant
Level Goal (MCLG)0 ppb

A non-enforceable federal health guideline. For cancer-causing chemicals, these health goals are typically set to zero.

ppb = parts per billion.

All test results

Date Lab ID Result
2010-01-15AB112914.63 ppb
2010-04-20AB163592.30 ppb
2010-07-20AB276372.28 ppb
2010-10-26AB351562.45 ppb
2011-01-06AB392253.83 ppb
2011-03-07AB430620.900 ppb
2011-04-20AB442052.38 ppb
2011-07-12AB513461.60 ppb
2011-10-20AB599483.57 ppb
2012-01-24AB636503.83 ppb
2012-04-25AB690923.56 ppb
2012-08-02AB780732.94 ppb
2012-10-18AB848104.71 ppb
2013-02-12AB897962.85 ppb
2013-04-23AB948653.08 ppb
2013-07-16AC041892.29 ppb
2013-10-15AC125782.28 ppb
2013-10-15AC125791.95 ppb
2013-10-15AC125802.74 ppb
2013-10-15AC125812.08 ppb
2014-01-14AC166222.08 ppb
2014-01-14AC166212.58 ppb
2014-01-14AC166202.02 ppb
2014-01-14AC166192.83 ppb
2014-03-12AC206391.44 ppb
2014-04-08AC215262.57 ppb
2014-04-08AC215271.99 ppb
2014-04-08AC215282.78 ppb
2014-04-08AC215292.17 ppb
2014-07-23AC305231.99 ppb
2014-07-23AC305222.12 ppb
2014-07-23AC305242.51 ppb
2014-07-23AC305252.00 ppb
2014-10-15AC375921.69 ppb
2014-10-15AC375932.00 ppb
2014-10-15AC375941.72 ppb
2014-10-15AC375951.86 ppb
2015-01-14AC403193.20 ppb
2015-01-14AC403183.72 ppb
2015-01-14AC403173.20 ppb
2015-01-14AC403164.13 ppb
2015-04-21AC450031.86 ppb
2015-04-21AC450022.04 ppb
2015-04-21AC450011.71 ppb
2015-04-21AC450002.28 ppb
2015-07-14AC542071.82 ppb
2015-07-14AC542052.34 ppb
2015-07-14AC542061.94 ppb
2015-07-14AC542081.98 ppb
2015-10-14AC611594.24 ppb
2015-10-14AC611623.74 ppb
2015-10-14AC611614.49 ppb
2015-10-14AC611603.70 ppb