EWG's Tap Water Database — 2019 UPDATE


Monochloroacetic acid

Oswego, City of

Monochloroacetic acid, one of the group of five haloacetic acids regulated by federal standards, is formed when chlorine or other disinfectants are used to treat drinking water. Haloacetic acids 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
20124.23 ppb43ND - 10.00 ppb
20135.13 ppb442.60 ppb - 6.40 ppb
20143.03 ppb442.10 ppb - 3.90 ppb
20152.83 ppb442.60 ppb - 3.30 ppb
20163.23 ppb442.10 ppb - 4.50 ppb
20172.58 ppb442.00 ppb - 4.00 ppb

ppb = parts per billion

State and national drinking water standards and health guidelines

EWG Health Guideline 53 ppb

The EWG Health Guideline of 53 ppb for monochloroacetic acid was proposed in 2020 by the California Office of Environmental Health Hazard Assessment as a public health goal, the level of a drinking water contaminant that does not pose a significant health risk.. This health guideline protects against system toxicity.

ppb = parts per billion

All test results

Date Lab ID Result
2012-01-31573078DF4.50 ppb
2012-04-16577594DF2.40 ppb
2012-07-23582213DF10.00 ppb
2013-01-28591890DF5.50 ppb
2013-04-22594912DF6.40 ppb
2013-07-22599348DF6.00 ppb
2013-10-22604844DF2.60 ppb
2014-01-05281733.90 ppb
2014-04-21993232.50 ppb
2014-07-211544202.10 ppb
2014-10-202169453.60 ppb
2015-01-202642262.60 ppb
2015-04-203158382.70 ppb
2015-07-203691583.30 ppb
2015-10-194208762.70 ppb
2016-01-044686552.80 ppb
2016-04-055201152.10 ppb
2016-07-185846834.50 ppb
2016-10-116413413.50 ppb
2017-01-096794922.00 ppb
2017-04-187435194.00 ppb
2017-07-248031132.20 ppb
2017-10-028512162.10 ppb