EWG's Tap Water Database — 2019 UPDATE



City of Baltimore

Fluoride occurs naturally in surface and groundwater and is also added to drinking water by many water systems. Read More.

Fluoride has been promoted as a chemical that reduces dental cavities. Yet it is now well-established that fluoride primarily exerts its protective effects through topical mechanisms, such as sodium fluoride in toothpaste and mouthwash. In contrast, long-term ingestion of fluoride in water increases dental fluorosis, which includes mottling, pitting and weakening of the teeth. EPA's maximum legal limit is set at 4 parts per million (ppm) to prevent skeletal fluorosis, a condition where bones become brittle and more susceptible to fractures, although these effects may occur at lower doses.

Even fluoride levels of 0.7 ppm, the amount of fluoride in drinking water recommended by the U.S. Public Health Service, can result in too much fluoride for bottle-fed babies. EWG recommends that caregivers mix baby formula with fluoride-free water. The National Toxicology Program is investigating the potential for low doses of fluoride to alter thyroid function and childhood brain development.





Samples exceeding legal limit (MCL)


Samples exceeding
health guidelines

Testing results - average by year

YearAverage resultSamples takenDetectionsRange of results
20120.804 ppm330.700 ppm - 1.000 ppm
20130.897 ppm330.770 ppm - 1.06 ppm
20140.611 ppm770.600 ppm - 0.640 ppm
20150.985 ppm440.680 ppm - 1.62 ppm
20160.740 ppm550.710 ppm - 0.790 ppm
20170.725 ppm550.643 ppm - 0.770 ppm

ppm = parts per million

State and national drinking water standards and health guidelines

EPA Maximum Contaminant
Level (MCL) 4 ppm

ppm = parts per million

All test results

Date Lab ID Result
2012-02-07120207_01_TREATE0.711 ppm
2012-05-08120508_02_T111.000 ppm
2012-05-22120522_02_T410.700 ppm
2013-01-23130123_01_COB0120.770 ppm
2013-05-29130529_02_COB0521.06 ppm
2013-05-29130529_02_CB05290.860 ppm
2014-01-06140106_01_COB0100.600 ppm
2014-01-06BC010620140.600 ppm
2014-04-08140408_01_COB0400.600 ppm
2014-04-08140408_02_COB0400.600 ppm
2014-04-08MONTEBELLO_PLANT0.600 ppm
2014-06-23140623_01_COB0620.640 ppm
2014-06-23MONTEBELLO_PLANT0.640 ppm
2015-01-05TREATED_GRAB_T0.750 ppm
2015-04-02MONTEBELLO_PLANT0.680 ppm
2015-04-15MONTEBELLO_PLANT0.890 ppm
2015-04-15MONTEBELLO_PLANT1.62 ppm
2016-01-01TP01_160101_010.740 ppm
2016-05-25TP02_160525_020.790 ppm
2016-05-25TP02_160525_010.740 ppm
2016-06-01TP02_160601_020.710 ppm
2016-06-01TP02_160601_010.720 ppm
2017-05-01TP01_170501_010.643 ppm
2017-05-03TP01_170503_010.770 ppm
2017-05-030300002_051317_T0.733 ppm
2017-05-05TP02_170505_010.753 ppm
2017-05-07TP02_170507_010.725 ppm