EWG's Tap Water Database — 2019 UPDATE



City of Garden Grove

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
20120.418 ppm440.370 ppm - 0.460 ppm
20140.443 ppm880.410 ppm - 0.500 ppm
20150.460 ppm440.450 ppm - 0.470 ppm
20170.449 ppm10100.420 ppm - 0.490 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
2012-01-114417-061-09400.390 ppm
2012-01-114417-020-09000.370 ppm
2012-04-044417-018-11050.450 ppm
2012-04-044417-016-11350.460 ppm
2014-01-084417-009-08350.420 ppm
2014-01-084417-011-11000.500 ppm
2014-01-084417-012-09550.410 ppm
2014-01-084417-014-07400.420 ppm
2014-01-084417-019-08100.420 ppm
2014-04-024417-013-14400.490 ppm
2014-04-024417-039-10150.410 ppm
2014-04-024417-006-14000.470 ppm
2015-03-044417-061-08350.450 ppm
2015-03-044417-020-07000.460 ppm
2015-04-014417-016-11400.470 ppm
2015-04-014417-018-11000.460 ppm
2017-02-014417-012-09150.430 ppm
2017-02-014417-014-09350.440 ppm
2017-02-014417-009-08200.460 ppm
2017-02-014417-019-07150.440 ppm
2017-03-014417-018-10500.420 ppm
2017-03-014417-011-10200.480 ppm
2017-04-264417-016-11200.450 ppm
2017-04-264417-013-12000.450 ppm
2017-04-264417-011-10200.490 ppm
2017-04-264417-039-09550.430 ppm