EWG's Tap Water Database — 2019 UPDATE



Golden State Water Company (GSWC) - South Arcadia

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
20120.664 ppm880.430 ppm - 0.880 ppm
20130.673 ppm330.440 ppm - 0.800 ppm
20140.623 ppm330.460 ppm - 0.730 ppm
20150.593 ppm880.420 ppm - 0.800 ppm
20160.620 ppm330.350 ppm - 0.770 ppm
20170.687 ppm330.490 ppm - 0.850 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
2012-08-169588-015-09350.880 ppm
2012-08-169588-014-08500.570 ppm
2012-08-212706-002-12150.830 ppm
2012-08-212706-015-13200.550 ppm
2012-08-212706-014-14200.830 ppm
2012-08-212706-006-13450.510 ppm
2012-08-212706-005-14000.430 ppm
2012-08-212706-003-12200.710 ppm
2013-05-159588-002-10450.800 ppm
2013-05-159588-005-09500.440 ppm
2013-05-232706-004-10400.780 ppm
2014-08-289588-006-11000.460 ppm
2014-08-289588-003-10200.680 ppm
2014-08-289588-004-10300.730 ppm
2015-08-149588-014-11150.450 ppm
2015-08-149588-015-10350.750 ppm
2015-08-172706-006-09150.480 ppm
2015-08-172706-014-09550.440 ppm
2015-08-172706-015-08350.800 ppm
2015-08-172706-002-10430.730 ppm
2015-08-172706-005-09240.420 ppm
2015-08-172706-003-10480.670 ppm
2016-05-119588-005-11050.350 ppm
2016-06-202706-004-10380.770 ppm
2016-06-229588-002-09100.740 ppm
2017-08-109588-003-10000.720 ppm
2017-08-109588-004-10100.850 ppm
2017-08-109588-006-10350.490 ppm