EWG's Tap Water Database — 2019 UPDATE



Town of Gilbert

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
20120.635 ppm2827ND - 1.000 ppm
20130.570 ppm1211ND - 0.810 ppm
20140.620 ppm110.620 ppm
20150.510 ppm110.510 ppm
20160.579 ppm10100.280 ppm - 0.940 ppm
20170.650 ppm110.650 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
2012-01-09PVA0476-010.410 ppm
2012-01-09PVA0475-01I0.440 ppm
2012-01-12PVA0815-010.660 ppm
2012-01-12PVA0814-010.650 ppm
2012-01-17PVA1028-010.580 ppm
2012-01-18PVA1137-010.730 ppm
2012-01-19PVA1240-010.700 ppm
2012-01-25PVA1556-010.500 ppm
2012-02-13PVB0899-010.980 ppm
2012-02-13PVB0898-010.950 ppm
2012-02-13PVB0897-010.790 ppm
2012-02-28PVB1867-01B0.590 ppm
2012-03-01PVC0073-01B0.460 ppm
2012-03-15PVC1257-01I0.500 ppm
2012-03-27PVC1957-010.850 ppm
2012-04-02PVD0064-010.540 ppm
2012-04-09PVD0611-01I0.920 ppm
2012-04-23PVD1652-010.440 ppm
2012-05-02PVE0219-01I0.700 ppm
2012-07-02PVG0068-01B0.530 ppm
2012-07-02PVG0062-01B0.520 ppm
2012-07-26PVG1876-010.670 ppm
2012-08-01PVH0103-011.000 ppm
2012-08-28PVH2122-010.600 ppm
2012-10-01PVJ0070-01I0.680 ppm
2012-10-01PVJ0072-01I0.720 ppm
2012-12-20PVL1426-01I0.660 ppm
2013-07-29550-7634-1I0.720 ppm
2013-07-30550-7716-1I0.560 ppm
2013-07-30550-7713-10.630 ppm
2013-07-31550-7815-1I0.570 ppm
2013-07-31550-7810-1I0.780 ppm
2013-08-07550-8302-10.620 ppm
2013-08-12550-8579-10.740 ppm
2013-08-13550-8672-10.810 ppm
2013-08-26550-9435-1I0.610 ppm
2013-10-15201310150527I0.360 ppm
2013-10-22201310220364I0.440 ppm
2014-01-27201401270086I0.620 ppm
2015-01-28201501280356I0.510 ppm
2016-01-12201601120223I0.560 ppm
2016-01-19201601190321I0.690 ppm
2016-01-26201601260298I0.940 ppm
2016-02-08201602080053I0.280 ppm
2016-02-08201602080042I0.470 ppm
2016-03-02201603020441I0.500 ppm
2016-03-23201603230453I0.560 ppm
2016-04-07201604070686I0.690 ppm
2016-04-19201604190185I0.470 ppm
2016-05-31201605310460I0.630 ppm
2017-01-0420170104081510.650 ppm