EWG's Tap Water Database — 2019 UPDATE



City of Mesa

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 ppm30300.120 ppm - 1.10 ppm
20130.700 ppm110.700 ppm
20140.650 ppm110.650 ppm
20150.318 ppm3022ND - 1.15 ppm
20160.703 ppm220.693 ppm - 0.712 ppm
20170.700 ppm110.700 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
2012-04-09201204090008I0.150 ppm
2012-04-16201204160112I0.220 ppm
2012-05-07201205070059I0.150 ppm
2012-05-08201205080126I0.290 ppm
2012-08-06201208060117I0.720 ppm
2012-08-06201208060116I0.670 ppm
2012-08-06201208060115I1.10 ppm
2012-08-07201208070367I0.360 ppm
2012-08-08201208080565I0.430 ppm
2012-08-08201208080564I0.310 ppm
2012-08-08201208080563I0.470 ppm
2012-08-13201208130185I0.460 ppm
2012-08-13201208130184I0.280 ppm
2012-08-13201208130183I0.170 ppm
2012-08-14201208140228I0.280 ppm
2012-08-14201208140227I0.260 ppm
2012-08-14201208140229I0.170 ppm
2012-08-15201208150503I0.220 ppm
2012-08-15201208150502I0.120 ppm
2012-08-15201208150501I0.270 ppm
2012-08-22120707860.510 ppm
2012-08-22120707830.320 ppm
2012-08-22120707780.390 ppm
2012-08-27120707790.710 ppm
2012-08-27120707720.470 ppm
2012-08-27120707770.910 ppm
2012-08-28120707850.740 ppm
2012-08-28120707810.400 ppm
2012-09-24201209240094I0.330 ppm
2012-11-202012112001155I0.660 ppm
2013-10-14131004950.700 ppm
2014-10-08141002970.650 ppm
2015-04-07150402730.320 ppm
2015-04-07150402720.340 ppm
2015-04-07150402490.672 ppm
2015-04-21150406060.696 ppm
2015-04-29150407720.303 ppm
2015-04-29150407710.211 ppm
2015-07-06150700770.291 ppm
2015-07-06150700730.624 ppm
2015-07-06150700740.798 ppm
2015-07-06150700760.453 ppm
2015-07-0715070120IOC0.301 ppm
2015-07-0715070119I0.332 ppm
2015-07-07150701170.393 ppm
2015-07-13150702501.15 ppm
2015-07-13150702490.261 ppm
2015-07-13150702510.373 ppm
2015-07-14150702550.481 ppm
2015-07-14150702540.424 ppm
2015-07-14150702530.268 ppm
2015-07-20150703910.272 ppm
2015-07-21150704470.208 ppm
2015-07-27150705410.380 ppm
2016-06-0816060165I0.712 ppm
2016-10-04161000390.693 ppm
2017-10-10171004010.700 ppm