EWG's Tap Water Database — 2021 UPDATE



City of Flagstaff

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
20140.190 ppm110.190 ppm
20150.0751 ppm660.00870 ppm - 0.120 ppm
20160.132 ppm220.0740 ppm - 0.190 ppm
20170.0957 ppm330.0900 ppm - 0.1000 ppm
20180.0760 ppm110.0760 ppm
20190.0750 ppm110.0750 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
2014-09-042014095050485I0.190 ppm
2015-03-10201503050252I0.00870 ppm
2015-04-14201503050251I0.0730 ppm
2015-07-28201507210370I0.0930 ppm
2015-07-30201507310184I0.1000 ppm
2015-08-27201508280194I0.120 ppm
2015-09-10201509120269I0.0560 ppm
2016-07-25201607260412I0.190 ppm
2016-08-17201608180220I0.0740 ppm
2017-07-05201707061058I0.0970 ppm
2017-08-28201708290221I0.0900 ppm
2017-08-28201708290222I0.1000 ppm
2018-08-27201808280602I0.0760 ppm
2019-04-29201904300311I0.0750 ppm