EWG's Tap Water Database — 2021 UPDATE



City of The Dalles

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
20140.657 ppm330.510 ppm - 0.760 ppm
20150.595 ppm440.430 ppm - 0.750 ppm
20160.640 ppm440.470 ppm - 0.800 ppm
20170.593 ppm330.360 ppm - 0.730 ppm
20180.597 ppm330.440 ppm - 0.680 ppm
20190.583 ppm330.390 ppm - 0.680 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
2014-08-13440857157-I0.700 ppm
2014-08-13440857156-I0.760 ppm
2014-08-13440857154-I0.510 ppm
2015-08-18201506240080-I0.480 ppm
2015-08-18201506240081-I0.430 ppm
2015-08-18201506240082-I0.720 ppm
2015-08-18201506240083-I0.750 ppm
2016-08-23201608150036-I0.800 ppm
2016-08-23201608150035-I0.770 ppm
2016-08-23201608150034-I0.470 ppm
2016-08-23201608150033-I0.520 ppm
2017-08-23V7H052401-I0.360 ppm
2017-08-23V7H052402-I0.690 ppm
2017-08-23V7H052403-I0.730 ppm
2018-08-16V8H037503-I0.440 ppm
2018-08-16V8H037502-I0.670 ppm
2018-08-16V8H037501-I0.680 ppm
2019-08-14B9H225804-I0.390 ppm
2019-08-14B9H225805-I0.680 ppm
2019-08-14B9H225806-I0.680 ppm