EWG's Tap Water Database — 2021 UPDATE



Jefferson Water Department

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
20170.629 ppm330.576 ppm - 0.691 ppm
20180.660 ppm12120.496 ppm - 0.901 ppm
20190.634 ppm12120.509 ppm - 0.930 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
2017-10-17BC937090.691 ppm
2017-11-15BE339890.621 ppm
2017-12-13BF396340.576 ppm
2018-01-10BF617540.648 ppm
2018-02-13BF776900.775 ppm
2018-03-14BF913780.786 ppm
2018-04-16BG241020.575 ppm
2018-05-09BG553740.496 ppm
2018-06-13BH114530.583 ppm
2018-07-11BH432670.901 ppm
2018-08-08BH771390.617 ppm
2018-09-12BI094280.575 ppm
2018-10-10BI484610.656 ppm
2018-11-14BJ891490.692 ppm
2018-12-11BK773500.620 ppm
2019-01-09BL042690.663 ppm
2019-02-13BL253450.762 ppm
2019-03-13BL377960.749 ppm
2019-04-09OE7943450.930 ppm
2019-05-09BM316280.598 ppm
2019-06-12BM679240.513 ppm
2019-07-10BP059680.566 ppm
2019-08-14BP443460.547 ppm
2019-09-11BP698490.648 ppm
2019-10-10BQ006650.509 ppm
2019-11-13BR369600.600 ppm
2019-12-11BS383430.526 ppm