EWG's Tap Water Database — 2021 UPDATE



City of Chicago

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
20140.959 ppm220.941 ppm - 0.977 ppm
20150.825 ppm220.803 ppm - 0.846 ppm
20160.655 ppm220.652 ppm - 0.657 ppm
20170.559 ppm220.539 ppm - 0.579 ppm
20180.609 ppm220.601 ppm - 0.617 ppm
20190.675 ppm220.670 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
2014-02-11SB40289-01_020.941 ppm
2014-02-11SB40288-01_020.977 ppm
2015-01-12SA50259-01_020.846 ppm
2015-01-12SA50260-01_020.803 ppm
2016-01-2616A0568-01_020.652 ppm
2016-01-2616A0570-01_020.657 ppm
2017-01-3017A0785-01_020.579 ppm
2017-01-3017B0033-01_020.539 ppm
2018-01-2318A0437-01_020.601 ppm
2018-01-2318A0437-02_020.617 ppm
2019-02-0519B0088-010.680 ppm
2019-02-0519B0093-010.670 ppm