EWG's Tap Water Database — 2019 UPDATE



City of Chino Hills

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
20120.400 ppm110.400 ppm
20130.800 ppm110.800 ppm
20140.250 ppm220.200 ppm - 0.300 ppm
20160.250 ppm220.1000 ppm - 0.400 ppm
20170.203 ppm440.160 ppm - 0.270 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
2012-07-184790-014-11300.400 ppm
2013-09-184790-014-12300.800 ppm
2014-01-234790-001-13000.200 ppm
2014-01-234790-017-13300.300 ppm
2016-03-034790-014-11300.400 ppm
2016-03-034790-024-10300.1000 ppm
2017-02-169588-001-10100.210 ppm
2017-02-169588-017-10400.270 ppm
2017-04-199588-009-10300.170 ppm
2017-04-199588-010-09450.160 ppm