EWG's Tap Water Database — 2019 UPDATE



Arapahoe Cnty Wwwa

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
20120.820 ppm770.300 ppm - 1.50 ppm
20140.960 ppm220.820 ppm - 1.10 ppm
20150.784 ppm550.250 ppm - 1.30 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 Result
2012-01-131.30 ppm
2012-01-130.300 ppm
2012-01-230.670 ppm
2012-01-231.50 ppm
2012-04-060.530 ppm
2012-04-061.000 ppm
2012-04-090.440 ppm
2014-12-080.820 ppm
2014-12-081.10 ppm
2015-08-050.890 ppm
2015-08-050.250 ppm
2015-08-050.490 ppm
2015-08-051.30 ppm
2015-11-300.990 ppm