EWG's Tap Water Database — 2019 UPDATE



City of Corsicana

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
20120.175 ppm220.140 ppm - 0.210 ppm
20130.625 ppm220.550 ppm - 0.700 ppm
20140.651 ppm220.554 ppm - 0.747 ppm
20150.681 ppm220.504 ppm - 0.857 ppm
20160.765 ppm220.733 ppm - 0.796 ppm
20170.589 ppm220.571 ppm - 0.607 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
2012-01-0412010670020.140 ppm
2012-01-0412010670010.210 ppm
2013-01-1713014640020.550 ppm
2013-01-1713014640010.700 ppm
2014-05-15Q14165510060.554 ppm
2014-05-15Q14165510050.747 ppm
2015-01-28Q15034090060.857 ppm
2015-01-28Q15034090050.504 ppm
2016-02-02Q16044170060.733 ppm
2016-02-02Q16044170050.796 ppm
2017-01-17Q17020000060.571 ppm
2017-07-26Q17307370080.607 ppm