EWG's Tap Water Database



Marvell Waterworks

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
20100.738 ppm12120.580 ppm - 0.920 ppm
20110.793 ppm13130.470 ppm - 1.01 ppm
20120.566 ppm13130.260 ppm - 0.780 ppm
20130.673 ppm12120.450 ppm - 0.890 ppm
20140.672 ppm11110.450 ppm - 0.800 ppm
20150.657 ppm330.620 ppm - 0.710 ppm

ppm = parts per million.

State and national drinking water standards and health guidelines

EPA Maximum Contaminant
Level (MCL) 4 ppm

The enforceable federal standard that defines the highest level of a contaminant allowed in drinking water.

ppm = parts per million.

EPA Maximum Contaminant
Level Goal (MCLG)4 ppm

A non-enforceable federal health guideline. For cancer-causing chemicals, these health goals are typically set to zero.

ppm = parts per million.

All test results

Date Lab ID Result
2010-01-051001100230.920 ppm
2010-02-221006000160.830 ppm
2010-03-151008100250.800 ppm
2010-04-121010900130.580 ppm
2010-05-101013700420.610 ppm
2010-06-141017200170.620 ppm
2010-07-121020100370.680 ppm
2010-08-091022800110.780 ppm
2010-09-271027700010.720 ppm
2010-10-181029800140.720 ppm
2010-11-151032600140.720 ppm
2010-12-201036100020.880 ppm
2011-01-121101800050.960 ppm
2011-02-211105900121.01 ppm
2011-03-281109400010.850 ppm
2011-04-111110800380.940 ppm
2011-05-091113600090.980 ppm
2011-06-211118200240.840 ppm
2011-07-111119900250.750 ppm
2011-08-081122700270.770 ppm
2011-09-261127600100.510 ppm
2011-10-031128300090.470 ppm
2011-11-051131800080.770 ppm
2011-12-101135300110.710 ppm
2011-12-261203000180.750 ppm
2012-02-05Y803900390.740 ppm
2012-02-211205300280.590 ppm
2012-03-131207900190.740 ppm
2012-04-231212100130.780 ppm
2012-04-231211700040.780 ppm
2012-05-221215000120.600 ppm
2012-06-191217700050.560 ppm
2012-07-191220500120.370 ppm
2012-08-151223400080.340 ppm
2012-09-131226100200.260 ppm
2012-10-221230300030.570 ppm
2012-11-281233800180.490 ppm
2012-12-161235500130.540 ppm
2013-01-031301400030.610 ppm
2013-02-231306300030.690 ppm
2013-03-021307000150.770 ppm
2013-04-141311300080.700 ppm
2013-05-121314100160.720 ppm
2013-06-161317500120.640 ppm
2013-07-141320300140.640 ppm
2013-08-111323200170.450 ppm
2013-09-281328100050.570 ppm
2013-10-301331000230.710 ppm
2013-11-161332400250.680 ppm
2013-12-281400800010.890 ppm
2014-01-121402200070.720 ppm
2014-02-171405500320.800 ppm
2014-03-291409700130.650 ppm
2014-04-251412500050.620 ppm
2014-05-041413200250.690 ppm
2014-06-011416000170.450 ppm
2014-07-201421100150.720 ppm
2014-08-101423000320.790 ppm
2014-10-21Y1430000310.700 ppm
2014-11-09Y1432100320.750 ppm
2014-12-24Y1501300040.500 ppm
2015-01-04Y1501300450.620 ppm
2015-05-05Y1512700380.640 ppm
2015-08-31Y1526500040.710 ppm