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Fate and Transport
CAS Number: 7664-39-3
Synonyms: fluorhydric acid, fluoric acid, hydrofluoric acid, hydrofluoride
Contaminant Type: Chemical

Fluoride is a naturally occurring element found in the earth’s crust.  Fluoride compounds are also utilized in industry applications for the production of semiconductors, fertilizers, high purity graphite, and nuclear applications [1892]. 

Low levels of fluoride occur naturally in most sources of drinking water.  Fluoride can occur naturally in surface waters from the deposition of particles in the atmosphere and weathering of fluoride containing rocks and soils. Fluoride in groundwater occurs from leaching from rock formations.  Fluoride is also introduced in water by various human activities such as chemical manufacturing plants and production of fluoridated chemicals [1956][1960]. 

In drinking water treatment, fluoride may be applied at low levels to aid in dental and skeletal health.  The target range of fluoride in drinking water is 0.7 to 1.2 mg/L [1957][1961].

The US EPA has established a maximum contaminant level (MCL) of 4 ppm as long-term exposure to elevated levels of fluoride may lead to bone disease or dental diseae, and a secondary MCL of 2 ppm based on tooth discoloration and pitting. 

In January 2011 the USEPA stated its intent to review the MCL to determine whether revisions are appropriate. 

The US EPA has identified the following treatment processes as Best Available Technologies (BATs) for control of fluoride in drinking water: reverse osmosis and activated alumina [1957].  Because of the high effectiveness of the BATs, treatment would not be a limiting factor if a lower MCL was set [2009].   

Other treatment technologies available for fluoride removal include: ion exchange, lime softening, electrodialysis, and adsorption with various types of media including activated carbon, bone chars and clays [1895][1957][1958]. 

In some regions of the world, fluoride concentrations up to 35 mg/L have been detected in groundwater; the fluoride concentration in surface waters is typically less than 0.3 mg/L [1857]. In general, groundwater with high fluoride content is soft, has high pH and has a high concentration of silica; however, the fluoride concentration can vary depending on the geological, chemical, and physical characteristics of the aquifer, the porosity and acidity of the soils and rock, temperature, and well depth [1857]. 

Date of Literature Search: July 2010

1857 Meenakshi and Maheshwari, R.; 2006; Fluoride in drinking water and its removal; J. Hazardous Materials; B137:456-463
1875 Hichour, M., Persin, F., Molenat, J., Sandeaux, J., and Gavach, C.; 1999; Fluoride removal from diluted solutions by Donnan dialysis with anion-exchange membranes; Desalination; 122:53-62
1892 Cengeloglu, Y., Kir, E. and Ersoz, M.; 2002; Removal of fluoride from aqueous solution by using red mud; Separation and Purification Technology; 28:81
1895 Sorg, T.; 1978; Treatment Technology to Meet the Interim Primary Drinking Water Regulations for Inorganics; JAWWA; 70:2:105
1956 Fawell, J., Ohaniam, E., Giddings, M., Toft, P., Magara, Y. and Jackson, P.; 2004; Fluoride in Drinking Water - Background document for development of WHO Guidelines in Drinking-Water Quality; Fluoride in Drinking Water - Background document for development of WHO Guidelines in Drinking-Water Quality; Report No. WHO/SDE/WSH/03.04/96
1957 USEPA; 2010; Basic Information About Fluoride in Drinking Water; http://water.epa.gov/drink/contaminants/basicinformation/fluoride.cfm; As posted on October 7, 2010. EPA Office of Water, Washignton, D.C.
1958 U.S. Department of the Interior Bureau of Reclamation; 2001; Fluoride Fact Sheet; Fluoride Fact Sheet; Bureau of Reclamation, Technical Service Center, Water Treatment Engineering and Research Group. Denver, CO
1960 Health Canada; 2009; Fluoride in Drinking Water; Guidelines for Canadian Drinking Water Quality: Guideline Technical Document;
1961 Lauer, B. and Rubel, F.; 2004; Water Fluoridation Principles and Practices; Water Fluoridation Principles and Practices; Manual of Water Supply Practices - M4. 5th Edition. American Water Works Association. Denver, CO.
2009 USEPA ; 2003; Water Treatment Technology Feasibility Support Document for Chemical Contaminants; In Support of EPA Six-Year Review of National Primary Drinking Water Regulations; Office of Ground Water and Drinking Water, Standards and Risk Management Division, Washington, DC; EPA 815-R-03-004