Flouride in Drinking Water

Fluorine is a natural trace element and exists in almost all soils. Fluoride is classified as any binary compound of fluorine with another element. Perhaps the most widely known use of fluoride is its addition to public drinking water supplies at about one milligram per liter (mg/L) of a fluoride salt, measured as fluoride, for the purpose of reducing tooth decay. 

Children under nine years of age exposed to levels of fluoride greater than about 2 mg/L may develop a condition known as mottling or discoloration of the permanent teeth. Exposure to drinking water levels above 4 mg/L for many years may result in cases of crippling skeletal fluorosis, which is a serious bone disorder resembling osteopetrosis and characterized by extreme density and hardness and abnormal fragility of the bones (sometimes called “marble bones”). 

Contaminant  In Water As Maximum Contaminant Level

Fluoride (F)

Fluoride, F-

MCL* = 4.0 mg/L or ppm
Secondary Standard** = 2.0 mg/L or ppm
WHO Guideline = 1.5 mg/L

Sources of Contaminant

Natural deposits
Municipally treated drinking water (>2 mg/L, potentially as a result of poorly monitored or malfunctioning feeding equipment)

Potential Health Effects

Skeletal fluorosis, from long-term consumption >4 mg/L (a serious bone disorder resembling osteoporosis and characterized by extreme density and hardness and abnormal fragility of the bones)

Potential Aesthetic Effects

Mottling (discoloration) of teeth in children under 9 years of age (from long-term consumption at >2 mg/L)
Disfiguration/pitting of teeth in children

Treatment Methods

Point-of-Entry (POE)
Point-of-Use (POU)

Reverse osmosis
Strong base anion exchange (Cl- form)
Activated alumina adsorption media

*Maximum Contaminant Level (MCL) - The highest level of a contaminant that is allowed in drinking water. MCLs are set as close to MCLGs as feasible using the best available treatment technology and taking cost into consideration. MCLs are enforceable standards.

**National Secondary Drinking Water Regulations (NSDWRs or secondary standards) are non-enforceable guidelines regulating contaminants that may cause cosmetic effects (such as skin or tooth discoloration) or aesthetic effects (such as taste, odor, or color) in drinking water. EPA recommends secondary standards to water systems but does not require systems to comply. However, states may choose to adopt them as enforceable standards.

WHO† - World Health Organization

Click here to open WQA's Technical Fact Sheet on Fluoride.

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