Fluoride Addition

Fluoride compounds are salts that form when the element, fluorine, combines with minerals in soil or rocks. Fluoridation is the adjustment or addition of fluoride to drinking water at a level that is recommended for reduction of tooth decay.

Stacey Herreid

Rule Manager

P: 701-328-5287
E: sherreid@nd.gov

Fact Sheet


  • What is the maximum contaminant level (MCL) and maximum contaminant level goal (MCLG) for fluoride?
    • The MCL and MCLG for fluoride is 4 mg/L or 4ppm. EPA has also set a secondary standard (SMCL) for fluoride at 2.0 mg/L or 2.0 ppm. 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. The secondary standard of 2.0 mg/L is intended as a guideline for an upper bound level in areas which have high levels of naturally occurring fluoride. The level of the SMCL was set based upon a balancing of the beneficial effects of protection from tooth decay and the undesirable effects of excessive exposures leading to discoloration.
  • Why is fluoride added to drinking water?
    • All water naturally contains some fluoride and fluoride at the right level has been proven to protect teeth from decay. Often, the fluoride level in source water is not enough to provide prevention of tooth decay, therefore, many water systems add fluoride to achieve optimal prevention.
  • What is the fluoride concentration needed to prevent tooth decay?
    • The U.S. Public Health Service (PHS) recommends an optimal fluoride concentration of 0.7 milligrams/liter (mg/L). The optimal concentration of fluoride in drinking water is the concentration that provides the best balance of protection from dental caries while limiting the risk of dental fluorosis.
      Dental fluorosis is a change in the appearance of the tooth's enamel. These changes can vary from barely noticeable white spots in mild forms to staining and pitting in the more severe forms. Dental fluorosis only occurs when younger children (age 8 and under) consume too much fluoride, from any source, over long periods when teeth are developing under the gums.
  • Why did the recommended optimal fluoride concentration change?
    • In 1962 the PHS provided recommendations regarding the optimal fluoride concentrations in drinking water based upon outdoor air temperature of geographic areas. This recommendation was a range from 0.7 – 1.2 mg/L dependent upon the geographic location of the drinking water. The change from this range to 0.7 mg/L regardless of geographic location was made based upon considerations that included:
      • Scientific evidence related to the effectiveness of water fluoridation in caries prevention and control across all age groups,
      • Fluoride in drinking water as one of several available fluoride sources,
      • Trends in the prevalence and severity of dental fluorosis, and
      • Current evidence on fluid intake of children across various outdoor air temperatures.
  • What are water systems’ responsibilities for fluoride addition?
    • Fluoride levels must be monitored daily and a log of these measurements must be kept onsite. A minimum of one monthly sample must be collected and submitted to a certified lab for analysis. This result and the result obtained by the operator onsite at the time of collection must be reported to the DWP monthly.