Protecting Public Health and the Environment.

Fluoride in Drinking Water

Fluoride is a naturally occurring compound derived from fluorine, the earth's 13th most abundant element. It is found in many rocks and minerals in the soil and enters drinking water as water passes through these soils. Fluoride is present naturally in almost all foods and beverages including water, but levels can vary widely. Very few public water systems in Idaho add fluoride to the drinking water in a process known as fluoridation.

Fluoride Regulation

Fluoride has been shown to prevent tooth decay, but too much fluoride at an early age while the teeth are forming can cause discoloration and pitting of the teeth.  This condition is known as dental fluorosis. Overexposure to fluoride over a lifetime can lead to certain types of bone disease.

How Much Fluoride is Too Much?

EPA has set a maximum contaminant level (MCL) for fluoride of 4.0 mg/L for drinking water for community public water systems. (There is no drinking water standard for fluoride for noncommunity public water systems.) This means that some people who regularly consume water above this level can experience bone disease. EPA has also set a secondary standard of 2.0 mg/L. Children who regularly consume water above this level may experience dental fluorosis, ranging from white flecks in the mildest forms to brown stains and pitting in the most severe forms.

EPA recommends that children under 9 years old not consume water with fluoride concentrations higher than 2.0 mg/L on a regular basis. Your dentist can help you decide how much fluoride your family and you need.

In January 2011, the United States Department of Health and Human Services (HHS) and EPA announced new scientific assessments of fluoride with the intent to review the existing fluoride standard. HHS proposed a recommended standard of 0.7 mg/L for optimal oral health. In response, EPA is initiating a review of fluoride based on new scientific assessments of the health effects of too much fluoride. EPA has not yet decided whether the MCL should be revised, however, and no time frame has been identified.

Bottled Water and Fluoride

Bottled water is regulated by the United States Food and Drug Administration and must meet federal drinking water standards for regulated contaminants. Some bottled water contains natural levels of fluoride from the location that it was collected. Some companies add fluoride to their bottled water, which must be indicated on the label. Consumers who choose to purchase bottled water should carefully read the label or contact the bottler to understand what they are buying (e.g., water source, treatment method, and fluoride level).

Testing for Fluoride

Several methods are available to determine the general fluoride concentrations in your area:

  • If your water comes from a public water system, ask your water provider. If they are unable to locate the results, download them from the sample result tool on DEQ's website at
  • If you have a private well, have your water tested by a qualified laboratory to determine fluoride concentrations. Your local public health district can assist with testing your drinking water. Generally, follow the simple instructions and take a sample of water to a qualified laboratory for testing. Fluoride levels in drinking water can fluctuate naturally, so this sample may not represent a constant concentration.

If you have been advised by a professional that the concentration of fluoride in your drinking water is determined to be too high, it may be necessary to drink only bottled or properly treated water.

Staff Contacts

Drinking Water Program Manager
Jerri Henry
DEQ State Office
Water Quality Division
1410 N. Hilton
Boise, ID 83706
(208) 373-0471

DEQ Resources

Basic Information: Fluoride in Your Drinking Water

Labs Certified by Idaho to Perform Drinking Water Analyses

More Information

Questions and Answers About Fluoride

My Water's Fluoride
Learn the status of fluoridation in your water system.

Review of the Fluoride Drinking Water Regulation

Fluoride in Your Well Water

Fluoride & Fluoridation

Related Pages

Private Wells