Fluoride occurs naturally in most U.S. water sources but at levels too low to strengthen teeth. Since 1945, many U.S. communities have added a small amount of fluoride to water (enough to reach 0.7 mg/L) to help prevent cavities. Current research has not found adverse health effects at these levels. If concentrations reach 2.0 mg/L -- three times higher than in communities with fluoridated water – it can cause dental fluorosis in children or white spotting on teeth. Researchers are still learning about other health effects from exposure at these elevated levels.

High concentrations of fluoride can happen in areas where high levels of fluorine naturally occur In the U.S., this affects less than 1% of the population. Research studies on the dangers of fluoride in drinking water are mostly from countries with these high concentrations of fluorine in their soil, and levels of fluoride in water above 2.0 mg/L. These countries do not add fluoride to water, it is there because of high levels in the soil and bedrock.

Fluoridated water has reduced the number of cavities among children, adolescents, and adults, The greatest decrease in cavities was found in the 1900s, before fluoride was added to toothpaste. Still, the effectiveness of fluoride toothpaste in preventing cavities depends on how often toothpaste is used.

The CDC recommends a fluoride level of 0.7 mg/L as an optimal level to help prevent cavities. There is no federal regulation stating that communities must add fluoride to water, this choice happens at a state or municipality level.

If you get water from a town water supply, you can check if your water is fluoridated on the CDC website or your county’s water information page.

If your water is not fluoridated, parents of children can talk to their child’s dentist or pediatrician to see if fluoride supplements are needed.

If fluoride levels in water rise above 2.0 mg/L municipalities are required to alert their community members. This is because these levels increase the risk of dental fluorosis in children, which is a mild condition that causes white spots or pitting on teeth. This can also happen if a child consistently swallows toothpaste.

If you have well water and are concerned about the level of fluoride, you can test your water to determine the concentration. If the levels are above 2mg/L, you can get a filter to help remove fluoride, and if it is above 4 mg/L you should contact your local health department for next steps.

Some studies have linked high fluoride concentrations to lower IQ in children, more information on these studies is available through the National Toxicology Program.

More research is needed on the long-term health effects of higher concentrations of fluoride in water.