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Fluoride in water: Is it dangerous?

This week, 16% of St. Louis adults surveyed reported that in the last 7 days they had heard that “all fluoride in water is dangerous;” of those who heard it 46% thought it was probably or definitely true. 

What is fluoride?

Fluoride is a natural mineral found in water, soil, air, and certain foods. In the U.S., most people get fluoride from their toothpaste or local water supply. It strengthens teeth and bones and prevents cavities. It is absorbed in the gut and stored in bones and teeth. Excess fluoride is excreted in urine.   

Why is fluoride added to water?

Bacteria in the mouth produce acid that can lead to tooth decay. Fluoride reduces acid production in saliva and strengthens enamel, the tooth’s protective outer layer. In 1945, Grand Rapids, MI was the first city to fluoridate its water. Over the next decade, childhood cavities in Grand Rapids dropped by 60%. By 2020, 209 million U.S. residents lived in communities with fluoridated water. 

Is fluoride in water safe?

The level of fluoride needed to reduce cavities without increasing fluorosis (mild discoloring of teeth) is 0.7 milligrams per liter of water. This means one part fluoride for every 1.4 million parts of water. Communities that add fluoride to their water must carefully monitor this level, because fluoride levels above 1.5 milligrams per liter – over twice the recommended level –  have been linked to lower IQ in children, according to the U.S. National Toxicology Program.   

What’s the debate? 

Some question whether adding fluoride to local water systems is still necessary. They argue that people get enough fluoride from toothpaste and mouthwash, and to a much lesser degree from drinks like coffee and black tea, and foods like oatmeal, raisins and potatoes. On the other hand, fluoridated water may be the only source of fluoride for some, especially those with limited means.  

Help St. Louis residents stay informed   

Over 100 communities in Missouri fluoridate their water. Is yours one of them?  You can check here.  Please share the resources below to help educate St. Louisans about water fluoridation. 

Survey information

This week’s report is based on a survey of 249 adult residents in St. Louis, MO (n = 163) and Omaha, NE (n = 86), conducted from November 16-18, 2024. Explore these data and more at iHeardSTL.


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Community water fluoridation is a strategy for preventing cavities in the U.S. 

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