Add To Favorites
Explainer-What is fluoride and why is it added to the US water supply?
- 5/15/2025
(Reuters) -Florida on Thursday became the second U.S. state to prohibit fluoride, a mineral used for decades to protect teeth from decay, in its water systems.
The move is part of a broader push by U.S. Department of Health and Human Services Secretary Robert F. Kennedy Jr. and conservatives across the country to ban the use of the mineral, which strengthens tooth enamel and promotes dental health.
In March, Utah became the first U.S. state to ban fluoride in water supplies. The Food and Drug Administration said this week it was starting a process to remove fluoride supplements for children from the market.
Here is what you need to know about fluoridation of drinking water as a public health measure:
WHAT IS FLUORIDE AND WHAT ARE ITS BENEFITS?
Fluoride, a mineral that occurs naturally in water, soil and air, has been shown to prevent dental cavities, or tooth decay. It works by strengthening the tooth's enamel, its hard outer surface, making it more resistant to the acid produced by bacteria that cause tooth decay. Fluoride also reverses early tooth decay by replacing and preventing loss of minerals in teeth.
Before community water fluoridation, tooth decay was widespread and severe among Americans. After fluoride was added to the water supply in many places in the U.S., tooth decay declined in both children and adults, and complete tooth loss in older adults became more rare, according to federal health officials.
WHEN DID WATER FLUORIDATION AS A POLICY BEGIN?
In the early 20th century, some U.S. researchers observed that people in areas where the community water supplies were naturally high in fluoride had teeth that were resistant to decay.
In 1945, Grand Rapids, Michigan became the first U.S. city to add fluoride to its water supply in a controlled manner, kicking off what was in effect a large-scale public health experiment. Data over a 15-year span showed a reduction of more than 60% in tooth decay among 30,000 school children in Grand Rapids, demonstrating fluoride's protective benefits.
By the 1950s, the U.S. government's Public Health Service and the American Dental Association acknowledged the success of water fluoridation in reducing cavities. That led to the broad U.S. adoption of adding fluoride in community water supplies and eventually its inclusion in dental products such as toothpaste and mouthwash.
No federal law mandates fluoridation of water supplies. The decision to fluoridate water is typically made by municipal governments, city councils or local water authorities.
HOW WIDESPREAD IS FLUORIDATION IN THE U.S.?
About 63% of all Americans have fluoride in their community water systems as of 2022, according to the U.S. Centers for Disease Control and Prevention.
The average cost per year for U.S. communities to fluoridate their water supplies ranges from 50 cents per person for large communities to $3 per person for small communities, according to the American Dental Association.
In most of the world, fluoride is not added to the public water supply. Some countries add fluoride to table salt. In some regions, fluoride levels in water are naturally high.
ARE FLUORIDE LEVELS REGULATED?
The U.S. Public Health Service recommends that drinking water levels for fluoride remain below 0.7 milligrams per liter. Levels above 1.5 mg/l are known to increase health risks such as bone fractures, thyroid disease and nervous system damage.
The enforceable limit as set by the U.S. Environmental Protection Agency is 4.0 mg/l. A federal judge in California recently ordered the EPA to strengthen its regulations.
WHAT COMPANIES MAKE FLUORIDE?
Fluorosilicic acid is the compound most widely used in water systems as it yields free fluoride rapidly when mixed with water. J.R. Simplot and Nutrien's PCS Phosphate Co are among companies that manufacture the product, according to the EPA.
Total U.S. domestic production of fluorosilicic acid from phosphate rock was about 29 million kilograms (32,000 tons) in 2019, according to EPA statistics.
WHAT HAS KENNEDY SAID ABOUT FLUORIDE?
The U.S. health secretary has claimed, without conclusive evidence, that water fluoridation at U.S. levels is associated with numerous health issues including cancer.
WHAT DO PUBLIC HEALTH EXPERTS SAY?
The CDC has called fluoridation of drinking water one of the nation's top 10 public health achievements of the 20th century, noting that it effectively prevents tooth decay regardless of a person's socioeconomic status or access to care.
The American Dental Association has reiterated its support for community water fluoridation to help prevent tooth decay. Studies show that community water fluoridation reduces tooth decay by more than 25% in children and adults even in an era with widespread availability of fluoride from other sources such as toothpaste, the association said.
WHAT QUESTIONS DO RECENT STUDIES RAISE ABOUT FLUORIDE?
A review published in October 2024 by the Cochrane Database of Systematic Reviews raised questions about the value of fluoridation of public drinking water in wealthy countries based on the findings of 157 studies.
The research suggests that given the widespread addition of fluoride to toothpaste since 1975, community water fluoridation may now have only modest benefits in reducing tooth decay and increasing cavity-free children, compared with the effects seen in earlier studies. New lawsuits, however, are challenging manufacturers on the safety of fluoride levels in toothpaste, too.
The review also found there is not enough evidence to determine the impact of stopping fluoridation or its effect on socioeconomic disparities in dental health.
In January, researchers at the U.S. National Institutes of Health who analyzed 74 studies from 10 countries found IQs were lower in children with higher fluoride exposure. In four studies with a low risk of bias involving?4,179 children, urinary fluoride concentrations at levels reportedly common in developed countries were associated with lower IQ scores, the researchers reported.
The results "support concerns for vulnerable populations living in communities with fluoridated water," according to an editorial published with the report. A second editorial, however, details multiple weaknesses of the NIH analyses and warns that public policy concerning fluoride "should not be affected by the study findings."
(Compiled by Reuters staff; Editing by Nancy Lapid and Bill Berkrot)