EXPLAINER

US Health and Human Services Secretary Robert F. Kennedy Jr. and conservatives across the country have been working to ban the use of fluoride, which strengthens tooth enamel and promotes dental health. Recently, Colgate-Palmolive agreed to transform its marketing and packaging of toothpaste for small children to show pea-sized dabs on toothbrushes rather than large swirls over concerns that these amounts would deliver unhealthy doses of fluoride. Florida and Utah have prohibited fluoride, a mineral used for decades to protect teeth from decay, in their water systems.

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. A recent study from Austria, where fluoride levels in water are naturally low, found that children over age 6 should use a full brush length of fluoridated toothpaste twice daily, along with an additional fluoride source such as fluoridated salt, mouthwashes or gels. The average cost per year for US 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.

 Here is what you need to know about fluoridation of drinking water as a public health measure:

WHAT IS FLUORIDE

Fluoride, a mineral that occurs naturally in water, soil and air, has been shown to prevent dental cavities, or tooth decay.

BENEFITS

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 US, 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 US?

In the early 20th century, some US 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 US 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 US government's Public Health Service and the American Dental Association acknowledged the success of water fluoridation in reducing cavities. That led to the broad US adoption of adding fluoride to 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 US?

About 63% of all Americans had fluoride in their community water systems as of 2022, the latest year for which data is available, according to the US Centers for Disease Control and Prevention. Earlier this year, Utah and Florida passed laws to ban fluoride in water supplies, and the Food and Drug Administration said it was starting a process to remove fluoride supplements for children from the market. Most people in Utah live in areas without enough natural fluoride in the water to protect their teeth and they should therefore seek fluoride supplements, the Utah Department of Health and Human Services warns.

ARE FLUORIDE LEVELS REGULATED?

The US Public Health Service recommends that drinking water levels for fluoride remain below 0.7 mg per litre. 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 US Environmental Protection Agency is 4.0 mg/l. 

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 US National Institutes of Health who analysed 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."