Utah became the first US state to ban fluoride from being added to public drinking water in March. Soon after Florida followed suit, with US Health Secretary Robert F Kennedy Jr telling the Centers for Disease Control and Prevention (CDC) to stop recommending fluoridation nationwide.
As opposition to water fluoridation in the US rises, scientists are concerned that its removal will lead to a sharp increase in tooth decay, costing the states billions of dollars and disproportionately affecting poorer communities.
With states such as Nebraska, Kentucky and Louisiana looking to remove fluoride from water, the question of how quickly this change will affect Americans has been raised.
Fluoride fluctuations
Fluoride is a naturally occurring mineral found in fresh water and was first added to community drinking water, in controlled amounts, in the US in 1945 as an effective way to help prevent tooth decay.
Helping to strengthen developing baby teeth and protect them into adulthood, the CDC stated in 1999 that community water fluoridation was one of the 20th century's greatest public health achievements.
In recent years though, the addition of fluoride to sources such as foods, milk and dental products, such as toothpaste and mouthwash, has led to concerns that the combined total intake of fluoride per person may exceed safe amounts.
The National Toxicology Program (NTP) in the US released a review of published scientific studies on the links between fluoride and neurodevelopment and cognition. The findings showed that higher levels of fluoride exposure, such as drinking water containing more than 1.5 milligrams of fluoride per litre, were associated with lower IQ in children.
The NTP conceded, however, that there was insufficient data to determine if the low, US-recommended fluoride levels of 0.7 mg/L has a negative effect on children’s IQ. And, of the 74 non-US-based studies consulted, it said, “52 were rated as low quality (high risk of bias)”.
Vida Zohoori, professor in public health and nutrition at the UK's Teesside University and known for her research on fluorides, says these studies offer insufficient data from which to draw conclusions.
“Most were conducted in regions where fluoride concentrations are well above US standards, limiting their relevance to community water fluoridation at 0.7mg/L,” she says.
“The majority of studies were cross-sectional, rather than longitudinal or randomised, making it impossible to establish causality. Many also failed to control for key variables, such as exposure to iodine or lead, poor nutrition and socioeconomic status – all of which can independently influence child cognitive development.”
But the evidence in favour of adding safe amounts of fluoride to drinking water is robust. Based on a systematic Cochrane review from 2015 (and later updated in 2024), Zohoori projects that if fluoride were removed from public water supplies, we would see large increases in childhood tooth decay, also known as Early Childhood Caries (ECC). This affects children aged one to five, as well as the permanent teeth of 6–12-year-olds, which are highly vulnerable to decay.
It’s a sentiment shared by Dr James Bekker, associate professor at the University of Utah School of Dentistry and specialist in pediatric dentistry. “There are no scientifically viable studies that show detrimental effects of fluoride if added in safe dosages,” he says.
Bekker explains that fluoride in toothpaste provides a topical effect during brushing, whereas small traces in drinking water and supplements offer continuous and systemic exposure, strengthening tooth enamel and making it more resistant to acids.
According to the CDC, water fluoridation reduces tooth decay by about 25 per cent in children and adults. School children living in communities where water is fluoridated have, on average, 2.25 fewer decayed teeth.
“Many children don’t have access to fluoride supplements,” Bekker says, adding that before the ban, water fluoridation was only present in half of Utah.
"In the non-fluoridated water populations, we’ve already seen a significant increase in dental decay, compared to those who have access to fluoridated water. If untreated, cavities get larger and eventually get to the nerve of the tooth, which can lead to infection and potential tooth removal.”
If all 50 US states stopped community water fluoridation programmes, children and adolescents aged 0–19 could expect to develop 25.4 million more cavities within the next five years. This would be the equivalent of a new cavity for one in every three American children, costing a total of $9.8bn (£7.2bn), according to a new study published in JAMA Health Forum in May.
“We specifically measured the increase in dental cavities – the kind that might need anything from a filling to a root canal or even a tooth extraction,” says Dr Lisa Simon, fellow in oral health and medicine integration at Harvard School of Dental Medicine and co-author of the study.
“We included decay in both baby teeth and adult teeth, which start growing in when children are around six years old.”
Lessons learned
With the Utah ban now in place, Bekker estimates it could take five years before we see the full effects. In the city of Calgary, Canada, though, the effects were seen even sooner. In 2011, Calgary removed fluoride from its drinking water and just three years later, the dental decay of children spiked.
In a single year, 32 out of every 10,000 children in Calgary were put under general anaesthesia to treat tooth decay, compared with 17 out of 10,000 in Edmonton, a city in the same province. Calgary has since voted to reinstate fluoride.
Although 63 per cent of the US population receives fluoridated water, most countries don’t add fluoride to their drinking water. Reasons range from its natural occurrence in drinking water to concerns over safety and the belief that people should be able to choose what they ingest.
In the UK, only 10 per cent of people receive purposely fluoridated water, with fluoride occurring naturally in low levels in most drinking water in England and Wales.
But the UK government confirmed in March that it would expand water fluoridation in the north east, after data revealed that one in five children aged five has experienced tooth decay in England, with higher rates of up to one in three in more deprived areas.
The most common reason children aged five to nine are admitted to hospital is to have treatment for decayed teeth.
“Recent studies have shown that the benefit of water fluoridation isn’t as dramatic as it used to be, since fluoride was added to toothpaste and became more widely used from the 1970s,” says Dr Andrew Bain, a general dental practitioner based in London.
“But tooth decay is on the rise and we need better education around dental care. The frequency of sugar intake is key to prevention. So, I would be in support of water fluoridation here in the UK.”
Dr Scott Tomar, professor and associate dean of prevention and public health sciences at the University of Illinois, Chicago, and a spokesman for the American Dental Association, applauds the UK’s water fluoridation extension.
He's concerned that misinformation in the US on fluoride could lead to public fear of the mineral in other forms – including toothpaste – and lead to more bans across US states and communities.
Tomar points out that the support for fluoride across the dentistry community is proof of its success and safety because it goes against the financial interest of dentists – you can make much more money treating problems than preventing them.
“So why would we be championing water fluoridation like this?” he asks. “I’m very concerned because we don’t have great alternatives to fluoride and we can no longer turn to the federal government for support.”
Dentists and industry bodies are, instead, coming together to fight their cause, with the Utah Oral Health Coalition due to launch the Your Smile Matters campaign to promote good oral health.
“We believe this is mostly a political decision," says Lorna Koci, chair of the coalition and program director of Davis Donated Dental, which supports vulnerable communities with dental care. “We continue to believe that water fluoridation is safe – it’s the most effective way to fight decay and the most cost-effective method.”
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