Fluoride is back in the news, and for good reason. In a new review of data published this month, scientists found evidence that higher levels of fluoride exposure are associated with a decline in IQ in infants and very young children.
Historically, fluoride was added to our water to strengthen our tooth enamel, which helps prevent tooth decay. In turn, improved dental health in childhood is known to reduce absenteeism from school, lead to less expensive dental procedures, and possibly even reduce the risk of cardiovascular disease later in life.
But this new research, conducted by scientists at the NIH’s National Toxicology Program, suggests that fluoride exposure—and therefore water fluoridation—may be more dangerous than previously thought. They found that children who were exposed to higher levels of fluoride during their earliest years of life had noticeably lower IQ scores, between one and two points to be exact, than children who were exposed to lower levels of fluoride.
review, published in JAMA Pediatricsis not the only recent research to cast doubt on fluoride. A study from last May, for example, found link between higher exposure to fluoride in pregnant women and a higher risk of their children being diagnosed with neurobehavioral problems by the age of three. Some scientists too examined recently is water fluoridation needed anymore to get the benefits of fluoride, since people in many parts of the world can get fluoride from their toothpaste products.
However, the scientific debate about the positive and negative properties of fluorine is not one-sided. Some scientists have criticized methodology and interpretations of a recent review, for example. The study itself could not find it convincing evidence linking lowered IQ to low fluoride exposure, including levels recommended for US drinking water (0.7 milligrams per liter). Other reviews have similarly failed find a link between relatively low fluoride exposure and loss of IQ or impaired development (including after the introduction of the fluoridation program).
Some critics of fluoridation have also tried to blame fluoride for other health problems for which there is much less evidence to support a potential link. Robert F. Kennedy Jr., who is expected to head the US Department of Health and Human Services under the Trump administration, claimed that fluoride is linked to bone cancer, for example, despite most studies finding no significant cancer link.
For this Giz Asks, we reached out to experts to share their thoughts on the latest study, the science of fluoride, and the potential implications of this research. The following answers have been slightly edited and condensed for clarity.
Jay Kumar
Retired epidemiologist specialist in dental medicine and co-author of the book a meta-analysis 2023 on the potential effects of fluoride on IQ in children.
Findings that high levels of fluoride in drinking water in rural areas of China, India, Pakistan, and Iran are associated with IQ deficits are not new. The authors cannot attribute the IQ deficits to fluoride in the water because the quality of the study is low. These studies measured fluoride in drinking water and IQ in children at the same time. For example, it could be that parents with higher IQs moved from regions to avoid high fluoride water because of its well-known risk to teeth and bones, and therefore the absence of higher IQ families may drive the association, and not the other way around. . This potential bias is sometimes known as “cart before horse bias.” Also, animal and human studies cannot explain how fluoride can affect the brain.
We published a study titled “The Association of Low Fluoride Exposure and Children’s Intelligence: A Meta-Analysis Relevant to Community Water Fluoridation.” In this paper, we answered the research question: Does fluoride exposure recommended for caries prevention reduce children’s cognitive ability and IQ scores? Fluoride is recommended at 0.7 mg/L for water supplies in American communities.
Our study concluded that exposure to fluoride at approximately twice the concentration used in community water fluoridation (less than 1.5 mg/L) was not associated with lower IQ scores in children. However, we emphasize the need for additional research to determine whether naturally occurring fluoride in drinking water greater than 1.5 mg/L causes IQ deficits.
AND a recent Australian study by Do et al. reaffirmed findings from Canada, New Zealand and Spain that IQ scores were similar in fluoridated and non-fluoridated areas.
Bruce Lanphear
An epidemiologist at Simon Fraser University who has studied how exposure to fluoride in pregnant women can affect the later development of their children.
Fluoride is a reactive chemical that binds strongly to calcium and metals. In 1944, the Journal of the American Dental Association described fluoridation as “spectacularly attractive” for preventing tooth decay, but warned of the risks of adding a “highly toxic substance” to drinking water. Today, more than 70% of Americans drink tap water fluoridated at about 0.7 [parts per million, or ppm]is considered “optimal”. Fluoride is also present in toothpaste (1000–1500 ppm), black teas (1–6 ppm), foods such as sardines and anchovies (2–4 mg/100 g), certain medications (eg, Prozac, Lipitor), and pesticides . treat products like raisins. Over the past 50 years, the consumption of fluoride has increased, which has contributed to the rise of dental fluorosis – discoloration or staining of the teeth due to excessive exposure to fluoride during development.
What did the research reveal?
Taylor’s team reviewed 74 studies from 10 countries linking fluoride exposure to IQ scores. Although many of the early studies were of lower quality, a meta-analysis of high-quality studies found that a 1 ppm increase in urinary fluoride was associated with a 1.2-point decrease in IQ in children, even at levels below 1.5 ppm. Although these IQ reductions are small, they have significant population-level implications, especially for children exposed to other toxic chemicals, such as lead or air pollution.
Are these findings relevant to fluoridated communities?
Critics claim that no IQ deficits have been found at water fluoride levels below 1.5 mg/L, but this is wrong. First, no obvious threshold has been established. Second, fluoride in water is only one source of exposure, and total fluoride intake must be considered for risk assessment. Urinary fluoride, a snapshot of total fluoride intake, has shown significant reductions in IQ in children at concentrations typically found in fluoridated communities.
For example, a Canadian study found that 25% of pregnant women in optimally fluoridated areas had urinary fluoride levels above 1 ppm, and 5% above 1.5 ppm. While some question the reliability of urinary fluoride measurements, they are widely used by epidemiologists to assess exposure to short-lived chemicals such as fluoride and arsenic.
Does fluoridation protect against caries?
It is time for a critical review of the benefits of fluoride. Update for 2024 A Cochrane review found little or no benefit from water fluoridation in studies conducted after 1975, when fluoride toothpaste became widespread. The effects of fluoride on caries prevention are primarily topical, not systemic, and do not provide any benefit until the teeth erupt.
Should you be worried?
Public health agencies must reevaluate fluoridation guidelines based on new evidence. Until then, consider these precautions:
- Pregnant women and young children: Avoid fluoridated water and other sources of fluoride, such as black tea.
- Infant formula: Use non-fluoridated water to mix formula; breast milk contains a minimal amount of fluoride.
- Children’s toothpaste: Use only a rice-sized amount of fluoride toothpaste and make sure that children do not swallow the toothpaste.
By taking these steps, you can reduce fluoride exposure during critical developmental periods.
Sarah Evans
Assistant Professor of Environmental Medicine and Climate Science at the Icahn School of Medicine at Mount Sinai who studies how human exposures in early life can affect behavior and cognition.
It is important to note that none of the studies included in the [NTP] meta-analysis was conducted in the United States, where the recommended concentration of fluoride in drinking water is 0.7 mg/L—more than 50% lower than the fluoride exposure measured in most of the communities studied. While more studies are needed to examine the effects of exposure to lower levels of fluoride, 2023 meta-analysis found no association between fluoride and child IQ in communities with drinking water levels similar to those in the US.
Although there are no studies to date that indicate the danger of the 0.7 mg/L fluoride most commonly found in US drinking water, it is estimated that 2.9 million Americans and 180 million people worldwide may be exposed to fluoride at levels above WHO guidelines due to the presence of high levels of natural fluoride in some areas. Individuals living in these areas may be at greater risk of exposure to levels that have been associated with reduced child IQ in the study. In addition, the inclusion of fluoride in dental products and treatments as well as its natural presence in some foods and beverages can lead to exposure above the daily recommendation. Comprehensive studies measuring individual exposure levels of the US population from all sources of fluoride are needed.
Although about three-quarters of the US water supply is fluoridated, the practice is not federally mandated and is under state or local control, so fluoridation practices vary widely across the country. For example, 99.9% of Kentucky residents receive fluoride in their drinking water compared to only 16% of New Jersey residents. Individuals who wish to know the level of fluoride in their drinking water should contact their water supplier. If you live in an area with high levels of fluoride from natural sources and if you are pregnant or have young children, it is possible to reduce your exposure to fluoride with reverse osmosis filtration. Bottled water is not regulated for fluoride or other contaminants and is generally not recommended. If you drink water from a public supply or a private well that does not contain fluoride, it is important to maintain good dental hygiene by using fluoride toothpaste and mouthwash and regular visits to the dentist.
The findings of this study will likely lead to an increase in the number of communities asking whether they should discontinue water fluoridation. Although there is some evidence that the rise of fluoride products and improved access to dental care has reduced the need for fluoridated water, several studies show a dramatic increase in children’s cavities and the need for dental treatment in communities that have removed fluoride from drinking water, suggesting that fluoridation water remains an effective and necessary public health intervention.
While a recent meta-analysis by Taylor et al. suggests adverse effects of high levels of fluoride exposure on brain development, also emphasizes the need for well-designed longitudinal studies that measure fluoride exposure at the individual level over time to confirm whether there are associations with IQ or other neurodevelopmental outcomes at the low levels experienced by most Americans . In addition, it highlights the need to investigate practices that reduce the risk of fluoride exposure above recommended levels in areas where naturally occurring levels of fluoride are high and to review practices that increase access to routine dental care.