A new one report Linking fluoridated drinking water to lower IQ scores in children is sure to further fuel debate over what is considered one of these practices greatest achievements in public health of the 20th century.
The report, published Monday in JAMA Pediatrics, summarizes the results of dozens of research studies published since 1989. His general conclusion is that the more fluoride a child is exposed to, the worse they tend to perform on intelligence tests.
The analysis was carried out for US National Toxicology Programand it has attracted much criticism over the many years of its development. One of the biggest criticisms is that it is based on data from places where fluoride levels are far higher than the concentration recommended by law United States Public Health Service.
Adding fluoride to municipal drinking water has been cited as reducing the average number of teeth with decay by 44% in adults and 58% in adolescents since the 1960s. says the health service. But despite the proliferation of fluoride toothpastes and dental sealants, tooth decay is still a problem most common chronic disease It affects American children and the average senior is missing out at least 10 permanent teeth.
About 209 million Americans receive fluoridated water from their pipes, according to the Centers for Disease Control and Prevention. Robert F. Kennedy Jr., President-elect Donald Trump's pick to lead the Department of Health and Human Services, has said he would like to see that number fall to zero, in part because of concerns “IQ loss.”
The JAMA Pediatrics report is based on work prepared for the National Toxicology Program 324-page monograph on Fluoride and Brain Development, which was completed in August. Here's a closer look at what it shows – and what it doesn't.
Where does the data come from?
The report combines data from 74 studies on children's fluoride exposure and IQ. The majority of these – 45 – were carried out in China, with another 12 coming from India. None came from the United States, although three came from Canada and four from Mexico.
Ten of the studies were designed to do this Follow groups of people over time to see how their varying fluoride exposure affected IQ scores and other outcomes. The remaining studies examined fluoride exposure and the IQ of a population at the same time.
IQ scores were usually reported as averages for a group, although they sometimes reflected an individual's specific fluoride exposure.
How much fluoride are we talking about?
Fluoride exposure was measured in several ways.
Sometimes researchers measured the amount of fluoride in a community's drinking water, and sometimes they measured the amount of fluoride in participants' urine. Dental fluorosis – a condition that occurs when teeth receive too much fluoride and appear discolored – was also used to assess exposure. This also applies to environmental factors such as exposure to Pollution from coal burning with high fluoride content.
The studies were divided into three categories: those in which exposure was less than 4 milligrams of fluoride per liter of water (the maximum concentration approved in the USA by the Environmental Protection Agency); those where exposure was less than 2 mg/L (EPA's unenforceable regulations). secondary standard to prevent cosmetic problems in places where fluoride levels are naturally high); and those for whom exposure was less than 1.5 mg/L (the Guideline established by the World Health Organization).
So what is the connection with IQ?
Of the 65 studies included in the primary analysis, 64 found an inverse association between fluoride exposure and children's IQ – the higher (or lower) fluoride was, the lower (or higher) the IQ scores were.
The researchers also pooled data from nearly 21,000 children from 59 studies that reported average IQ scores. These data showed that children exposed to higher levels of fluoride had lower IQ scores than children exposed to lower levels of fluoride.
In addition, the report's authors combined data from 38 studies and calculated the numbers themselves to determine whether an overall dose-response relationship exists between fluoride and IQ. In fact, they wrote, “Lower children's IQ scores were associated with increasing fluoride exposure.”
That sounds bad. Should I be worried?
Not necessarily. The results are just so strong Because the data on which they are based and the studies in this analysis have some problems.
First of all, 52 of the 74 studies were deemed to be at “high risk of bias” by the report’s authors. This undermines the validity and reliability of their results.
Another problem is that in most studies, fluoride exposure was well above the U.S. target. Since 2015, the Public Health Service has established this “optimal” fluoride concentration at 0.7 mg/L, the equivalent of about 3 drops of fluoride in a 55 gallon drum. (Prior to this, the target value was between 0.7 and 1.2 mg/L.)
Only seven of the studies examined children whose water contained less than 1.5 mg/L fluoride. When considered alone, there was no association between fluoride exposure and IQ.
Also the American Academy of Pediatrics has noticed that assessing IQ in children is not a simple matter as measurements can be distorted by “socioeconomic, physical, familial, cultural, genetic, nutritional and environmental factors.” Comparing IQ scores from multiple studies in multiple countries as if they were the same only exacerbates the problem, the academy says.
Hmmm. What else should I know about this report?
A lot. In fact, JAMA Pediatrics published an editorial from Dr. Steven M Levya public dentistry expert at the University of Iowa to enumerate reasons why the report should not be taken at face value.
Take the problem of bias. Of the 59 studies that formed the core of the analysis, only 12 had a low risk of bias, and eight of them found no inverse association between fluoride and IQ, Levy wrote.
Then there is the use of urine to measure fluoride exposure. The report's authors called this a more precise way to measure a person's exposure to fluoride from all sources, not just drinking water. But this argument contradicts the “scientific consensus,” Levy wrote. Fluoride levels in urine vary significantly over the course of a day and from day to day There's no way to know whether a particular sample indicates a person's long-term exposure.
Levy also chastised the report's authors for cherry-picking the studies they included in their analysis. For example, given the selection of two publications based on data from the Canadian Study of Mother-Infant Research on Environmental ChemicalsThe report authors decided against the report that included postpartum fluoride exposure. They failed to publish it found no association between “fluoride exposure during pregnancy, infancy, or childhood and complete IQ,” he wrote.
Other recent, high-quality studies that showed no association also fell short, he added.
That's all?
There are further criticisms of the methodology and statistical analysis. However, one of Levy's biggest criticisms of the report is the “lack of transparency” of its backstory.
The authors downplayed the report's connection to the controversial monograph they prepared for the National Toxicology Program, Levy wrote. The first two drafts of this monograph received rigorous peer reviews from the National Academies of Sciences, Engineering and Medicine. The first version lacked clear evidence to support the authors' claim that “fluoride is likely to pose a threat to human cognitive neurological development,” and the second version glossed over the fact that it was unable to Shed light on the risks posed by fluoride low levels of fluoride in U.S. water systems, the NASEM evaluators said.
Levy wrote that the new report also does not mention that animal studies using fluoride levels equivalent to the U.S. standard of 0.7 mg/L found “no exposure-related differences in motor, sensory, or learning and memory performance” in nearly a dozen tests would have. as Researchers reported in 2018.
How can I tell if my water has fluoride added?
State and local governments decide for themselves whether to fluoride water supplies. In some places, the water is naturally rich in fluoride because much of it is found in the soil and bedrock. If the concentration is higher than 2.0 mg/L, the EPA requires authorities to notify people drinking this water within 12 months. If the concentration exceeds 4.0 mg/L, officials must notify the public within 30 days and take action to reduce fluoride to safe levels.
Nearly 63% of Americans receive fluoridated water, including the 3.5% whose fluoride levels are above optimal levels. according to CDC. If you want to see if your water system adds fluoride, give it a try Look it up on the CDC website. (Depending on where you live, you may need to contact your water provider directly.)
If you live in Los Angeles County, you can use: this card to see if you are among the 62% who receive “optimally fluoridated” water, the 5% whose water is “largely fluoridated,” the 22% whose water is “partially fluoridated,” or the 11 % whose water is not fluoridated.
That doesn't mean the water is fluoride-free: According to the Los Angeles Department of Water and Power, the city's groundwater contains fluoride at concentrations of 0.1 to 0.3 mg/L, and the water supplied by Los Angeles has fluoride levels Aqueduct range between 0.4 and 0.8 mg/L. All water supplied by the DWP is adjusted to a fluoride concentration of 0.7 mg/L. says the agency.
So what is the end result?
The report's authors acknowledged that their analysis was “not designed to consider the broader public health impacts of water fluoridation in the United States.” Still, they suggested that their findings “could influence future public health risk-benefit assessments of fluoride.”
A Second editorial The study accompanying the report said it raises enough questions to warrant a reassessment of the “potential risks of fluoride during early brain development.” The lack of a clear association between IQ scores and fluoride exposure below 1.5 mg/L “does not exonerate fluoride as a potential risk,” the editorial argued.
Levy disagreed. “There is no evidence of an adverse effect at the commonly used lower water fluoride levels” in U.S. water systems, he wrote. “Widespread use of fluoride for (cavity) prevention should continue.”