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Children with chronic exposure to high levels of fluoride in drinking water made more errors on drawing and cognitive tests, according to a new pilot study by researchers at Tulane University.
The study, which linked fluoride exposure and cognitive impairment, was published in the November-December issue of the peer-reviewed Neurotoxicology and Teratology journal.
Lead author Tewodros Godebo, Ph.D., assistant professor of environmental health sciences at Tulane University School of Public Health and Tropical Medicine, told Tulane News that the testing underlying their study “affirmed a clear association between high fluoride and cognitive impairment.”
“These results add to the growing concern about the potential neurotoxic effects of fluoride, especially during early brain development and childhood,” Godebo said. He said more epidemiological studies should be conducted to validate the findings of his team’s work.
For the study, researchers recruited 74 children ages 5-14 from demographically and ethnically similar rural Ethiopian farming communities with varying levels of natural fluoride in their community wells, ranging from 0.4 to 15.5 mg/L.
The U.S. Public Health Service recommends 0.7 milligrams per liter (mg/L) as the “optimal level” for water fluoridation and the World Health Organization recommends that fluoride levels be kept below 1.5 mg/L.
The children were tested for fluoride exposure and their cognitive performances were measured using two tests.
One test assessed the children’s abilities to draw common objects. The other used the Cambridge Neuropsychological Test Automated Battery, or CANTAB test, to assess memory and learning.
The researchers didn’t analyze IQ. Instead, they used tests designed to identify different markers of cognitive impairment and found that the higher the levels of fluoride exposure, the worse children performed on both tests and that in the CANTAB tests, the total number of errors became “markedly stronger” as the tasks became more difficult.
“This well-conducted study by a team of U.S. scientists is the latest in a long series of studies showing that fluoride is a neurotoxicant that can cause cognitive impairment in children,” Michael Connett, attorney for the plaintiffs in a lawsuit challenging the U.S. Environmental Protection Agency (EPA) to end water fluoridation in the U.S.
“At this point, it’s no longer a question of, does fluoride damage the brain? Does fluoride lower IQ?” Connett told The Defender. “It’s a question of, at what dose? How does that dose vary with innate susceptibility among the population?”
He added, “The obliviousness of public health officials to this clear and present danger is becoming intolerable.
Fluoride exposure is receiving more scrutiny from scientists and the public in part because of a lawsuit brought in 2017 by Food and Water Watch, Fluoride Action Network and others alleging water fluoridation violates the EPA’s Toxic Substances Control Act and that fluoride is neurotoxic and lowers children’s IQ.
Numerous recent scientific studies have linked fluoride exposure to cognitive impairment in children, including reduced IQ. Although some studies have not found similar associations.
Epidemiological studies have also shown specific links to reduced IQ and other cognitive effects on children in areas with high endemic levels of fluoride in drinking water supplies.
The authors of the Tulane study called for more research on the topic, particularly for studies to establish at what level fluoride is neurotoxic, as well as the effects of low levels of fluoride in drinking water.
Higher exposure ‘consistently associated with lower IQ’
The Tulane study’s findings support similar findings released — by court order as part of the lawsuit against the EPA — by the National Toxicology Program (NTP) in March in a draft report linking prenatal and childhood fluoride exposure to reduced IQ in children.
Public health officials tried for almost a year to block its publication, documents obtained by plaintiffs through the Freedom of Information Act revealed.
The NTP — which operates under the U.S. Department of Health and Human Services National Institute of Environmental Health Sciences and analyzes environmental toxins — conducted a six-year systematic review to assess scientific studies on fluoride exposure and potential neurodevelopmental and cognitive health effects in humans.
The report, a monograph and a meta-analysis of existing studies on fluoride’s neurotoxic effects concluded that “higher fluoride exposure is consistently associated with lower IQ in children.’”
The findings from the report will inform the next phase of the trial set to begin at the end of January.
Study will inform growing controversy over water fluoridation
The Tulane study was conducted in the Main Ethiopian Rift Valley, where there are well-known endemic high levels of fluoride exposure. Researchers selected eight rural communities with high naturally occurring fluoride in their community wells.
Children in the study were born and raised in the villages that used the wells and had been chronically exposed to elevated fluoride levels since conception.
Researchers estimated the daily fluoride intake for each child based on their water intake and the fluoride concentration in the water relative to their size. They took urine samples from the children in order to determine their fluoride exposure.
Then they asked the children to use a pencil and eraser to draw three common objects — a house, a person and a donkey — they encountered on a daily basis, using as much time as they needed. The researchers then evaluated the drawings.
Researchers also tested the children using the CANTAB Paired Associate Learning test, which tests spatial memory and learning linked to the medial temporal lobe, the brain region thought to be most affected by fluoride toxicity.
They found a clear association between high levels of fluoride in drinking water and cognitive impairment. The study notes that these levels exceeded the EPA’s no-observed-adverse-effect-level for fluoride.
Figure 2. Representative children’s drawings of a donkey for children in different fluoride exposure groups. The figures were selected by averaging the scores at each community and picked a drawing close to the mean score. Note that the label on each figure represents water concentration of fluoride (mg/L)/drawing score. Credit: Tewodros Rango Godebo Ph.D. et al.
Higher exposure was linked to more errors in their drawing scores for the donkey, house and person.
Similarly, for the CANTAB tests, they found that increased levels of fluoride in drinking water were strongly associated with increased errors made by children and that the effects became more pronounced as the level of task difficulty increased.
This and further studies are key, the authors concluded, to develop policies to mitigate environmental exposure to fluoride and to “inform the growing controversy over the safety of water fluoridation.”
