Swedish study finds fluoride in drinking water affects children’s health

Fluoride occurs naturally as fluoride ions in drinking water, but levels are low in municipal drinking water in Sweden. In some countries such as the USA, Canada, Chile, Australia and Ireland, it is common to add fluoride to municipal drinking water to prevent caries, usually at around 0.7 mg fluoride per litre of water. In Sweden, fluoride is never added to municipal drinking water, but high fluoride levels can occur in rock-drilled wells.

“The addition of fluoride to drinking water is controversial due to concerns about health risks. Our findings support the hypothesis that even relatively low levels of fluoride may have negative effects on children’s early development,” says Maria Kippler, associate professor at the Institute of Environmental Medicine, Karolinska Institutet (KI), in a press release. Researchers have investigated the link between early exposure to fluoride and children’s cognitive abilities. The study included 500 mothers and their children in rural Bangladesh, where fluoride occurs naturally in drinking water. The levels are consistent with those found in Sweden and many other countries, according to the researchers.

Swedish water

In the study, trained psychologists evaluated the children’s cognitive abilities at the ages of five and ten using well-established tests. The mothers’ and children’s exposure was determined by measuring fluoride in urine samples, which reflects ongoing exposure from all sources such as water, food and improperly used dental care products, KI states. “I would like to emphasize that dental products such as toothpaste are not normally a significant source of exposure because they are not intended to be ingested. Fluoride in toothpaste can prevent caries, but it is important to teach even young children to spit out the toothpaste after brushing their teeth”, says Maria Kippler.

Lower cognitive abilities

The median value for fluoride in the urine of pregnant women in Bangladesh was 0.63 mg/L. Higher fluoride levels in pregnant women were linked to increasingly lower cognitive abilities in their children at the ages of five and ten. Children who had more than 0.72 mg/L fluoride in their own urine at the age of ten also had poorer cognitive abilities than children with lower fluoride levels in their urine. It was particularly the children’s verbal comprehension and their ability to interpret and process sensory impressions that were affected.

Legal fluoride limitations

The exposures that showed an association with poorer cognitive development are lower than the EU’s existing limit values. In the European Union, the legal limit is 1.5 milligrams per litre (mg/L).  ​​The researchers found no statistically significant link between fluoride levels in the urine of five-year-olds and their cognitive abilities. “This could be due to the shorter exposure, but also because the measurements are not as reliable in younger children due to greater variations in how fluoride is absorbed and accumulated in the body, especially in the skeleton”, says Maria Kippler.

More research is needed

Because it is an observational study, it is not possible to draw firm conclusions about causality, the researchers state. Therefore, they believe it is important to assess the combined results from several similar studies. The European Food Safety Authority (EFSA) recently conducted a public consultation to draft a scientific opinion on updated consumer risk assessment of fluoride in food and drinking water including the contribution from other sources of exposure.  The Karolinska Institute will now continue to investigate the relationships in other populations. They will also establish experimental models to investigate which molecular mechanisms could explain the relationships. “It is important to continue research that can form the basis for assessing appropriate limit values ​​for fluoride. Even small changes in cognition at the population level can have major consequences for public health “, concludes Maria Kippler. The study was mainly funded by Formas and the Swedish Research Council. The researchers declare that there are no conflicts of interest.

This article was published first on the Swedish platform for water professionals cirkulation.se

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