New Study Links Child Neurodevelopmental Deficits to Fluoridated Water in Calgary

A just-released study by University of Calgary researchers found “poorer inhibitory control and cognitive flexibility” in preschool children whose mothers were pregnant during times when the water was fluoridated in Calgary, Canada (Dewey 2023). The authors said their tests measured “executive function deficits [that have been] consistently associated with behavioural and neurodevelopmental disorders such as ADHD, autism spectrum disorder (ASD), intellectual disability, and specific learning disorders”. Executive dysfunction disrupts the ability to manage thoughts, emotions, and actions, including the ability to pay attention, solve problems, listen, and multitask.

The researchers took advantage of a “natural experiment” that arose during a three-year recruitment period of pregnant mothers for a study of how early life exposures affect child development. During the first two years of enrollment Calgary’s water was artificially fluoridated, but in the last year of enrollment fluoridation had been stopped. Enrollment lasted from 2009 to 2012 and fluoridation ceased in May 2011. Some pregnancies occurred entirely during the fluoridated period, and others entirely after fluoridation had ceased. The group of children born to “fluoridated” mothers had worse executive function scores than the group born later to “non-fluoridated” mothers. The adverse effects seemed to be worse in girls than boys.

A graphical abstract that summarizes the study:

From Fluoride Action Network article

IQ tests were also administered, but no differences were found in mean IQ between the fluoridated and non-fluoridated groups. Two study limitations might explain the lack of association between fluoride and IQ. First, Calgary has a natural water fluoride concentration as high as 0.4 mg/L which may not have been sufficiently different from the concentration during artificial fluoridation to cause a significant variance in IQ. The study did not attempt to determine the water fluoride concentration, but nationwide studies have found the fluoride concentration in artificially fluoridated Canadian cities averages about 0.6 mg/L (Green 2019, Table 1).

Another limitation, noted by the authors, is that the study did not use individual-level measures of exposure, such as the mother’s urine fluoride levels during pregnancy. Thestrongest studiesto date in North America have used individual urine fluoride measurements and have consistently found associations with reduced IQ (Bashash 2017Green 2019Till 2020).

The researchers concluded that their findings of executive function deficits, along with previous research, suggested “a possible need to reduce maternal fluoride exposure during pregnancy.” Supporting this suggestion, the authors noted systematic reviews had found “there is no benefit of … fluoride during pregnancy for the prevention of dental caries in offspring.”

Discussing the implications of their findings for the risk of ADHD, the authors cite another Canadian study byRiddell et al. (2019)that used nationwide data collected by Health Canada and found a 600% increased risk of ADHD diagnosis in adolescents per 1 mg/L increase in water fluoride. Evidence is mounting that fluoride’s neurotoxicity doesn’t just reduce children’s IQ, as found by the recent National Toxicology Programreportin 52 of 55 studies. The effect of fluoride on the developing brain may also cause behavioral difficulties, including those associated with ADHD.

Ironically, this new study is being released a year and a half after Calgary City Council voted to re-start fluoridation following a ten-year respite. The City Council had beenwarned by expertsabout the neurotoxic risks, including by William Ghali, MD, MPH, whopresented findingsfrom the University of Calgary’s own O’Brien Institute review of fluoride brain studies, and by FAN’s Paul Connett, PhD.

But fluoridation has not yet restarted in Calgary. There is still time for residents to realize they were misled by an aggressive campaign that dismissed the rapidly emerging science finding fluoride is neurotoxic, including at the levels used to fluoridate Calgary. More information on the Calgary fight is available from the local group,Safe Water Calgary.

Chris Neurath

Research Director
Fluoride Action Network