Canadian researchers recently released the results of a study on maternal fluoride exposure during pregnancy and IQ scores in young children between 2008 to 2011[1].
A finding of the study, published in JAMA Paediatrics, has sparked discussion among members of the community - that an increase in maternal urinary fluoride of 1 milligram per litre was associated with a 4.5-point IQ decrease in Canadian boys of 3-4 years of age.
This finding should be interpreted with extreme caution. Australian and international experts have questioned the validity of the methods used by the researchers and the strength of results reported.
The study was observational, meaning that it looked at an association between maternal urinary fluoride levels and IQ scores in young children but did not test a causative link between the two.
The study also found there was a statistically insignificant increase in IQ scores in girls of the same age where maternal urinary fluoride concentrations were one milligram per litre or more – a finding which casts doubt on causative inferences.
While the researchers did account for some confounding factors which could impact IQ scores, such as maternal education, employment and certain health conditions, many other factors known to impact brain development were not accounted for by the study, such as maternal alcohol intake, breastfeeding practices and nutritional intake in the early years of life. The accuracy of the methods used by the researchers to estimate fluoride intake are also untested, as no external validation of these methods has been carried out.
It is important to consider this new study in line with the overwhelming weight of existing scientific evidence that shows fluoride is safe and beneficial in reducing tooth decay.
Extensive evidence shows there is no connection between levels of fluoride in drinking water and IQ in children. Two recent studies in New Zealand[2] and Sweden[3] looked at the same question as the Canadian researchers and found no association between water fluoridation and IQ scores.
The National Health and Medical Research Council in 2017 conducted an extensive review of evidence on the health effects of water fluoridation, informed by an expert panel of highly-regarded specialists. The review found reliable evidence that community water fluoridation as practised in Australia is not associated with health problems – including cognitive dysfunction and lowered IQ[4].
The weight of rigorous research evidence is clear – community water fluoridation at current Australian levels is a safe, effective and ethical way to reduce tooth decay.
Dental Health Services Victoria continues to support water fluoridation as a fair way of delivering the benefits of fluoride to the community, regardless of individual age, education, income or motivation.
More information on Victoria’s water fluoridation can be found at https://www2.health.vic.gov.au/public-health/water/water-fluoridation/fluoride-information
[1] Green, R, Lanphear, B, Hornung, R, Flora, D, Martinez-Mier, EA, Neufeld, R, Ayotte, P, Muckle, G & Till, C 2019, ‘Association Between Maternal Fluoride Exposure During Pregnancy and IQ Scores in Offspring in Canada’, JAMA pediatrics.
[2] Broadbent, J.M., Thomson, W.M., Ramrakha, S., Moffitt, T.E., Zeng, J., Foster Page, L.A. and Poulton, R., 2015. Community water fluoridation and intelligence: prospective study in New Zealand. American journal of public health, 105(1), pp.72-76.
[3] Aggeborn, L. and Öhman, M., 2017. The effects of fluoride in the drinking water (No. 2017: 20). Working Paper: IFAU Institute for Evaluation of Labour Market and Education Policy.
[4] NHMRC (National Health and Medical Research Council) 2017. NHMRC Public Statement 2017 - Water Fluoridation and Human Health in Australia. Canberra: NHMRC.