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There are strong Canadian connections with most of the following studies. Christine Till, who was the lead author of both the Green and Till studies, teaches at York University; Bruce Lanphear (co-author of the Green and Till studies), an American citizen who teaches at Simon Fraser University in Vancouver; and Howard Hu, the lead author of the Bashash studies, who did his research at the University of Toronto for many years.

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July 2024: PKC-θ is an important driver of fluoride-induced immune imbalance of regulatory T cells/effector T cells – This Chinese study explored the mechanism of fluoride interference in the immune system and the key indicators of fluoride-induced immune damage. It represents the first evidence suggesting that Protein Kinase C-θ (PKC-θ) may be the key to immune imbalance in the body under fluoride exposure.


May 2024: Maternal Urinary Fluoride and Child Neurobehavior at Age 36 Months – This study published in JAMA Network Open found that prenatal fluoride exposure may increase the risk of neurobehavioral problems among children living in an optimally fluoridated area in the United States.  A 0.68 mg/L increase in maternal urinary fluoride during pregnancy was associated with nearly double the odds of borderline clinical or clinical neurobehavioral problems.


January, 2024, The LOTUS Study – With 6.4 million study subjects, this is the largest fluoride study ever conducted. Its aim was to determine the effectiveness and cost-effectiveness of water fluoridation for adults and adolescents. Over 10 years, people receiving optimally fluoridated water experienced only a 2% reduction in the number of decayed, missing, and filled teeth, compared to those whose water was not fluoridated. The study found NO meaningful benefit to water fluoridation, nor any compelling evidence that water fluoridation reduced social inequalities in dental health.  [WATCH VIDEO -1:37 minutes]


January 2024: Fluoride exposure and thyroid hormone levels in pregnancy – This is the first study to investigate sex differences in the association between fluoride exposure and maternal thyroid hormone levels in pregnancy. It found that 1 mg/L increase in urinary fluoride was associated with a 35% increase in thyroid stimulating hormone (TSH) among women pregnant with girls. Urinary fluoride concentration is an objective biomarker of short-term fluoride exposure. It allows for more precise estimates of fluoride intake from multiple sources.

*The MIREC Study, which started in 2007, is an ongoing study to examine the effects of prenatal exposure to environmental chemicals on the health of pregnant women and their infants.

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November 2023: Systematic review of epidemiological and toxicological evidence on health effects of fluoride in drinking water – This Canadian study identifies both dental fluorosis and reduction in children's IQ scores as key endpoints for establishing a health-based value (HBV) for fluoride in drinking water. The authors state that neurodevelopmental cognitive effects may warrant special consideration in determining HBV. They suggest a “point of departure” of 1.56 mg/L for fluoride in drinking water for establishing a reference dose and public health safety guidelines, based only on the lowest-observed-adverse-effect level (LOAEL) for moderate and severe dental fluorosis. They do not address the potential impact on IQ scores.


September, 2023 – A 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. 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.


Till et al., April 2023 – Professor Christine Till and PhD student Meaghan Hall found an association between fluoride exposure from tap water and hypothyroidism in pregnancy. They say this latest study may explain an earlier study looking at maternal fluoride exposure in pregnancy and lower IQ in boys.  “The findings are concerning because hypothyroidism is a known cause of brain-based disorders in children,” says Till. Hall and Till say they hope that policy makers will consider this new research when evaluating the safety of community water fluoridation


Well-designed prospective cohort studies funded by both the National Institute of Environmental Health Sciences [NIEHS] in the USA as well as Health Canada, have shown a loss of IQ and increased symptoms of ADHD in offspring when pregnant women are exposed to fluoride at doses commonly experienced in fluoridated communities in Canada (Bashash, 2017, 2018 and Green, 2019).  The consequences are shocking!  According to Dr. Philippe Grandjean, from Harvard University, “Fluoride is causing a greater overall loss of IQ points today than lead, arsenic or mercury”, as detailed in this risk analysis.


Till et al., 2020 have shown a large reduction in IQ when children were bottle-fed as babies in communities which were fluoridated, compared with babies who were bottle-fed in non-fluoridated communities.


According to Linda Birnbaum, Ph.D., former Director of the U.S. NIEHS (2009-2019) and two leading public health researchers (Bruce Lanphear, MD, MPH, and Christine Till, PhD) who authored two key fluoride-IQ studies (Green, 2019 and Till, 2020), ingestion of fluoride during pregnancy confers no dental benefit to the fetus, so this is a situation where risks are being taken for no proven benefit (see their editorial published in Environmental Health News, Oct 7 2020).

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An important well-conducted study from Sweden has shown an increased prevalence of hip fracture in post-menopausal women associated with long term exposure to natural fluoride at levels in water in the same range as Canada fluoridates its water [Helte et. al., 2021].  This is very serious because, as you probably know, hip fractures in the elderly are debilitating, costly to treat, lead to a loss of independence and often shortens the life of those impacted.  This finding also underlines the fact that fluoride can impact our health over a whole lifetime of exposure.


These icons will reveal the following scientific studies from the years 2000 and 2015: 

  • A letter from the chair of the advisory panel for the year 2000 British York Review followed by the complete review which at the time was considered the most rigorous and respected scientific review on the effects of water fluoridation.

  • A summary of the year 2015 Cochrane review on the effects of water fluoridation.

    NOTE: The Cochrane Review, the 2000 York Review, and the 2006 US National Academies of Sciences National Research Council's 3.5 year review are the only independent systematic reviews ever done on the scientific research looking at the effects of fluoride in drinking water. This makes these reviews the most rigorous & least biased. Further descriptions about systematic reviews are offered on the Making Sense of the Science page.

From 2015 to current:

  • Brenda Staudenmaier is a Plaintiff in the US lawsuit against water fluoridation and maintains on her website a “sampling” of the scientific studies and reports relevant to water fluoridation published since the US Department of Health & Human Services (HHS) 2015 recommendation to lower the fluoridation target to 0.7 ppm.

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