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Australian study of fluoridation neurotoxicity: Streetlight Effect Fallacy
Researchers looked in the wrong place. Couldn’t find IQ loss that other studies found.
Insensitive And Unreliable Measures Of Neurotoxicity
A just-published Australian study claims to have found no link between fluoridation and harm to children’s developing brains but didn’t use any IQ tests [Do 2022]. Instead, it used parent questionnaires of child behaviors which have been found to be relatively insensitive to detecting harm from fluoride and other neurotoxic chemicals.
The study’s lead author, dentist Dr. Loc Do of Queensland University, Australia, used two parent questionnaires to see if he could detect the same neurotoxic effects in Australian children that numerous other studies have found in Canada, Mexico, China, and elsewhere. But those studies all used standard IQ-type tests. Do’s study instead used a Strengths and Difficulties Questionnaire (SDQ), which is not a measure of intelligence or cognitive ability but is “a 25-item brief behavioral screening tool that measures children’s behaviors, emotions, and relationships.” For example, it asks parents whether their child can be described as “Kind”, “Lies”, “Bullied”, “Shares”, “Unhappy”, “Helps”, “Clingy”, and other items having little relationship to IQ [Ribeiro Santiago 2021].
Other Weaknesses: Ecological, Didn’t Account For All Fluoride Sources, Inadequate Control Of Confounders
Do’s study summary for his grant claimed his study would provide “high quality evidence” on fluoridation and intellectual development. However, it has additional important shortcomings compared to recent studies that found adverse neurotoxic effects. Do’s study, instead of using an individual-level measure of fluoride exposure, used a group-level measure (also called an ecological measure), and only tried to account for fluoride from fluoridated water, rather than all sources. This is an important weakness compared to the best studies, which either used the biomarker of urine fluoride concentration which reflects fluoride exposure from all sources, or used combined estimates of fluoride intake from drinking water and tea [Goodman 2022, Cantoral 2021, Farmus 2021, Wang 2021, Yu 2021, Zhao 2021, Till 2020, Wang 2019, Green 2019, Riddell 2019, Bashash 2018, Bashash 2017, Valdez-Jimenez 2017]. Tea has been found to be the second largest source of fluoride exposure after fluoridated water, even in a country with much lower tea consumption than Australia [Helte 2021]. The inability to account for all sources of fluoride exposure in the Do study likely further reduced the study’s ability to detect an effect of fluoride.
Another weakness of the Do study is its lack of control for potentially important confounders, which other recent studies did control for, including: lead, mercury, arsenic, PFOA, parent IQ, HOME score, gestational age, birth weight, parity, marriage status, smoking, alcohol use of mother, and Body Mass Index (BMI).
Cites Food & Pharma Industry Front-Group’s Bogus Review
More evidence of the author’s bias is found in the Do paper introduction that cites a very biased German review that concludes fluoride has no association with neurotoxicity [Guth 2020]. This is a favorite review of fluoridation defenders. But the authors of that review are closely associated with a front-group for food and pharmaceutical interests that has a history of claiming chemical food additives, genetically modified foods, and even endocrine disrupting chemicals are no problem [USRightToKnow 2022, CorporateEuropeObservatory 2012, TestBioTech 2012]. We’ll have more on those authors and their links with industry in a future bulletin.
Do’s Advocacy For Fluoridation Reveals Bias
Finally, the choice to publish Do’s paper in the fluoridation-friendly Journal of Dental Research (JDR) instead of a journal specializing in neurotoxicity or environmental health, is further evidence the Do study is biased to avoid finding an adverse effect that might threaten fluoridation. JDR is sponsored by the International Association for Dental Research (IADR), which has had a long-standing official position supporting fluoridation and claiming it is “safe and effective”. In fact, the latest update of the IADR Position Statement on fluoridation was written by Dr. Do and has outdated and misleading information about adverse effects [IADR 2021].
The Streetlight Effect Fallacy may explain how this Australian study failed to find harm to the brain from fluoridation, but another proverb summarizes what appears to be the attitude of the researchers, and of all fluoridation defenders who are trying to deny the strong scientific evidence that fluoride harms brains: See no evil, hear no evil, speak no evil… about fluoridation.
Other Weaknesses: Ecological, Didn’t Account For All Fluoride Sources, Inadequate Control Of Confounders
Do’s study summary for his grant claimed his study would provide “high quality evidence” on fluoridation and intellectual development. However, it has additional important shortcomings compared to recent studies that found adverse neurotoxic effects. Do’s study, instead of using an individual-level measure of fluoride exposure, used a group-level measure (also called an ecological measure), and only tried to account for fluoride from fluoridated water, rather than all sources. This is an important weakness compared to the best studies, which either used the biomarker of urine fluoride concentration which reflects fluoride exposure from all sources, or used combined estimates of fluoride intake from drinking water and tea [Goodman 2022, Cantoral 2021, Farmus 2021, Wang 2021, Yu 2021, Zhao 2021, Till 2020, Wang 2019, Green 2019, Riddell 2019, Bashash 2018, Bashash 2017, Valdez-Jimenez 2017]. Tea has been found to be the second largest source of fluoride exposure after fluoridated water, even in a country with much lower tea consumption than Australia [Helte 2021]. The inability to account for all sources of fluoride exposure in the Do study likely further reduced the study’s ability to detect an effect of fluoride.
Another weakness of the Do study is its lack of control for potentially important confounders, which other recent studies did control for, including: lead, mercury, arsenic, PFOA, parent IQ, HOME score, gestational age, birth weight, parity, marriage status, smoking, alcohol use of mother, and Body Mass Index (BMI).
Cites Food & Pharma Industry Front-Group’s Bogus Review
More evidence of the author’s bias is found in the Do paper introduction that cites a very biased German review that concludes fluoride has no association with neurotoxicity [Guth 2020]. This is a favorite review of fluoridation defenders. But the authors of that review are closely associated with a front-group for food and pharmaceutical interests that has a history of claiming chemical food additives, genetically modified foods, and even endocrine disrupting chemicals are no problem [USRightToKnow 2022, CorporateEuropeObservatory 2012, TestBioTech 2012]. We’ll have more on those authors and their links with industry in a future bulletin.
Do’s Advocacy For Fluoridation Reveals Bias
Finally, the choice to publish Do’s paper in the fluoridation-friendly Journal of Dental Research (JDR) instead of a journal specializing in neurotoxicity or environmental health, is further evidence the Do study is biased to avoid finding an adverse effect that might threaten fluoridation. JDR is sponsored by the International Association for Dental Research (IADR), which has had a long-standing official position supporting fluoridation and claiming it is “safe and effective”. In fact, the latest update of the IADR Position Statement on fluoridation was written by Dr. Do and has outdated and misleading information about adverse effects [IADR 2021].
The Streetlight Effect Fallacy may explain how this Australian study failed to find harm to the brain from fluoridation, but another proverb summarizes what appears to be the attitude of the researchers, and of all fluoridation defenders who are trying to deny the strong scientific evidence that fluoride harms brains: See no evil, hear no evil, speak no evil… about fluoridation.
