The Letter of Concern sent to the IRB members
The concerns to the serious problems of this experiment are enumerated in this first of four letters sent to the members of the Institutional Review Board (IRB).
The letter was signed by Paul Connett, PhD, Executive Director, American Environmental Health Studies Project (AEHSP) and the Fluoride Action Network (FAN). To date, no acknowlegment of the receipt of the letter, or a response to the concerns expressed, have been received. There was one email to inform Dr. Connett that one member of the IRB he had written to was no longer involved. Letter also in pdf format.
March 14, 2022
Letter to: Univ. of North Carolina Chapel Hill, Office of Human Research Ethics (OHRE), Office of Director; Institutional Review Board (IRB); and IRB Compliance Office
John Roberts OHRE Director’s Office <email@example.com>
Louise Winstanly IRB B Chair <firstname.lastname@example.org>
Robert Matthews IRB D Chair <email@example.com>
IRB Compliance Office <firstname.lastname@example.org>
RE: Concerns about IRB ethical evaluation of “waterBEST” study
Dear OHRE Director, and Chair and members of the IRB:
We wish to bring to your attention serious concerns about a proposed human research study that we understand you are currently evaluating.
The study name is “Phase II, proof-of-concept randomized controlled trial to evaluate dental caries preventive effects of fluoridated bottle water” and the Principal Investigator is Dr. Gary Slade. The University of North Carolina, Chapel Hill, is the awardee for the funding of this project. Another name for the project is “Water From Bottles to Establish Strong Teeth (waterBEST)”.
Information on the project proposal is available from these websites:
NIH project number: 4UH3DE029169-02
The project’s website:
The concerns with this study arise under five of the Guiding Principles for Ethical Research set forth by the National Institutes of Health (NIH), available at these websites:
https://www.nih.gov/health-information/nih-clinical-research-trials-you/guiding-principles-ethical-research and https://www.cc.nih.gov/recruit/ethics.html
The five principles we believe this study may violate are:
• Favorable risk-benefit ratio
• Informed consent
• Fair subject selection
• Scientific validity
Favorable risk-benefit ratio
The NIH Guideline requiring a Favorable risk-benefit ratio states:
Everything should be done to minimize the risks and inconvenience to research participants to maximize the potential benefits, and to determine that the potential benefits are proportionate to, or outweigh, the risks.
In the information available at the clinicaltrials.gov website, at the NIH’s reporter.NIH.org website, and at the project’s own waterBESTstudy.org website, there is no mention of any risks. There are also no quantitative estimates of the benefits which are only described as “uncertain”.
The study protocol and documentation seem to have excluded mention of the strong evidence that early life fluoride exposure poses a serious neurodevelopmental risk. The National Research Council (NRC) first drew attention to this concern in 2006 in an extensive review of fluoride toxicity [NRC 2006]. The NRC recommended new rigorous research be conducted on this question. Responding to that recommendation, NIH has funded several such studies that confirmed the earlier studies finding adverse neurodevelopmental effects, including reduced IQ and greater risk of ADHD in children. In light of the accumulating evidence, in 2015 the National Toxicology Program (NTP) of NIEHS/NIH commenced a comprehensive systematic review of studies of fluoride developmental neurotoxicity. The NTP’s literature search identified 159 relevant human epidemiological studies and over 300 animal studies. A large majority of the epidemiological studies found statistically significant adverse effects, such as reduced IQ. The NTP rated 27 of the studies as being of high quality (low risk of bias). Of these 27 studies, 25 found statistically significant adverse neurobehavioral effects, and 15 were at exposure levels the NTP considered directly applicable to exposures from artificially fluoridated water [NTP 2020, Neurath 2020a, Neurath 2020b].
The studies identified by NTP are remarkably consistent in finding large magnitude adverse effects. The size of the IQ losses has been described by experts, including the editor of JAMA Pediatrics as “on par with that from lead” [Christakis & Rivara 2019]. A meta-analysis conducted by the NTP of 49 studies found a pooled estimate of -7 IQ points for the children with higher fluoride exposure compared to the children with lower exposure.
One of the higher quality studies is especially relevant to the proposed waterBEST study because it focused on fluoridated water exposures in the same infancy age range as waterBEST proposes to recruit from [Till 2020]. This NIH-funded study was of a Canadian cohort and found that amongst infants who were primarily formula-fed with formula made up from tap water, the loss of IQ was -4.4 IQ points for each 0.5 mg/L increase in water fluoride concentration. The waterBEST study description at clinicaltrials.gov says the treatment group of children, who will be recruited between 2 and 6 months of age, will receive water with a fluoride concentration of 0.8 mg/L. These children therefore risk losing an average of -7 IQ points. Furthermore, several recent studies have found that children with certain genetic variants may experience 5x greater loss of IQ from fluoride than the average loss in children who do not have those variants. These more susceptible children would be at risk to potentially lose -35 IQ points, an extremely severe permanent adverse effect [Zhang 2015, Cui 2020, Wang 2021, Zhao 2021]. But even a loss of 7 IQ points is very serious and has been estimated by economists as being associated with a lifetime loss of earnings of about $140,000 per person [Grosse 2007].
The magnitude of these neurodevelopmental risks is out of all proportion to any possible dental benefits the waterBEST study intends to investigate. This study therefore violates any prudent interpretation of having a “Favorable risk-benefit ratio”.
The only mention of possible neurodevelopmental risk from early life fluoride exposure found in the publicly available materials about the waterBEST study comes from a “fact sheet” linked from the waterBest.org website, titled “Community Water Fluoridation”. But instead of providing any scientific information, it dismisses the risk with a blanket statement claiming a lack of scientific evidence, referencing reports that are more than 16 years out of date:
No convincing scientific evidence has been found linking community water fluoridation (CWF) with any potential adverse health effect or systemic disorder such as … low intelligence … 4, 6.
References 4 and 6 are from 2000 and 2006. They did not consider the NRC 2006 review, the current NTP systematic review, or the dozens of high quality studies published since 2006 [most recently: Zhou 2021, Zhao 2021, Yu 2021, Farmus 2021, Till 2020, Cui 2020, Wang 2020, Green 2019, Riddell 2019, Bashash 2018, Bashash 2017, Valdez Jiménez 2017].
The Declaration of Helsinki states that “Medical research involving human subjects must … be based on a thorough knowledge of the scientific literature” [World Medical Association 2013]. Given the lack of any mention of the risk of neurotoxicity in the waterBEST study materials, it appears this project is not based on a thorough knowledge of the scientific literature of fluoride risks.
In a legal deposition, under oath, Principal Investigator Dr. Gary Slade acknowledged that he was not an expert in any non-dental effects of fluoride and had never conducted any original research on any adverse effects, including neurotoxicity. He also acknowledged he had never done original research on dental effects of fluoride exposure during the first year of life. He also stated he was not an expert on risk-benefit assessment and would not undertake to assess the risk-benefit ratio between dental benefits and neurodevelopmental harms [Slade deposition 2019, see Appendix A below].
In his deposition, Dr. Slade also acknowledges several reasons for the uncertainty of dental benefits from fluoridated water. He acknowledges that very few studies have ever been blinded, that none of his own studies of fluoride and dental caries have used blinding, that lack of blinding can introduce bias in the direction favored by the researchers, and that no RCT has ever been done with fluoridated water [Slade deposition 2019, see Appendix B below].
Based on the information available to us, it appears Dr. Slade has neither attempted to assess the risk-benefit ratio of neurodevelopmental harm against reduced dental caries, nor attempted to acquire “a thorough knowledge of the scientific literature” on the risks, as required under the Declaration of Helsinki principles. His lack of expertise in non-dental effects of fluoride and his acknowledgement that he is not qualified to do risk-benefit assessments are not acceptable excuses for the apparent absence of one in his study proposal.
The lack of any mention of neurotoxic risks raises serious concerns about whether the waterBEST study meets the NIH Guidelines for Informed Consent:
Potential participants should make their own decision about whether they want to participate or continue participating in research. This is done through a process of informed consent in which individuals (1) are accurately informed of the purpose, methods, risks, benefits, and alternatives to the research, (2) understand this information and how it relates to their own clinical situation or interests, and (3) make a voluntary decision about whether to participate. [emphasis added]
We have requested the Informed Consent form from Dr. Slade but have not yet received a copy. Based on the publicly available information about the waterBEST study, we are concerned the proposal has little or no accurate information about the potential neurodevelopmental risks to participating children.
We are also concerned that in a published article about public messaging to improve chances of winning local political referendums on water fluoridation, Dr. Slade, the senior author, says:
Given that the average person does not understand fluoridation scientifically … mixed messages that introduce even some uncertainty should be enough to lead to a rejection at the polls.” [Curiel 2018].
Based on this statement by Dr. Slade, we are concerned that if he was asked to accurately inform participants of the neurodevelopmental risks of his study, he might choose to avoid “mixed messages” and downplay the evidence for risks, so as to limit rejections of participation.
The NIH Informed Consent guideline also requires that the consent be given voluntarily. The waterBEST study proposes to recruit participants from an area with a high proportion of people living in poverty and with a high proportion of Blacks and Hispanics. The proposed study would give participants free annual dental exams, free home-delivered bottled water for 3½ years, a water cooler, shelves for water bottles, infant bottles, sippy cups, and $480 in cash compensation. These inducements bring into question whether participation will be entirely voluntary, or whether some in this vulnerable population may agree to participate because of the substantial, for them, financial and health care inducements.
Fair subject selection
The primary basis for recruiting participants should be the scientific goals of the study — not vulnerability, privilege, or other unrelated factors. [NIH ethics guidelines]
The issue of the vulnerability of participants, although not elaborated on in this summary, is the underlying impetus to all research ethics rules and guidelines. The NIH website says:
The ethical guidelines in place today were primarily a response to past abuses, the most notorious of which in America was an experiment in Tuskegee, Alabama, in which treatment was withheld from 400 African American men with syphilis so that scientists could study the course of the disease. Various ethical guidelines were developed in the 20th century in response to such studies. [NIH ethics website]
The Lenoir County NC population is more than 50% non-white, with 40% Black, 8% Hispanic, and 3% other non-white [censusreporter.org]. This puts Lenoir County in the top rankings for percentage Black population amongst North Carolina counties. The percent of persons below the poverty line is 22%, which is also in the top rankings in North Carolina.
The inducements of free annual dental exams, free home-delivered bottled water for 3½ years, a water cooler, shelves for water bottles, infant bottles, sippy cups, and $480 in cash compensation would likely exceed a value of $1000 per participant. The offer of free annual dental exams is also a substantial inducement in a population that may otherwise have great difficulty in obtaining this basic health service.
The community chosen for this study can be considered to be vulnerable because of race, poverty, and because they are infants and young children. The financial inducements may further compromise the ethical guideline requirement that participation be completely voluntary.
The Declaration of Helsinki says “All vulnerable groups and individuals should receive specifically considered protection” [World Medical Association 2013].
Instead of special protection, there is the appearance this group was selected by the researchers because its vulnerabilities might make for easier recruitment of participants, a direct violation of the ethical principle of Fair subject selection.
We have serious concerns for Dr. Slade’s objectivity, which is a requirement under the NIH Guideline principle of Independent Review. NIH describes the key factors to consider during Independent Review:
To minimize potential conflicts of interest and make sure a study is ethically acceptable before it starts, an independent review panel should review the proposal and ask important questions, including: Are those conducting the trial sufficiently free of bias? Is the study doing all it can to protect research participants? Has the trial been ethically designed and is the risk–benefit ratio favorable? The panel also monitors a study while it is ongoing. [emphasis added]
We believe Dr. Slade has serious conflicts of interest, including direct financial conflicts. In 2018 Dr. Slade was recruited as a paid expert witness in a civil lawsuit, the subject of which was the neurotoxic risks of water fluoridation. He was asked to testify on the dental benefits of water fluoridation. Dr. Slade reported being compensated at the rate of $100 per hour and had signed a contract with a total estimated fee of $22,400 for his work for the defendant in the case, the US EPA [Slade 2019 deposition transcript, see Appendix C below].
In addition to this paid work to help defend water fluoridation in a civil lawsuit, there is evidence of Dr. Slade’s bias in promotion of water fluoridation by his membership in the Scientific Advisory Board of the advocacy organization, The American Fluoridation Society. Under oath, in his deposition, Dr. Slade said he shared the goals of the American Fluoridation Society, which are to promote and extend fluoridation in the USA, including by means of lobbying in local political campaigns [Slade 2019 deposition transcript, see Appendix D below]. Dr. Slade himself participated in such lobbying to promote fluoridation in at least one instance, in Green Bay WI, where he defended fluoridation to local officials [archived video of public hearing, Green Bay WI, https://www.youtube.com/watch?v=zodhMbzoJf0 at 33:33 min:sec].
Additional evidence of bias is found in several papers co-authored by Dr. Slade, in the NIH grant application, and in the waterBEST website [Curiel 2018, Curiel 2019, NIH Reporter.org, waterBEST.org]. The NIH grant application summary justifies the study as a way to try to extend fluoridated water use in the USA:
[Fluoridation benefits] have never been tested in a randomized controlled trial (RCT). Instead … community intervention studies were sufficient to justify addition of fluoride to many public water systems … and to defend against fluoridation’s critics. However, growth in fluoridated public water systems has stalled, leaving 100 million Americans living in places that do not have fluoridated water….
An underlying assumption in this grant application is that fluoridation needs to be defended against its critics so that fluoridated water can be extended to more Americans. Dr. Slade does not appear to be an objective researcher balancing risks and benefits in the design of the waterBEST study. His goal appears to be a study which will help campaigns to extend the use of fluoridated water.
Finally, the proposed study has a fundamental weakness in terms of scientific validity. The placebo group’s water will come from a different water source than the treatment group’s water [clinicaltrials.gov]. Numerous minerals and contaminants in drinking water have been found or suspected to alter caries risk [Dogan 2018, Qamar 2017, Pathak 2016, Lippert 2013, Curzon 1978]. By not using identical water in the two groups, except for added fluoride, this study will not be able to rule out the possibility that any treatment-related effects are actually caused by some factor(s) other than fluoride. This violates basic RCT design principles.
We have very serious concerns that the waterBEST study and its Principal Investigator, Dr. Gary Slade, violate ethical guidelines for human research, as codified by NIH and other groups. The study proposes to recruit from a vulnerable population, and expose them to a substance at levels that have been found to pose a substantial risk of developmental neurotoxicity that may result in lowering the children’s IQ and other serious harms. The only conjectured benefit is a reduction in dental caries, of unknown magnitude. The NIH grant proposal acknowledges uncertainty of the “effect size of the intervention”:
… RCT evidence of dental health benefits of fluoridated bottled water will be essential if public health is to embrace it as a strategy to extend fluoridation. In the absence of a precedent, and in the face of uncertainty as to compliance and likely effect size of the intervention …. [NIH RePORTER] [emphasis added]
This quote also suggests an underlying agenda of the study is to try to provide support for “a strategy to extend fluoridation”.
We do not believe this study, in this age group, could ever meet ethical guidelines because of its highly unfavorable risk-benefit ratio. The risks are much worse than any conceivable dental benefits. Losing 7 IQ points to save any number of cavities is not an acceptable trade-off. Furthermore, the researchers themselves acknowledge the benefits are uncertain.
We request that you consider these serious problems with this project as soon as possible. We urge the IRB to immediately put the study on hold to prevent the risk of permanent harm to the children.
We would be happy to provide more information and would also welcome further discussion and the opportunity to meet with OHRE or the IRB on this matter.
We hope OHRE and the IRB will appreciate the seriousness of these concerns. We request a prompt response and acknowledgement of receipt of this notification.
Paul Connett, PhD
Executive Director, American Environmental Health Studies Project (AEHSP) and Fluoride Action Network (FAN)
Dr. Connett is a graduate of Cambridge University, with a doctorate in chemistry from Dartmouth College. He taught chemistry and environmental toxicology at St. Lawrence University for 23 years. His areas of expertise include: interaction of metals with biological systems (chromium, lead); build-up of dioxins in food chains; health risk assessment; the problems, dangers and alternatives to incineration; resource management for a sustainable society (Zero Waste); the toxicity of fluoride and the dangers of fluoridation. He is co-author of the book The Case Against Fluoride (2011). He has been invited to testify on fluoride toxicity before numerous government and scientific bodies, including the National Academies of Science.
1. Bashash M, Marchand M, Hu H, Till C, Martinez-Mier EA, Sanchezd BN, et al. Prenatal fluoride exposure and attention deficit hyperactivity disorder (ADHD) symptoms in children at 6-12 years of age in Mexico City. Environ Int [Internet]. 2018;121:658–66. Available from: https://doi.org/10.1016/j.envint.2018.09.017
2. Bashash M, Thomas D, Hu H, Angeles Martinez-Mier E, Sanchez BN, Basu N, et al. Prenatal Fluoride Exposure and Cognitive Outcomes in Children at 4 and 6–12 Years of Age in Mexico. Environ Health Perspect [Internet]. 2017 Sep 22;125(9):097017. Available from: https://ehp.niehs.nih.gov/doi/10.1289/EHP655
3. Choi AL, Zhang Y, Sun G, Bellinger DC, Wang K, Yang XJ, et al. Association of lifetime exposure to fluoride and cognitive functions in Chinese children: a pilot study. Neurotoxicol Teratol [Internet]. 2015;47:96–101. Available from: http://www.sciencedirect.com/science/article/pii/S0892036214001809
4. Christakis D, Rivara F. JAMA Pediatrics editors’ summary podcast: Association Between Maternal Fluoride Exposure During Pregnancy and IQ Scores in Offspring in Canada [Internet]. JAMA Pediatrics. 2019 [cited 2022 Mar 14]. Available from: https://edhub.ama-assn.org/jn-learning/audio-player/17802991
5. Cui Y, Yu J, Zhang B, Guo B, Gao T, Liu H. The relationships between thyroid-stimulating hormone and/or dopamine levels in peripheral blood and IQ in children with different urinary iodine concentrations. Neurosci Lett [Internet]. 2020;729(April). Available from: https://doi.org/10.1016/j.neulet.2020.134981
6. Curiel JA, Sanders AE, Christian TML, Lafferty-Hess S, Carsey TM, Lampiris LN, et al. Fluoridation advocacy in referenda where media coverage is balanced yet biased. J Am Dent Assoc [Internet]. 2018;149(4):273-280.e3. Available from: https://doi.org/10.1016/j.adaj.2017.10.016
7. Curiel JA, Slade GD, Christian TML, Lafferty-Hess S, Carsey TM, Sanders AE. Referendum opposition to fluoridation and health literacy: A cross-sectional analysis conducted in three large US cities. BMJ Open [Internet]. 2019;9(2):1–8. Available from: https://doi.org/10.1136/bmjopen-2018-022580 – free text at https://europepmc.org/article/MED/29454461#free-full-text
8. Curzon MEJ, Crocker DC. Relationships of trace elements in human tooth enamel to dental caries. Arch Oral Biol [Internet]. 1978;23(8):647–53. Available from: https://doi.org/10.1016/0003-9969(78)90189-9
9. Dogan MS. Relation of Trace Elements on Dental Health. In: Saleh H, El-Adham E, editors. Trace Elements – Human Health and Environment [Internet]. IntechOpen; 2018. p. 71–83. Available from: http://dx.doi.org/10.5772/intechopen study at https://www.intechopen.com/chapters/60356
10. Farmus L, Till C, Green R, Hornung R, Martinez Mier EA, Ayotte P, et al. Critical windows of fluoride neurotoxicity in Canadian children. Environ Res [Internet]. 2021; Available from: https://doi.org/10.1016/j.envres.2021.111315
11. Green R, Lanphear B, Hornung R, Flora D, Martinez-Mier EA, Neufeld R, et al. Association between Maternal Fluoride Exposure during Pregnancy and IQ Scores in Offspring in Canada. JAMA Pediatr [Internet]. 2019;173(10):940–8. Available from: https://doi.org/10.1001/jamapediatrics.2019.1729
12. Grosse SD, Matte TD, Schwartz J, Jackson RJ. Economic gains resulting from the reduction in children’s exposure to lead in the United States. Environ Health Perspect [Internet]. 2002;110(6):563–9. Available from: https://doi.org/10.1289/ehp.02110563
13. Lippert F, Hara AT. Strontium and caries: A long and complicated relationship. Caries Res [Internet]. 2013;47(1):34–49. Available from: https://doi.org/10.1159/000343008
14. NASEM. Review of the Revised NTP Monograph on the Systematic Review of Fluoride Exposure and Neurodevelopmental and Cognitive Health Effects: A Letter Report (2021) [Internet]. Review of the Revised NTP Monograph on the Systematic Review of Fluoride Exposure and Neurodevelopmental and Cognitive Health Effects: A Letter Report (2021). 2021. Available from: http://nap.edu/26030
15. National Toxicology Program (NTP), Taylor K, Rooney A, Bucher J. Revised NTP Draft Monograph on the: Systematic Review of Fluoride Exposure and Neurodevelopmental and Cognitive Health Effects [Internet]. Vol. revised dr, National Toxicology Program (NTP). 2020. Available from: https://www.nationalacademies.org/event/10-19-2020/docs/D367E7974310921F0DB6706C9288048486419AAD365D
16. Neurath C. Submission to the NAS and NTP: Dose-Response assessment of fluoride neurotoxicity studies [Internet]. 2020. Available from: https://fluoridealert.org/wp-content/uploads/neurath-2020.fan-dose-response-assessment-of-ntp-studies-with-corrections.pdf
17. Neurath C, Connett P, Connett M, Hirzy B. Fluoride Developmental Neurotoxicity: Dose-Response Analyses of Recent High Quality Studies. In: ISEE (International Society for Environmental Epidemiology) 2020 Conference [Internet]. 2020. Available from: https://fluoridealert.org/wp-content/uploads/neurath-2020-isee-eposter-ver11.pdf
18. NRC (National Research Council) Committee on Fluoride in Drinking Water. Fluoride in Drinking water: A scientific review of EPA’s standards [Internet]. Washington DC; 2006. Available from: https://www.nap.edu/catalog/11571/fluoride-in-drinking-water-a-scientific-review-of-epas-standards
19. Pathak MU, Shetty V, Kalra D. Trace Elements and Oral Health: A Systematic Review. J Adv Oral Res [Internet]. 2016;7(2):12–20. Available from: https://journals.sagepub.com/doi/pdf/10.1177/2229411220160203
20. Qamar Z, Rahim ZBHA, Chew HP, Fatima T. Influence of trace elements on dental enamel properties: A review. J Pak Med Assoc [Internet]. 2017;67(1):116–20. Available from: https://jpma.org.pk/article-details/8056?article_id=8056
21. Riddell JK, Malin A, Flora D, McCague H, Till C. Association of water fluoride and urinary fluoride concentrations with Attention Deficit Hyperactivity Disorder in Canadian Youth. Environ Int [Internet]. 2019;133(May):105190. Available from: https://doi.org/10.1016/j.envint.2019.105190
22. Till C, Green R, Flora D, Hornung R, Martinez-Mier EA, Blazer M, et al. Fluoride exposure from infant formula and child IQ in a Canadian birth cohort. Environ Int [Internet]. 2020;134(July 2019):4–11. Available from: https://doi.org/10.1016/j.envint.2019.105315
23. Valdez Jiménez L, Guzmán ODL, Flores MC, Costilla-Salazar R, Hernández JC, Contreras YA, et al. In utero exposure to fluoride and cognitive development delay in infants. Neurotoxicology [Internet]. 2017;59:65–70. Available from: https://doi.org/10.1016/j.neuro.2016.12.011
24. Wang M, Liu L, Li H, Li Y, Liu H, Hou C, et al. Thyroid function, intelligence, and low-moderate fluoride exposure among Chinese school-age children. Environ Int [Internet]. 2020;134(January 2019). Available from: https://doi.org/10.1016/j.envint.2019.105229
25. World Medical Association. WMA Declaration of Helsinki – Ethical Principles for Medical Research Involving Human Subjects [Internet]. 2013. Available from: https://www.wma.net/policies-post/wma-declaration-of-helsinki-ethical-principles-for-medical-research-involving-human-subjects/
26. Yu X, Xia L, Zhang S, Zhou G, Li Y, Liu H, et al. Fluoride exposure and children’s intelligence: Gene-environment interaction based on SNP-set, gene and pathway analysis, using a case-control design based on a cross-sectional study. Environ Int [Internet]. 2021;155. Available from: https://doi.org/10.1016/j.envint.2021.106681
27. Zhang S, Zhang X, Liu H, Qu W, Guan Z, Zeng Q, et al. Modifying Effect of COMT Gene Polymorphism and a Predictive Role for Proteomics Analysis in Children’s Intelligence in Endemic Fluorosis Area in Tianjin, China. Toxicol Sci [Internet]. 2015;144(2):238–45. Available from: http://www.toxsci.oxfordjournals.org/cgi/doi/10.1093/toxsci/kfu311
28. Zhao L, Yu C, Lv J, Cui Y, Wang Y, Hou C, et al. Fluoride exposure, dopamine relative gene polymorphism and intelligence: A cross-sectional study in China. Ecotoxicol Environ Saf [Internet]. 2021;209(December 2020):111826. Available from: https://doi.org/10.1016/j.ecoenv.2020.111826
29. Zhou G, Zhao Q, Luo C, Liu H, Li P, Cui Y, et al. Low-moderate fluoride exposure and intelligence among Chinese school-aged children: Role of circulating mtDNA content. Sci Total Environ [Internet]. 2021;786:147330. Available from: https://doi.org/10.1016/j.scitotenv.2021.147330
from Slade Deposition, August 13, 2019
From the deposition of Dr. Gary Slade, taken August 13, 2019 for the lawsuit:
IN THE UNITED STATES DISTRICT COURT FOR THE NORTHERN DISTRICT OF CALIFORNIA AT SAN FRANCISCO
FOOD & WATER WATCH, et al. Plaintiffs
U.S. ENVIRONMENTAL PROTECTION AGENCY, et al. Defendants
Civ. No. 17-CV-02162-EMC
– Dr. Slade acknowledges not expert in non-dental effects of fluoride, in neurotoxicity, in risk-benefit analysis, and has never done a study looking at fluoride’s effects from exposure in first year of life
Q Do you consider yourself an expert
on any nondental health effects of fluoride?
A [Dr. Slade:] Well, I am struggling to think of
any. If someone read off a long, long list,
hypothetically there may be something that I
have some expertise in that I’m just not
coming to mind.
Q Well, let me then give you some
examples. Do you consider yourself an expert
on the neurological effects of fluoride?
A I do not have above, you know,
undergraduate training in neurologic disease.
I have had some passing involvement in my
professional career with studies that were
investigating dental amalgam and its potential
effects on cognitive development and IQ.
So I had some passing familiarity
with the field. Again, I am not calling
myself an expert because I am not exactly sure
what that word means.
Q Well, my question was about
fluoride’s neurological effects. Do you
consider yourself an expert on fluoride’s
A So I was answering about
neurological disease and cognitive
development. My experience with it was in
that instance with amalgam. I do not call
myself an expert on neurologic effects of
Q Well, but what you’ve — correct me
if I’m wrong, but what you’ve just told me is
you’ve published studies on the effectiveness
of water fluoridation during childhood and
childhood includes infancy. That’s a broader
umbrella than I’m referring to here.
I am asking if you have any studies
that you’ve ever done which specifically
present data on the effectiveness or lack
thereof of fluoride exposure during the first
year of life.
A So if this will help, I’m trying to
think of instances where I’ve looked at,
say — presented tables of figures for showing
fluoride exposure for this part of life versus
that part of life, you know, maybe through
adolescence and then adulthood, that kind of
thing or that generational example.
I cannot think right now of a table
that would have zero to one being, say, an
exposure window. Now, if you can find one I
will stand corrected, but as we’re speaking
now, I’m struggling to remember anything at
that level that you have just described.
Q So you know this case is dealing
with neurological effects of fluoride, right?
A I believe it’s — that is one of the
factors being considered.
Q Now, I know that you — it’s your
opinion that water fluoridation is safe. So
the questions I’m about to ask you I’m not
asking you to change your opinion on that or
to — I know that you think it’s safe. I’m
going to ask you some hypothetical questions
here; do you understand that?
Q· · But again, just to be clear, under
this hypothetical you are convinced that the
quality of evidence shows that water
fluoridation causes mental retardation.· At
that point you would still need to do a
risk/benefit analysis before you made your
decision; is that correct?
A Well, I would want to see evidence
of competing risks and benefits. So I
wouldn’t necessarily — I would not do those
studies. I mean I’m not a harm/benefit type
– Slade acknowledges lack of blinding can bias studies
– Slade has never done studies of fluoride and caries that used blinding
– No RCT of fluoridated water has ever been done by anyone
Q Are you aware that there have been
meta-reviews published that have looked at and
examined various types of health interventions
to assess the effect of lack of blinding?
A I have general knowledge of that
area. I mean, I teach some of this stuff to
students and I make mention of that. A
meta-analysis I don’t recall having seen
recently. No, I don’t recall having seen a
meta-analysis. Can you give me an example?
Q Well, I’m just asking for your
awareness. So are you aware that some
meta-reviews have been conducted to assess the
effect of lack of blinding, and these
meta-reviews have concluded that the lack of
blinding is associated with an increased
effect size in the ballpark of 25 to
A So you said meta-reviews. They
sound like systematic reviews with
meta-analysis that — and if they were done in
clinical trials, I could imagine that has been
done.· But I have — I am not familiar with
the specific studies. I suspect — so I am
not familiar with the specific study.
Q Does it surprise you to hear that
meta-reviews have found that the lack of
blinding is associated with an increased
effect size in the ballpark of 25 to 30
A I’d want to read the studies. If
we’re talking about studies of treatments, you
know, typical randomized control trials of
therapy, you know, I — the typical
expectation is that the source of bias
inflates effect estimates.
A Now, if someone’s done a — you said
meta-review. If someone’s done a
meta-analysis to quantify it, I’d be very
interested to read it from my general teaching
Q How many of the epidemiological
studies of fluoridation and caries have used a
A So now we’re talking about blinding
of examiners, let’s say, to the exposure
status of the kids. Oh, not many.
Q· · Have any of your studies involved
A· · Boy.
Q· · Any of your epidemiological studies
of fluoridation and caries, have any of them
used blinded examiners?
A· · So my studies, I haven’t taken
specific steps to blind examiners in my
Q· · Okay.· Now, how many — can you —
how many studies are you aware of,
epidemiological studies of fluoridation and
caries, that have used blinded examiners?
A· · There’s one, was it in Scotland, a
little island or somewhere up North Country,
and I believe also — and certainly done it
for radiographic-type assessments, and that’s
why I’m hesitating to say that none of my
Marnie, I don’t — he probably
doesn’t use radiographs, but Hopcraft did, I
reckon, and I think that was blinded.· But I’m
not a coauthor on that study.
So there has been a few.· I’d
hesitate to put a number on it.
Q· · Fair to say that you could count on
one hand the number of studies on fluoridation
and caries that have used blinded examiners?
A· · The studies that I know of that I
can think of right now, that sort of number is
what comes to mind.
Q· · Now, those early intervention
studies by Arnold and Dean, none of those were
A· · Look, the vast majority were not.
If there was an exception, I don’t remember
it.· So I would say they’re not blinded.
Q· · And none of those early studies by
Dean, Arnold and others were — used a
randomized procedure, correct?
A· · Well, to randomly allocate, you
mean, which is —
Q· · Right.
A· · No, they didn’t.· There would be no
randomized control trial of, say, fluoride in
Q· · Okay.· So let me — I don’t think I
asked you that.· There has been — there has
never been an RCT of water fluoridation,
A· · No randomized control trial of water
fluoridation’s effect on dental caries, no.
– Dr. Slade paid to defend fluoridation in federal lawsuit
Q· · So when were you first asked to
serve as an expert in this litigation?
A· · A little over a year ago.· The exact
date, maybe in the first half of last year.
Q· · So some point maybe in the summer
A· · Maybe even a bit earlier.
Q· · And so your estimated costs at that
time in, what, November of 2018 was a total of
$22,400 for your work in this case?
A· · Yes, that’s what it’s estimated at
on this back side, yes.
Q· · Now, besides counsel — and your
hourly rate in this case is $100, correct?
A· · Correct, $100 an hour.
– Dr. Slade an advocate for expanding water fluoridation
Q· · Okay.· Now Dr. Slade, you are an
advocate of water fluoridation, correct?
A· · So I have published papers
describing my interpretation of results to
show that fluoridation is effective in
preventing dental caries as a public health
dentist.· Advocacy is part of public health
practice so I advocate for dental health in
general and children’s dental health and
prevention.· So I advocate for fluoridation as
a — and fluorides — as a part of that.
· · · · · So that is the extent of my
Q· · You’re also on the Scientific
Advisory Board of the American Fluoridation
A· · Yes.
Q· · And the American Fluoridation
Society is an organization that is dedicated
to promoting water fluoridation, correct?
A· · That’s correct.
Q· · Do you feel in any way uncomfortable
saying that you want to do what you can to
promote the expansion of fluoridated water
throughout this country?
A· · Uncomfortable.· I do advocate for
expansion of fluoridation.· My comfort — I am
just struggling to understand the comfort part
of that question.