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Taher MK, Momoli F, Go J, Hagiwara S, Ramoju S, Hu X, Jensen N, Terrell R, Hemmerich A, Krewski D. Systematic review of epidemiological and toxicological evidence on health effects of fluoride in drinking water. Crit Rev Toxicol 2024; 54:2-34. [PMID: 38318766 DOI: 10.1080/10408444.2023.2295338] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2023] [Accepted: 11/27/2023] [Indexed: 02/07/2024]
Abstract
INTRODUCTION Fluoride is a naturally occurring substance that is also added to drinking water, dental hygiene products, and food supplements for preventing dental caries. Concerns have been raised about several other potential health risks of fluoride. OBJECTIVE To conduct a robust synthesis of evidence regarding human health risks due to exposure to fluoride in drinking water, and to develop a point of departure (POD) for setting a health-based value (HBV) for fluoride in drinking water. METHODS A systematic review of evidence published since recent reviews of human, animal, and in vitro data was carried out. Bradford Hill considerations were used to weigh the evidence for causality. Several key studies were considered for deriving PODs. RESULTS The current review identified 89 human studies, 199 animal studies, and 10 major in vitro reviews. The weight of evidence on 39 health endpoints was presented. In addition to dental fluorosis, evidence was considered strong for reduction in IQ scores in children, moderate for thyroid dysfunction, weak for kidney dysfunction, and limited for sex hormone disruptions. CONCLUSION The current review identified moderate dental fluorosis and reduction in IQ scores in children as the most relevant endpoints for establishing an HBV for fluoride in drinking water. PODs were derived for these two endpoints, although there is still some uncertainty in the causal weight of evidence for causality for reducing IQ scores in children and considerable uncertainty in the derivation of its POD. Given our evaluation of the overall weight of evidence, moderate dental fluorosis is suggested as the key endpoint until more evidence is accumulated on possible reduction of IQ scores effects. A POD of 1.56 mg fluoride/L for moderate dental fluorosis may be preferred as a starting point for setting an HBV for fluoride in drinking water to protect against moderate and severe dental fluorosis. Although outside the scope of the current review, precautionary concerns for potential neurodevelopmental cognitive effects may warrant special consideration in the derivation of the HBV for fluoride in drinking water.
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Affiliation(s)
- Mohamed Kadry Taher
- McLaughlin Centre for Population Health Risk Assessment, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada
- School of Epidemiology and Public Health, University of Ottawa, Ottawa, ON, Canada
- School of Mathematics and Statistics, Carleton University, Ottawa, ON, Canada
| | - Franco Momoli
- School of Epidemiology and Public Health, University of Ottawa, Ottawa, ON, Canada
- Risk Sciences International, Ottawa, ON, Canada
| | - Jennifer Go
- School of Epidemiology and Public Health, University of Ottawa, Ottawa, ON, Canada
- Risk Sciences International, Ottawa, ON, Canada
| | - Shintaro Hagiwara
- School of Mathematics and Statistics, Carleton University, Ottawa, ON, Canada
- Risk Sciences International, Ottawa, ON, Canada
| | - Siva Ramoju
- Risk Sciences International, Ottawa, ON, Canada
| | - Xuefeng Hu
- Department of Biology, Faculty of Science, University of Ottawa, Ottawa, ON, Canada
| | - Natalie Jensen
- School of Epidemiology and Public Health, University of Ottawa, Ottawa, ON, Canada
- Risk Sciences International, Ottawa, ON, Canada
| | - Rowan Terrell
- School of Epidemiology and Public Health, University of Ottawa, Ottawa, ON, Canada
- Risk Sciences International, Ottawa, ON, Canada
| | - Alex Hemmerich
- Risk Sciences International, Ottawa, ON, Canada
- Faculty of Education, Queen's University, Kingston, ON, Canada
| | - Daniel Krewski
- McLaughlin Centre for Population Health Risk Assessment, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada
- School of Epidemiology and Public Health, University of Ottawa, Ottawa, ON, Canada
- School of Mathematics and Statistics, Carleton University, Ottawa, ON, Canada
- Risk Sciences International, Ottawa, ON, Canada
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