Category Archives: Fluoridation

Fluoride exposure in early life as the possible root cause of disease later in life

Tetsuo Nakamoto, H Ralph Rawls. Fluoride Exposure in Early Life as the Possible Root Cause of Disease In Later Life, The Journal of clinical pediatric dentistry. 42 (5), 325-330, 2018 doi: 10.17796/1053-4625-42.5.1

Fluoride, one of the most celebrated ingredients for the prevention of dental caries in the 20th century, has also been controversial for its use in dentifrices and other applications. In the current review, we have concentrated primarily on early-life exposure to fluoride and how it may affect the various organs. The most recent controversial aspects of fluoride are related to toxicity of the developing brain and how it may possibly result in the decrease of intelligence quotient (IQ), autism, and calcification of the pineal gland. In addition, it has been reported to have possible effects on bone and thyroid glands. If nutritional stress is applied during a critical period of growth and development, the organ(s) and/or body will never recover once they pass through the critical period. For example, if animals are force-fed during experiments, they will simply get fat but never reach the normal size. Although early-life fluoride exposure causing fluorosis is well reported in the literature, the dental profession considers it primarily as an esthetic rather than a serious systemic problem. In the current review, we wanted to raise the possibility of future disease as a result of early-life exposure to fluoride. It is not currently known how fluoride will become a cause of future disease. Studies of other nutritional factors have shown that the effects of early nutritional stress are a cause of disease in later life.

“…artificial water fluoridation should be reconsidered globally…”

Stephen Peckham, Niyi Awofeso. Water Fluoridation: A Critical Review of the Physiological Effects of Ingested Fluoride as a Public Health Intervention, ScientificWorldJournal, 2014, 293019.

Fluorine is the world’s 13th most abundant element and constitutes 0.08% of the Earth crust. It has the highest electronegativity of all elements. Fluoride is widely distributed in the environment, occurring in the air, soils, rocks, and water. Although fluoride is used industrially in a fluorine compound, the manufacture of ceramics, pesticides, aerosol propellants, refrigerants, glassware, and Teflon cookware, it is a generally unwanted byproduct of aluminium, fertilizer, and iron ore manufacture. The medicinal use of fluorides for the prevention of dental caries began in January 1945 when community water supplies in Grand Rapids, United States, were fluoridated to a level of 1 ppm as a dental caries prevention measure. However, water fluoridation remains a controversial public health measure. This paper reviews the human health effects of fluoride. The authors conclude that available evidence suggests that fluoride has a potential to cause major adverse human health problems, while having only a modest dental caries prevention effect. As part of efforts to reduce hazardous fluoride ingestion, the practice of artificial water fluoridation should be reconsidered globally, while industrial safety measures need to be tightened in order to reduce unethical discharge of fluoride compounds into the environment. Public health approaches for global dental caries reduction that do not involve systemic ingestion of fluoride are urgently needed.

Fluoride exposure inhibits thyroid iodine uptake

Waugh DT. Fluoride Exposure Induces Inhibition of Sodium/Iodide Symporter (NIS) Contributing to Impaired Iodine Absorption and Iodine Deficiency: Molecular Mechanisms of Inhibition and Implications for Public Health. Int J Environ Res Public Health. 2019 Mar 26;16(6). pii: E1086. doi: 10.3390/ijerph16061086.

The sodium iodide symporter (NIS) is the plasma membrane glycoprotein that mediates active iodide transport in the thyroid and other tissues, such as the salivary, gastric mucosa, rectal mucosa, bronchial mucosa, placenta and mammary glands. In the thyroid, NIS mediates the uptake and accumulation of iodine and its activity is crucial for the development of the central nervous system and disease prevention. Since the discovery of NIS in 1996, research has further shown that NIS functionality and iodine transport is dependent on the activity of the sodium potassium activated adenosine 5′-triphosphatase pump (Na+, K+-ATPase). In this article, I review the molecular mechanisms by which F inhibits NIS expression and functionality which in turn contributes to impaired iodide absorption, diminished iodide-concentrating ability and iodine deficiency disorders. I discuss how NIS expression and activity is inhibited by thyroglobulin (Tg), tumour necrosis factor alpha (TNF-α), transforming growth factor beta 1 (TGF-β1), interleukin 6 (IL-6) and Interleukin 1 beta (IL-1β), interferon-γ (IFN-γ), insulin like growth factor 1 (IGF-1) and phosphoinositide 3-kinase (PI3K) and how fluoride upregulates expression and activity of these biomarkers. I further describe the crucial role of prolactin and megalin in regulation of NIS expression and iodine homeostasis and the effect of fluoride in down regulating prolactin and megalin expression. Among many other issues, I discuss the potential conflict between public health policies such as water fluoridation and its contribution to iodine deficiency, neurodevelopmental and pathological disorders. Further studies are warranted to examine these associations.

Are assumptions regarding fluoride exposure invalid?

Moore D, Goodwin M, Pretty IA. Long-term variability in artificially and naturally fluoridated water supplies in England. Community dentistry and oral epidemiology, 2019 Oct 18. doi: 10.1111/cdoe.12502

OBJECTIVES: To understand the potential impact of exposure misclassification on water fluoridation studies in England, this paper aims to describe the long-term variation in water fluoride concentrations in both artificially and naturally fluoridated water supplies.

METHODS: Water fluoridation dose monitoring data were requested from all five English public water suppliers who artificially fluoridate their water, as well as from one water company that supplies naturally fluoridated water. Descriptive statistics were calculated, including annual means, standard deviations, minimum-maximum and absolute and relative frequencies.

RESULTS: Data were made available by two of the five English water companies who supply artificially fluoridated water and one water company that supplies naturally fluoridated water (40 398 individual samples). The data for fluoridated water spanned 18-35 years, whilst the data on naturally fluoridated water spanned 14 years. The artificially fluoridated samples showed wide variation in fluoride dose control, both between different water treatment works and over time. Mean fluoride concentrations in the artificially fluoridated supplies ranged from 0.53 (SD 0.47) to 0.93 (SD 0.22) mg F/L and were within the optimal range of 0.7-1.0 mg F/L in 27.7%-77.8% of samples. The naturally fluoridated supplies had a higher mean fluoride concentration of 1.06 (SD 0.18) and 1.15 (SD 0.16) mg F/L than the artificially fluoridated supplies, with lower variation over time. The naturally fluoridated supplies were above the optimal range in 75.5% and 53% of samples.

CONCLUSIONS: Assumptions that populations living in areas with a water fluoridation scheme have received optimally fluoridated water (0.7-1.0 mg F/L) are invalid. To support future research endeavours, as well as to provide ‘external control’ and facilitation of optimal dosing, it is recommended that a quarterly record of water fluoride concentrations (mean, standard deviation and minimum and maximum) are made available for every water supply in England, in a format that can be mapped against residential postcodes.

Community water fluoridation is a major source of fluoride exposure for pregnant women, Canada

Christine Till, Rivka Green, John G. Grundy, Richard Hornung, Raichel Neufeld, E. Angeles Martinez-Mier, Pierre Ayotte, Gina Buckle, and Bruce Lanphear.
Community Water Fluoridation and Urinary Fluoride Concentrations in a National Sample of Pregnant Women in Canada. Environmental Health Perspectives Vol. 126, No. 10. https://doi.org/10.1289/EHP3546

Background: Fluoride exposures have not been established for pregnant women who live in regions with and without community water fluoridation.
Objective: Our aim was to measure urinary fluoride levels during pregnancy. We also assessed the contribution of drinking-water and tea consumption habits to maternal urinary fluoride (MUF) concentrations and evaluated the impact of various dilution correction standards, including adjustment for urinary creatinine and specific gravity (SG).

Methods: We measured MUF concentrations in spot samples collected in each trimester of pregnancy from 1,566 pregnant women in the Maternal–Infant Research on Environmental Chemicals cohort. We calculated intraclass correlation coefficients (ICCs) to assess variability in MUF concentrations across pregnancy. We used regression analyses to estimate associations between MUF levels, tea consumption, and water fluoride concentrations as measured by water treatment plants.

Results: Creatinine-adjusted MUF values (mean±SD; milligrams per liter) were almost two times higher for pregnant women living in fluoridated regions (0.87± 0.50) compared with nonfluoridated regions (0.46±0.34; p<0.001). MUF values tended to increase over the course of pregnancy using both unadjusted values and adjusted values. Reproducibility of the unadjusted and adjusted MUF values was modest (ICC range=0.37–0.40). The municipal water fluoride level was positively associated with creatinine-adjusted MUF (B=0.52, 95% CI: 0.46, 0.57), accounting for 24% of the variance after controlling for covariates. Higher MUF concentrations correlated with numbers of cups of black (r=0.31–0.32) but not green tea (r equals 0.04 to 0.06"r=0.91) and were interchangeable in models examining predictors of MUF.

Conclusion: Community water fluoridation is a major source of fluoride exposure for pregnant women living in Canada. Urinary dilution correction with creatinine and SG were shown to be interchangeable for our sample of pregnant women.

Superficial assessment of fluoridation pros and cons

Aoun A, Darwiche F, Al Hayek S, Doumit J. The Fluoride Debate: The Pros and Cons of Fluoridation. Preventive nutrition and food science. 2018 Sep;23(3):171-180. doi: 10.3746/pnf.2018.23.3.171.

Fluoride is one of the most abundant elements found in nature. Water is the major dietary source of fluoride. The only known association with low fluoride intake is the risk of dental caries. Initially, fluoride was considered beneficial when given systemically during tooth development, but later research has shown the importance and the advantages of its topical effects in the prevention or treatment of dental caries and tooth decay. Water fluoridation was once heralded as one of the best public health achievements in the twentieth century. Since this practice is not feasible or cost effective in many regions, especially rural areas, researchers and policy makers have explored other methods of introducing fluoride to the general population such as adding fluoride to milk and table salt. Lately, major concerns about excessive fluoride intake and related toxicity were raised worldwide, leading several countries to ban fluoridation. Health-care professionals and the public need guidance regarding the debate around fluoridation. This paper reviews the different aspects of fluoridation, their effectiveness in dental caries prevention and their risks. It was performed in the PubMed and the Google Scholar databases in January 2018 without limitation as to the publication period.

Fluoride exposure for pregnant women, Canada

Till C, Green R, Grundy JG, Hornung R, Neufeld R, Martinez-Mier EA, Ayotte P, Muckle G, Lanphear B. Community Water Fluoridation and Urinary Fluoride Concentrations in a National Sample of Pregnant Women in Canada. Environmental health perspectives. 2018 Oct;126(10):107001. doi: 10.1289/EHP3546.

BACKGROUND: Fluoride exposures have not been established for pregnant women who live in regions with and without community water fluoridation.

OBJECTIVE: Our aim was to measure urinary fluoride levels during pregnancy. We also assessed the contribution of drinking-water and tea consumption habits to maternal urinary fluoride (MUF) concentrations and evaluated the impact of various dilution correction standards, including adjustment for urinary creatinine and specific gravity (SG).

METHODS: We measured MUF concentrations in spot samples collected in each trimester of pregnancy from 1,566 pregnant women in the Maternal-Infant Research on Environmental Chemicals cohort. We calculated intraclass correlation coefficients (ICCs) to assess variability in MUF concentrations across pregnancy. We used regression analyses to estimate associations between MUF levels, tea consumption, and water fluoride concentrations as measured by water treatment plants.

RESULTS: Creatinine-adjusted MUF values  were almost two times higher for pregnant women living in fluoridated regions  compared with nonfluoridated regions. MUF values tended to increase over the course of pregnancy using both unadjusted values and adjusted values. Reproducibility of the unadjusted and adjusted MUF values was modest . The municipal water fluoride level was positively associated with creatinine-adjusted MUF, accounting for 24% of the variance after controlling for covariates. Higher MUF concentrations correlated with numbers of cups of black but not green tea. Urinary creatinine and SG correction methods were highly correlated and were interchangeable in models examining predictors of MUF.

CONCLUSION: Community water fluoridation is a major source of fluoride exposure for pregnant women living in Canada. Urinary dilution correction with creatinine and SG were shown to be interchangeable for our sample of pregnant women.