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J Epidemiol Community Health. 2017 Oct;71(10):1019-1025. doi: 10.1136/jech-2017-209129. Epub 2017 Aug 24.

Fluoride exposure and indicators of thyroid functioning in the Canadian population: implications for community water fluoridation.

Author information

1
Department of Cancer Epidemiology and Prevention Research, Alberta Health Services, Calgary, Alberta, Canada.
2
Department of Community Health Sciences and O'Brien Institute for Public Health, University of Calgary, Calgary, Alberta, Canada.
3
Faculty of Medicine, University of Queensland, Herston, Queensland, Australia.
4
Dental Public Health, Faculty of Dentistry, University of Toronto, Toronto, Ontario, Canada.

Abstract

BACKGROUND:

There are concerns that altered thyroid functioning could be the result of ingesting too much fluoride. Community water fluoridation (CWF) is an important source of fluoride exposure. Our objectives were to examine the association between fluoride exposure and (1) diagnosis of a thyroid condition and (2) indicators of thyroid functioning among a national population-based sample of Canadians.

METHODS:

We analysed data from Cycles 2 and 3 of the Canadian Health Measures Survey (CHMS). Logistic regression was used to assess associations between fluoride from urine and tap water samples and the diagnosis of a thyroid condition. Multinomial logistic regression was used to examine the relationship between fluoride exposure and thyroid-stimulating hormone (TSH) level (low/normal/high). Other available variables permitted additional exploratory analyses among the subset of participants for whom we could discern some fluoride exposure from drinking water and/or dental products.

RESULTS:

There was no evidence of a relationship between fluoride exposure (from urine and tap water) and the diagnosis of a thyroid condition. There was no statistically significant association between fluoride exposure and abnormal (low or high) TSH levels relative to normal TSH levels. Rerunning the models with the sample constrained to the subset of participants for whom we could discern some source(s) of fluoride exposure from drinking water and/or dental products revealed no significant associations.

CONCLUSION:

These analyses suggest that, at the population level, fluoride exposure is not associated with impaired thyroid functioning in a time and place where multiple sources of fluoride exposure, including CWF, exist.

KEYWORDS:

drinking; fluoride; surveys and questionnaires; thyroid gland; water

PMID:
28839078
PMCID:
PMC5754860
DOI:
10.1136/jech-2017-209129
[Indexed for MEDLINE]
Free PMC Article

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