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

Abstract

BackgroundThere 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.MethodsWe 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.ResultsThere 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.ConclusionThese 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.

Fluoride ingestion and thyroid function in children resident of naturally fluoridated areas - An observational study

“…In accordance to our study results Baum K 1981 (16) and Barberio et al , 2017 (17) reported fluoride exposure do not increase susceptibility to impaired thyroid functioning at the population-level. Our results are also in accordance with the endorsed statement quote by the British Thyroid association in 2006 and European Union’s 2011 SCHER report on health and environmental risks of fluoride, that human studies do not suggest an association between water fluoridation and any thyroid disorder.…”

Fluoride exposure and indicators of thyroid functioning: study design and data analysis considerations

“…For example, among individuals with primary hypothyroidism, UF levels were found to range from 0.22 to 0.98 mg/L. The range reported in the controls was 0.49 to 0.61 mg/L 1. What these data show is that among patients with primary hypothyroidism, a subgroup of patients had very low UF levels with another subgroup demonstrating elevated UF above the normal range.…”

“…Barberio et al 1 reported that there was no evidence of a relationship between fluoride exposure and the diagnosis of a thyroid condition among a subsample of respondents available from Statistics Canada’s Canadian Health Measures Survey. On review, however, their data show that the mean urinary fluoride (UF) level in patients with primary hypothyroidism was 0.60 mg/L compared with 0.55 mg/L for individuals without this condition.…”

Analysis of the protective effects of γ-aminobutyric acid during fluoride-induced hypothyroidism in male Kunming mice

“…The thyroid is sensitive to EEDs, particularly fluoride (Barberio et al. 2017). Fluorine is widely distributed in nature and is absorbed by the human body through food, water, and air.…”