Journal Article

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

Hosein, F Shaun, Barberio, Amanda M, McLaren, Lindsay, Quiñonez, Carlos

2017

Overview

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.

• Publisher: BMJ Publishing Group Ltd,BMJ Publishing Group LTD,BMJ Publishing Group
• Subject: Adolescent / Adult / Autoimmune diseases / Biomarkers / Canada - epidemiology / Data processing / Drinking water / Drinking Water - analysis / Drinking Water - chemistry / Environmental Exposure - adverse effects / Exposure / Female / Fluoridation / Fluoridation - adverse effects / Fluorides / Fluorides - adverse effects / Health Surveys / Hormones / Humans / Hypothyroidism / Hypothyroidism - chemically induced / Hypothyroidism - epidemiology / Iodine / Laboratory animals / Logistic Models / Male / Middle Aged / Nutrition research / Population Surveillance / Procedure manuals / Public health / Research Report / Statistical analysis / Supplies / Thyroid / Thyroid diseases / Thyroid Function Tests / Thyroid Gland - metabolism / Thyroid Gland - physiology / Thyroid Gland - physiopathology / Thyroid-stimulating hormone / Thyrotropin - blood / Urine / Water analysis / Water sampling / Water Supply / Young Adult