55. Community Water Fluoridation and Urinary Fluoride Concentrations in a National Sample of Pregnant Women in Canada (lay summary)

Till C, Green R, Grundy JG, Hornung R, Neufeld R, Martinez-Mier EA, Ayotte P, Muckle G, Lanphear BP. Environmental Health Perspectives. 2018 Oct 10;126(10). doi.org/10.1289/EHP3546

Fluoride is a mineral that can be found naturally in water, food and soil. A number of cities in Canada adjust fluoride levels in drinking water to help prevent dental cavities. Other sources of fluoride include beverages (e.g., tea, coffee and juices), dental products (e.g., toothpastes, mouth rinses), and other consumer products such as supplements. In adults, approximately 50-75% of the fluoride consumed appears in the urine within 24 hours after ingestion. So far, no studies in North America have compared fluoride levels in urine of pregnant women with the fluoride concentrations in the drinking water of the cities where they live. The objective of this study was to identify factors that were associated with urinary fluoride levels in pregnant women.

In this MIREC Biobank project, researchers measured fluoride concentrations in urine during each trimester of pregnancy from 1,566 women living in 10 cities across Canada. Adjustments were made for urinary dilution. Information on the woman’s education, family income, country of birth and tea consumption habits was collected in the questionnaires. The first 3 characters of the woman’s postal code were used to locate which water treatment plant(s) serviced her home. Fluoride concentrations in city drinking water during the time period of the pregnancy were obtained from the cities. Toronto, Hamilton, Ottawa, Sudbury, Halifax, Edmonton, and Winnipeg add fluoride to their drinking water while Vancouver, Montreal, and Kingston do not.

This study showed that average fluoride concentrations in maternal urine were almost two times higher among women living in fluoridated than non-fluoridated communities. Drinking black tea but not green tea was also associated with higher levels of fluoride in maternal urine.

In conclusion, this study found that community water fluoridation is a major source of fluoride exposure for pregnant women living in Canada.

This MIREC Biobank study was led by researchers at York University in Toronto.