84. Associations between Urinary, Dietary, and Water Fluoride Concentrations among Children in Mexico and Canada (lay summary)

Green R, Till C, Cantoral A, Lanphear BP, Martinez-Mier EA, Ayotte P, Wright RO, Tellez-Rojo MM, Malin AJ. Toxics. 2020 Nov 20;8(4):E110. doi: 10.3390/toxics8040110

Fluoride is a mineral found naturally in most water sources. About one-third of Canadians have fluoride added to their public water supply to protect teeth from decay. In Mexico City, fluoride is added to salt to prevent dental caries. While fluoride at low concentrations can improve oral health, concerns have been raised about the health effects of fluoride exposure particularly in young children.  It is, therefore, important to understand the levels and sources of fluoride exposure in children.

The purpose of this study was to measure and compare childhood urinary fluoride concentrations in children enrolled in two studies – the MIREC study in Canada and the PROGRESS study in Mexico City.  The researchers also wanted to investigate how drinking water and dietary levels of fluoride contribute to childhood urinary concentrations.  In the MIREC study, researchers compared fluoride concentrations in municipal drinking water to urinary fluoride concentrations.  In the PROGRESS study, the contribution of dietary sources to urinary fluoride concentrations was estimated based on self-reported intake of food and beverage over the previous week and measurement of fluoride in foods.

The study included 561 children from the PROGRESS study and 645 children from the MIREC study.  The age of the children in the MIREC study ranged from 2 to 6 whereas those in the Mexican study ranged from 4-6.  The researchers found that the average concentrations in the Mexican study were comparable to those found in the Canadian cities with fluoridated water.  For example, average urinary fluoride concentrations in MIREC children ages 4-6 who lived in regions with fluoridated water was 0.79 mg/L whereas the average urinary fluoride concentrations among PROGRESS children of the same age was 0.74 mg/L.  Urinary fluoride concentrations in MIREC children who lived in regions without fluoridated water were, on average, 0.42 mg/L. Drinking water sources of fluoride correlated well with the urinary fluoride concentrations but dietary sources did not.

In conclusion, despite differences in sources of exposure, Canadian children who live in fluoridated communities had comparable urinary fluoride concentrations to children from Mexico City.  The researchers demonstrate that fluoridation of municipal drinking water is a source of exposure for Canadian children.  It will be interesting to continue to explore how fluoride concentrations might change as children get older and further understand the potential health effects of fluoride exposure in early childhood.