Hi all…a study measuring urinary fluoride levels in pregnant women in Canada has just appeared in the journal Environmental Health Perspectives. The authors conclude that “community water fluoridation is a major source of fluoride exposure for pregnant women living in Canada.” They also conclude that “Given the widespread exposure to fluoride and recent findings (Bashash et al. 2017) showing reductions in child IQ with gestational exposure to fluoride, the present study is an important step in quantifying fluoride exposure, patterns of exposure, and major sources of fluoride exposure in pregnant women. Research is urgently needed to determine whether prenatal exposure to fluoride contributes to neurodevelopmental outcomes in the offspring of these women.”

They also report that their “ability to compare the urinary fluoride data with an external source of fluoride (public drinking water) is an important strength of the study. It is notable that minimum and maximum concentrations of fluoride in public drinking-water supplies differed substantially across cities and from year to year (see Table S3).” However, I was unable to download this table at this time.

These findings may attract the attention of media or groups opposed to fluoridation so it might be useful to be aware of its existence, especially in communities where fluoridation is practiced or is an issue. It is important to note the limitations of the study, some of which are summarized on the last couple of pages. As an FYI, it is mentioned that the biological half life of fluoride in humans is about 6 hours. The article is open access.

Bill

Community Water Fluoridation and Urinary Fluoride Concentrations in a National Sample of Pregnant Women in Canada

Christine Till, Rivka Green, John G. Grundy, Richard Hornung, Raichel Neufeld, E. Angeles Martinez-Mier, Pierre Ayotte, Gina Muckle, and Bruce Lanphear
Environmental Health Perspectives Vol. 126, No. 10  October 2018
https://ehp.niehs.nih.gov/doi/pdf/10.1289/EHP3546

Background:

Fluoride exposures have not been established for pregnant women who live in regions with and without community water fluoridation.

Objective:

Our aim was to measure urinary fluoride levels during pregnancy. We also assessed the contribution of drinking-water and tea consumption habits to maternal urinary fluoride (MUF) concentrations and evaluated the impact of various dilution correction standards, including adjustment for urinary creatinine and specific gravity (SG).

Methods:

We measured MUF concentrations in spot samples collected in each trimester of pregnancy from 1,566 pregnant women in the Maternal–Infant Research on Environmental Chemicals cohort. We calculated intraclass correlation coefficients (ICCs) to assess variability in MUF concentrations across pregnancy. We used regression analyses to estimate associations between MUF levels, tea consumption, and water fluoride concentrations as measured by water treatment plants.

Results:

Creatinine-adjusted MUF values (mean±SD mean±SD; milligrams per liter) were almost two times higher for pregnant women living in fluoridated regions (0.87±0.50) compared with nonfluoridated regions (0.46±0.34; p<0.001). MUF values tended to increase over the course of pregnancy using both unadjusted values and adjusted values. Reproducibility of the unadjusted and adjusted MUF values was modest (ICC range=0.37–0.40). The municipal water fluoride level was positively associated with creatinine-adjusted MUF (B=0.52, 95% CI: 0.46, 0.57), accounting for 24% of the variance after controlling for covariates. Higher MUF concentrations correlated with numbers of cups of black (r=0.31–0.32 but not green tea (r=0.04–0.06). Urinary creatinine and SG correction methods were highly correlated (r=0.91) and were interchangeable in models examining predictors of MUF.

Conclusion:

Community water fluoridation is a major source of fluoride exposure for pregnant women living in Canada. Urinary dilution correction with creatinine and SG were shown to be interchangeable for our sample of pregnant women.” https://doi.org/10.1289/EHP3546