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Abstract

Background

Previous studies have shown a correlation between fluoride concentrations in urine and community water fluoride concentrations. However, there are no studies of the relationship between community water fluoridation, urine, serum, and amniotic fluid fluoride concentrations in pregnant women in the US. The aim of this study was to determine the relationship between maternal urine fluoride (MUF), maternal urine fluoride adjusted for specific gravity (MUFSG), maternal serum fluoride (MSF), amniotic fluid fluoride (AFF) concentrations during pregnancy, and community water fluoridation in Northern California.

Methods

Archived samples of urine, serum and amniotic fluid collected from second trimester pregnant women in Northern California from 47 different communities in Northern California and one from Montana (n = 48), were analyzed for fluoride using an ion specific electrode following acid microdiffusion. Women’s addresses were matched to publicly reported water fluoride concentrations. We examined whether fluoride concentrations in biospecimens differed by fluoridation status of the community water, and determined the association between water fluoride concentrations and biospecimen fluoride concentrations using linear regression models adjusted for maternal age, smoking, Body Mass Index (BMI), race/ethnicity, and gestational age at sample collection.

Results

Fluoride concentrations in the community water supplies ranged from 0.02 to 1.00 mg/L. MUF, MSF , and AFF concentrations were significantly higher in pregnant women living in communities adhering to the U.S. recommended water fluoride concentration (0.7 mg/L), as compared with communities with less than 0.7 mg/L fluoride in drinking water. When adjusted for maternal age, smoking status, BMI, race/ethnicity, and gestational age at sample collection, a 0.1 mg/L increase in community water fluoride concentration was positively associated with higher concentrations of MUF (B = 0.052, 95% CI:0.019,0.085), MUFSG (B = 0.028, 95% CI: -0.006, 0.062), MSF (B = 0.001, 95% CI: 0.000, 0.003) and AFF (B = 0.001, 95% CI: 0.000, 0.002).

Conclusions

We found universal exposure to fluoride in pregnant women and to the fetus via the amniotic fluid. Fluoride concentrations in urine, serum, and amniotic fluid from women were positively correlated to public records of community water fluoridation. Community water fluoridation remains a major source of fluoride exposure for pregnant women living in Northern California.

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Excerpt:

Introduction

In the United States (US), water and water-based beverages contribute to approximately 75% of the total fluoride intake among adults living in communities that fluoridate their water supply [1]. The most recent estimates posted by the US Centers for Disease Control and Prevention (CDC), are that nearly three-fourths of the U.S. population with access to community water systems receive water adjusted to the federally recommended concentration of 0.7 mg/L fluoride (https://www.cdc.gov/fluoridation/statistics/2016stats.htm). This concentration of community water fluoridation in the US is higher than in Canada, where approximately one-third of Canadian communities fluoridate their water supply, and Europe, where only 3% of Europeans have fluoridated water [2, 3]. Recent studies of the potential effects of fluoride on neurodevelopment from prenatal exposures [4,5,6,7,8], and the onset of puberty in boys [6], suggest the need to evaluate fluoride concentrations in communities in the US and their relationship to fluoride concentrations in pregnant women.

Enamel fluorosis, which is a bioindicator for systemic fluoride exposure during times of tooth enamel formation, has been increasing in the US. In 1986–1987, 22.6% of adolescents aged 12–15 were reported to have dental fluorosis, and this increased to 40.7% in 1999–2004 [9]. In adolescents aged 16 and 17 years, fluorosis prevalence was reported to have again increased by 31.6% in 2012–2011, as compared with concentrations in 2002–2001 [10]. The purported increase in enamel fluorosis has led to concerns that overall systemic fluoride exposure is increasing, and in 2015 the CDC recommended concentrations for fluoride in drinking water be reduced from 1 mg/L fluoride to 0.7 mg/L fluoride [11]. However, the US Environmental Protection Agency has continued to allow fluoride concentrations of up to 4 mg/L in drinking water (https://www.epa.gov/ground-water-and-drinking-water/national-primary-drinking-water-regulations).

There are no contemporary measurements of systemic fluoride in adult humans in the United States, and no evaluation of their relationship to water fluoridation. Additionally, there are no contemporary studies of fluoride concentrations in pregnant women in fluoridated communities in the US, nor in fetal related tissues, despite recent concerns about effects on neurodevelopment.

To address this, we measured fluoride concentrations in urine, serum and amniotic fluid of second trimester pregnant women in Northern California. We used publicly available information on fluoride concentrations in their water systems to evaluate the relationship between reported fluoride concentrations and biomonitoring measurements, to assess the contribution of water fluoridation to measured fluoride concentrations in biological samples.

… Fig. 1

figure1

Map of the location of pregnant women participants and the community water fluoridation concentrations. Note: One participant lived in Montana at the time of sample collection but was excluded from this map for clarity

Full size image

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Acknowledgements

Not applicable.

Funding

This work was supported by NIH P01ES022841, US EPA RD 83543301, and the Center for Children’s Oral Health Research (UCSF).

 

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