Biomarkers for the Assessment of Exposure to Fluoride in Adults

Abstract

To monitor deficient or excessive intakes of biologically available fluoride (F), various biological samples have been tested for use as biomarkers of human exposure to F. Most such studies have concerned children and often have only involved measurement of F in 1 or 2 types of sample. The present study investigated the relationships of F concentrations in biomarkers of F exposure; including plasma, saliva, hair, finger- and toenails, and daily urinary F excretion (UFE) with the total daily F intake (TDFI) of adults. TDFI was assessed in 60 healthy adults, aged ≥20 years; 31 lived in a low-F water area (LFA, 0.04 mg F/L) and 29 in a high-F water area (HFA, 3.05 mg F/L) of Nigeria. All volunteers provided at least 1 biomarker sample from the above list and completed a questionnaire to evaluate F intake from the diet and toothpaste ingestion. TDFI, UFE and F concentrations of biomarkers were statistically significantly higher in the HFA than in the LFA. There were strong statistically significant positive correlations between TDFI and UFE (<i>ρ</i> = 0.730, <i>p</i> < 0.001); plasma F (<i>ρ</i> = 0.729, <i>p</i> < 0.001); fasting whole saliva F (<i>ρ</i> = 0.653, <i>p</i> < 0.001) and hair F (<i>ρ</i> = 0.603, <i>p</i> < 0.001). The statistically significant positive correlations between TDFI and fingernail F (<i>ρ</i> = 0.502, <i>p</i> < 0.001) and between TDFI and toenail F (<i>ρ</i> = 0.556, <i>p</i> < 0.001) were moderate. In conclusion, this study has indicated the usefulness of 24-h UFE as well as F concentration in plasma, fasting whole saliva and hair as biomarkers of contemporary or sub-chronic F exposure in groups of adults. However, they do not appear to have the necessary sensitivity to predict F exposure in individuals.

Fluoride Intake Through Dental Care Products: A Systematic Review

“…In this study, the authors actually reported that some subjects brushed their teeth three or four times a day. Another study also showed a non-negligible contribution of toothpaste to the TDFI, with an F ingestion from toothpaste of ∼12 and 3% for 31 and 29 adults in poor and high-fluoridated areas, respectively [47].…”

“…The 28 selected articles can be mentioned more than once depending on their categories of fluoridated tap water (explained in methods). Only two studies were performed with adults whose ages ranged from 20 to 35 years [28,47]. Some studies present a high number of participants, however, in some of these publications, the number of children using dental care products can narrow down to 5% of the initial cohort [36].…”

“…Extremely high F concentrations in the water (>1.5 mg/L) were associated with a lower contribution of toothpaste, <20% of the total F intake. Among the three measurements included in our database, one was measured on an adult population supposed to have a better use of toothpaste (no swallowing) [47]. Therefore, between the two studies carried out in extremely high-fluoridated areas in children (>1.5 mg/L), only one reported an extremely high daily dietary input (Figure 2C) [36,46].…”

“…In adults, the mean contribution of dental care products to the total exposure was 12% in poor, 95% in low, 53% in medium, and 3% in extremely-fluoridated water (Table 3) [28,47].…”

“…Due to their better practice, adults should not be exposed to F through dental care products (Supplementary Figure 2) [28,47]. However, Cardoso et al (2006) reported high percentage values of toothpaste contribution that varied between 26 and 95% (Supplementary Figure 2) [28].…”