Biomarkers for the Assessment of Fluoride Exposure in Children

Abstract

Due to practical difficulties in quantifying fluoride exposure, the ability of various biomarkers to predict it has been investigated previously. However, the results are inadequate for validation of their application and usefulness. This study aimed to investigate the association between contemporary/recent biomarkers of fluoride exposure and total daily fluoride intake (TDFI) of children with large differences in fluoride exposure through drinking water. TDFI was assessed in 61 healthy 4 to 5 years old children who provided at least one biomarker sample; 32 lived in a low-fluoride area (0.04 mgF/L) and 29 lived in a high-fluoride area (3.05 mgF/L). Validated questionnaires were administered to evaluate fluoride intake from diets (including water) and toothpaste ingestion. Daily urinary fluoride excretion (UFE) as well as fluoride concentrations in plasma, fasting whole saliva, hair and nails (toenails/fingernails) were evaluated and related to total fluoride exposure. TDFI, UFE and fluoride concentration of biomarkers were statistically significantly higher in the high-fluoride area than in the low-fluoride area. There was a strong statistically significant positive correlation between TDFI and: UFE (ρ=0.756, p<0.001); plasma fluoride concentration (ρ=0.770, p<0.001); toenail fluoride concentration (ρ=0.604, p<0.001). The statistically significant positive correlation between TDFI and fingernail fluoride concentration (ρ=470, p<0.001) as well as between TDFI and fasting whole saliva fluoride concentration (ρ=0.453, p=0.001) was moderate, whereas it was weak between TDFI and hair fluoride concentration (ρ=0.306, p=0.027). In conclusion, the current study confirmed the suitability of 24h urine samples for estimating F exposure in children. The strong correlations between TDFI and F in plasma and toenails also suggest these biomarkers may be considered for health risk assessments of fluoride in children who are susceptible to development of dental fluorosis. Sample preparation and analysis Urine samples collected over the 24h period were pooled for each participant, and the total volume was measured. Saliva samples were centrifuged at 1000 rpm (MSE Harrier 18/80, UK) for 2 min to separate any food debris [Martínez-Mier et al., 2011]. Each blood sample was centrifuged for 10 min at 1500 rpm and the plasma collected. Nail samples from each participant (finger-and toenails , separately) were weighed, and then surface contamination from the nail clippings was removed by sonication in distilled water for 15 min [Whitford, 2005]. The cleaned samples were dried at 95ºC and weighed again. Food samples were weighed and then homogenised using an industrial blender (Cookwork BL9292, UK). Water and urine samples were analysed directly using a F ion selective electrode (ISE, 720A series; Orion Research Inc., Boston, MA, USA) after addition of TISAB III [Martínez-Mier et al., 2011]. Food, toothpaste, plasma, whole saliva, hair and nail samples were analysed after overnight hexamethyldisiloxane-acid diffusion [Martínez-Mier et a...

Dental Fluorosis according to Birth Cohort and Fluoride Markers in an Endemic Region of Colombia

“…e analyzed samples showed significant F concentration variability, with salty snacks and food seasoning presenting the highest concentrations. ese findings concur with those from other studies, in which there is no direct correlation between the various analyzed sources, F concentration, and DF severity in endemic regions [16,26,31]. In Colombia, F concentration in salt has also shown a high variability and sometimes may exceed the maximum permitted level [16,32].…”

“…Buzalaf et al [23] found a higher mean F concentration (4.22 (2.45) μg F/g). Similarly, in regions with low F in water, Idowu et al [26] found F concentrations of 3.237 (2.636) and 3.378 (2.197) μg F/g in fingernails and toenails, respectively. Also, the F concentration found in our study population is very low compared to areas with higher F in water, where F concentrations in nails of 10.420 (3.761) and 10.371(3.907) μg F/g have been reported [26].…”

“…And also, this study design cannot demonstrate a temporal connection between the F toenail concentration and the DF onset; however, it aligns with the high DF prevalence (96.6%) found in this population. e F concentration shows the F intake level over a long period, which can be useful for DF risk assessment [7,14,26]. However, the age group of the studied cases is outside the window of susceptibility, and therefore, age is crucial when predicting or assessing the risk for DF.…”

Biomarkers for the Assessment of Exposure to Fluoride in Adults

“…Recently, we published a comprehensive study that investigated the value of various F biomarkers in 2 groups of children living in areas of Nigeria with low-and high concentrations of F in the drinking water, respectively [Idowu et al, 2020]. Daily urinary F excretion (UFE) and F concentrations in plasma, whole saliva, hair and nails (fingernails and toenails) were measured and related to total daily F intake (TDFI) values evaluated by questionnaire.…”

“…The present work involved adults, for which less published data is available than for children. The work reported is related to the previous study on children [Idowu et al, 2020]. Data for adults were not included in that report, mainly to be able to discuss the findings for each age group more clearly, which would not have been possible in a combined condensed report.…”