Environmental and Individual Factors Associated with Nail Fluoride Concentration

Abstract

Nails have been suggested as suitable biomarkers of exposure to F, with the advantage of being easily obtained. The effect of water F concentration, age, gender, nail growth rate and geographical area on the F concentration in the fingernail and toenail clippings were evaluated. Volunteers (n = 300) aged 3–7, 14–20, 30–40 and 50–60 years from five Brazilian communities (A–E) participated. Drinking water and nail samples were collected and F concentration was analyzed with the electrode. A reference mark was made on each nail and growth rates were calculated. Data were analyzed by ANOVA and linear regression (α = 0.05). Mean water F concentrations (± SE, mg/l) were 0.09 ± 0.01, 0.15 ± 0.01, 0.66 ± 0.01, 0.72 ± 0.02, and 1.68 ± 0.08 for A–E, respectively. Mean F concentrations (± SE, mg/kg) ranged between 1.38 ± 0.14 (A, 50–60 years) and 10.20 ± 2.35 (D, 50–60 years) for fingernails, and between 0.92 ± 0.08 (A, 14–20 years) and 7.35 ± 0.80 (E, 50–60 years) for toenails. Among the tested factors, geographical area and water F concentration exerted the most influence on finger- and toenail F concentrations. Subjects of older age groups (30–40 and 50–60 years) from D and E showed higher nail F concentrations than the others. Females presented higher nail F concentration than males. Water F concentration, age, gender and geographical area influenced the F concentration of finger- and toenails, and hence should be taken into account when using this biomarker of exposure to predict risk for dental fluorosis.