Fingernails and toenails as biomarkers of subchronic exposure to fluoride from dentifrice in 2- to 3-year-old children.

This work evaluated the use of fingernails and toenails as biomarkers of subchronic exposure to fluoride (F) from fluoride dentifrice (FD) in 2- to 3-year-old children. Ten 2- to 3-year-old children used a placebo dentifrice (without F) for 28 days, FD (1,570 ppm F as monofluorophosphate) for the following 28 days, and then placebo dentifrice for an additional 28 days, then returned to their usual dentifrices. Fingernails and toenails were clipped every 2 weeks, during the experimental period and for an additional 22 weeks. Nail F was analyzed by electrode following hexamethyldisiloxane-facilitated diffusion. There were no significant differences between fingernail and toenail F concentrations. Mean peak F concentrations occurred 16 weeks after starting the use of FD. Results suggest that fingernails and toenails may be suitable biomarkers of subchronic exposure to F from FD in small children.