When acute exposure to fluoride is thought to be the cause of death, confirmation often depends on the analysis of some body fluid or tissue. The aim of this study was to evaluate the use of nails and the periosteal surface of bone as indicators of acute exposure to fluoride. Six groups of rats were given a single oral dose of fluoride (50 mg/kg body weight), while the control group was given deionized water. The rats were killed at 2, 4, 8, 16, 24, and 48 h after fluoride administration. Plasma and nails (the proximal halves) were collected and analyzed for fluoride with an ion-specific electrode after hexamethyldisiloxane-facilitated diffusion. A circular area of the femur (4.52 mm(2)) was etched with 0.5M HCl for 15 s, and, after the addition of a buffer, the solution was analyzed with an ion-specific electrode. Peak plasma concentration occurred at 2 h, followed by progressively declining concentrations. Peak nail fluoride concentrations occurred at 8 h. The mean nail concentrations at 8, 16, and 24 h were significantly higher than that of the control group. Bone surface concentrations were significantly higher than that of the control group at 4 h and thereafter. Thus, the proximal portion of nails and bone surface are suitable biomarkers for acute fluoride exposure in rats.
Finally, in our 48-h study, we found that bone surface fluo- ride concentrations increased sooner than those in the nails and that they did not decline as they did in nails. This suggests that fluoride accumulation on the periosteal surface of the femur is faster and less likely to change as a function of time. For these reasons, we believe that this region of the femur is probably a better biomarker to confirm exposure to large doses of fluoride.