There are in literature many reports of human death due to acute fluoride (F) poisoning and some of them involved suicide. Objectives: To evaluate the viability of using nails and bone surface as indicators of acute exposure to F. Methods: Six groups of 10 rats, aging 70 days, received, by gastrogavage, single doses of NaF containing 10, 35, 45, 60, 75 and 90 mg F/kg body weight. Control group received deionized water. Two hours after, rats were killed and their plasma, nails (halves near to the growth end) and femur were collected. Nail and plasma F concentrations were analyzed with the ion specific electrode (Orion 9409) following HMDS-facilitated diffusion. Fluoride at femur surface was removed from a circular area (4.52 mm2) by immersion in 0.5 M HCl for 15 seconds, buffered with Tisab (containing NaOH) and analyzed with the ion specific electrode (Orion 9609). Data were analyzed by ANOVA and Tukey's test (p<0.05) and by linear regression (p<0.001). Results: Fluoride concentrations (ppm) ranged from 55.377 to 91.498; from 0.019 to 6.937 and from 2,468 to 9,579 for nails, plasma and femur surface, respectively. Fluoride concentration in nails from experimental groups was not different from control. Regarding plasma F, all experimental groups differed from control, except the group that received the lowest dose. In respect to femur surface F, only the group that received the highest dose differed from control. A strong correlation was found between plasma F and the dose administered (r=0.736) and medium correlations were found between femur surface and the dose administered (r=0.503) and femur surface and plasma F (r=0.500). Conclusions: Data suggest that two hours after F administration, nails and femur surface are not good indicators of acute exposure. Additional studies, in which samples were collected longer periods after exposure to F, should be done.

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