Systemic fluoride poisoning following dermal hydrofluoric ACID exposure: Development of an intravenous sodium fluoride infusion model in rats

The effect of dermal exposure to concentrated (48% w/v) hydrofluoric acid (HF) on survival and plasma fluoride concentration was investigated in rats. Results of dermal exposure to abdominal and back skin were compared with intravenous administration of sodium fluoride. Dermal HF exposure on 6 cm² for 5 min resulted in toxic plasma fluoride concentrations. The location of application on the body influenced both the survival time of the rats and the kinetics of plasma fluoride concentrations. After abdominal application of 0.25 or 0.5 ml HF, a 50% mortality rate within 300 min (time of death between 75 and 270 min) was observed. After application of 0.25 ml HF on the back all rats survived the 315 min observational period while after application of 0.5 ml HF an LD₅₀ was reached (time of death between 280 and 314 min). Abdominal exposure caused a gradually increasing plasma fluoride concentration while after exposure on the back a rapid increase of the plasma fluoride concentration was observed, followed by a gradual decrease to a relative constant level. It is concluded that, after the initial exposure of the back, the back skin tissue layers act as a slow-release storehouse of fluoride. The course of plasma fluoride concentrations after skin exposure of the back to 0.5 ml HF could be simulated by a two-phase sodium fluoride infusion model. A loading dose of 1.2 mmol/kg/h during 30 min is followed by a maintenance dose of 0.3 mmol/kg/h.