Impact of skin temperature and intradermal pH on transdermal fluoride absorption following hydrofluoric acid exposure: An ex vivo diffusion cell study in human skin

Accidents involving hydrofluoric acid (HF) can cause systemic poisoning due to the transdermal absorption of fluoride ions. The present study investigates the impact of skin temperature and intradermal pH on fluoride absorption and its kinetics. Human skin was exposed to 30 % HF for 3 minutes using a static diffusion cell model. The study compared cumulative fluoride absorption at two different skin temperatures (24°C and 32°C) and two intradermal pH values (6.5 and 7.2). Experiments were performed at least three times per treatment and per donor (n = 5), over a duration of 8 h and 12 h for pH and temperature experiments, respectively. Results showed that fluoride absorption increased with temperature, with a ∼17.8 % increase in cumulative penetration at 32°C compared to 24°C. The maximum flux rate through the skin was reached within the first hour and was ∼54 % lower at 24°C. Additionally, acidifying the skin to an intradermal pH of 6.5 led to a significant increase in cumulative fluoride absorption by ∼12.6 % and a ∼50.3 % increase in the maximum flux rate. The findings suggest that reducing fluoride absorption after accidental skin contact with HF may be achieved by lowering skin temperature and buffering intradermal pH to a physiological level. These results have important implications for first-aid measures in real-life scenarios involving HF exposure. Controlling skin temperature by cooling and intradermal pH with the addition of buffering agents may enhance decontamination strategies.