EXPOSURE TO HYDROGEN-FLUORIDE - AN EXPERIMENTAL-STUDY IN HUMANS OF CONCENTRATIONS OF FLUORIDE IN PLASMA, SYMPTOMS, AND LUNG-FUNCTION

Objectives--To study the absorption of inhaled hydrogen fluoride (HF) by measuring plasma fluorides and HF concentrations in the breathing z one during exposure to HF. A possible dose-effect relation was investi gated by following airway symptoms and lung function--that is, forced expiratory volume in one second (FEV(1)) and forced vital capacity (FV C)--during and after exposure to HF. Methods--20 healthy, male volunte ers were exposed for one hour to constant HF concentrations that range d from 0.2 to 5.2 mg/m(3); these concentrations are known to occur amo ng potroom workers in the primary aluminium industry. Plasma fluorides were analysed before, during, and after exposure. Symptoms from the e yes and the upper and lower airways were registered and graded from 1 to 5 with a standardised questionnaire. Results--The total symptom sco re was significantly increased at the end of exposure for all the subj ects as a group (P < 0.01) and for the group exposed to HF below the p resent Norwegian standard for total fluorides 0.6 mg/m(3) (P = 0.05). No change was detected in FEV(1), although a significant decrease was found in FVC in the group exposed to fluorides below th hygienic stand ard (n = 9) and for the entire group (n = 23). Almost all the symptoms had disappeared four hours after the end of exposure. Symptom scores from the upper airways were significantly correlated with the HF conce ntration (r = 0.62, P = 0.002), the change in plasma fluoride concentr ation (Delta C) (r = 0.51, P = 0.01), and the maximum plasma fluoride concentration (C-max) (r = 0.42, P = 0.05). A significant correlation was also found between the total symptom score for airways and the HF concentration. Conclusions--The present study showed a strong relation between inhaled HF and concentrations of fluoride in plasma. Upper ai rway and eye symptoms occurred after one hour of exposure to HF even w hen below the Norwegian hygienic standard for fluorides.