Regional deposition and absorption of inhaled hydrogen fluoride in the rat

Abstract

The regional deposition of inhaled hydrogen fluoride (HF) was investigated by drawing known amounts of this irritant gas through the surgically isolated upper respiratory tract of anesthetized rats, while each animal respired HF-free room air through an endotracheal tube. At HF concentrations ranging from 30 to 176 mg F/m 3, greater than 99.7% of the HF drawn into the upper respiratory tract was removed from the airstream during passage through that site. Plasma fluoride concentrations were significantly elevated by this upper respiratory tract exposure to HF and were highly correlated with airborne HF concentrations ( r (8) = 0.98, p < 0.01). For comparative purposes, intact anesthetized rats were subjected to nose-only exposure to 63 mg F/m 3 HF for 1 hr. Both pulmonary and plasma fluoride concentrations were significantly elevated over control levels by nose-only exposure; however, pulmonary fluoride concentrations in these rats were no higher than plasma fluoride concentrations, providing little evidence that airborne HF penetrates to the lungs of rats respiring normally. These results indicate that in the anesthetized rat virtually all inhaled HF deposits in the upper respiratory tract from which it may be absorbed and/or translocated to other sites, e.g., the gastrointestinal tract, where systemic absorption may occur.