Respiratory irritation associated with inhalation of boron trifluoride and fluorosulfonic acid.

The objectives of this study were to examine the respiratory irritancy of boron trifluoride (BF(3)) and fluorosulfonic acid (FSA) following acute inhalation exposure. Testing was conducted using groups of 10 male and 10 female rats (BF(3)) or groups of 6 male rats (FSA). Rats were exposed for a single 4-h period (BF(3)) or a single 1-h period (FSA) and necropsied 1 or 14 days after exposure (BF(3)) or 14 days after exposure (FSA). Measurements consisted of clinical signs, body weight, kidney and lung weight, histopathology (BF(3)), and breathing parameters (FSA) and were used to evaluate the possible irritating effects of these compounds. The results indicated treatment-related findings in the larynx and trachea in the rats exposed to 74.4 mg/m(3) BF(3), consisting of ventral cartilage necrosis, hemorrhage, and an increase in ventral epithelial hyperplasia and ventral inflammatory cell inflammation 24 h postexposure. In the animals sacrificed 14 days postexposure, the only notable observation was ventral cartilage necrosis, present in 2 animals. The next lower level tested, 24.6 mg/m(3) BF, was considered a no-observed-adverse-effects level (NOAEL). A concentration of 4125 mg/m(3) FSA resulted in a clearly decreased breathing rate during and shortly after exposure with 67% (4/6) mortality on days 5-9 after exposure. A concentration of 845 mg/m(3) FSA resulted in only minor signs of irritation, consisting of slight changes in breathing pattern shorlty after exposure. The results of the present 4-h inhalation study with BF(3) indicated that respiratory irritation was present at a level of 74.4 mg/m(3) whereas 24.6 mg/m(3) was a NOAEL. A single 1-h exposure to 845 mg/m(3) FSA resulted in only minor signs of respiratory irritation, indicating that on a mass basis FSA is no more toxic or irritating than hydrogen fluoride (HF) or sulfuric acid.