Respiratory Irritation Associated with Inhalation of Boron Trifluoride and Fluorosulfonic Acid

Abstract

The objectives of this study were to examine the respiratory irritancy of boron trifluoride (BF₃) and fluorosulfonic acid (FSA) following acute inhalation exposure. Testing was conducted using groups of 10 male and 10 female rats (BF₃) or groups of 6 male rats (FSA). Rats were exposed for a single 4-h period (BF₃) or a single 1-h period (FSA) and necropsied 1 or 14 days after exposure (BF₃) or 14 days after exposure (FSA). Measurements consisted of clinical signs, body weight, kidney and lung weight, histopathology (BF₃), 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/m³ BF₃, 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/m³ BF, was considered a no-observed-adverse-effects level (NOAEL). A concentration of 4125 mg/m³ 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/m³ 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 BF₃ indicated that respiratory irritation was present at a level of 74.4 mg/m³ whereas 24.6 mg/m³ was a NOAEL. A single 1-h exposure to 845 mg/m³ 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.