Morbidity and mortality resulting from acute inhalation exposures to hydrogen fluoride and carbonyl fluoride in rats.

Objective: Experiments were undertaken to compare morbidity and mortality from brief inhalation exposures to high levels of hydrogen fluoride (HF) and carbonyl fluoride (COF ₂ ).
Methods: Rats from both sexes were exposed for durations of 5 and 10 min to nominal concentrations of 10,000 to 57,000 ppm HF or 500 to 10,000 ppm COF ₂ . Respiration was monitored before, during, and after exposure. Animals were observed up to 6 days post-exposure. Terminal blood samples were collected for routine clinical chemistry and hematology. Post-mortem lung fluoride concentrations and lung weights were measured, and gross pathology noted.
Results: Both gases produced respiratory depression independent of concentration or exposure duration with minute ventilation decreasing to approximately 50% of baseline. Estimated mixed-gender HF and COF ₂ 10-min LC ₅₀ 's were 48,661 ppm and 1083 ppm, respectively. HF mortalities were generally delayed 3 to 4 days post-exposure, while COF ₂ mortalities occurred during or briefly after exposure. Lung fluoride levels increased with COF ₂ dose, though elevated lung weights occurred only at the mid-level exposures. Lung weights were unaffected in the HF-exposed animals, and their lung fluoride concentrations were variable. Clinical chemistry and hematology had few consistent trends with the exception of hemoconcentration primarily in HF-exposed males. These short-term exposure experiments conclude that COF ₂ is nearly 45 times more lethal than HF in rats.
Conclusions: These experiments suggest that hydrolysis to HF cannot solely explain COF ₂ toxicity. Although HF and COF ₂ may have common injury mechanisms, they are expressed to markedly different degrees and temporal occurrence.