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 (COF2).Methods: Rats from both sexes were exposed for durations of 5 and 10min to nominal concentrations of 10,000 to 57,000ppm HF or 500 to 10,000ppm COF2. 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 COF2 10-min LC50's were 48,661ppm and 1083ppm, respectively. HF mortalities were generally delayed 3 to 4 days post-exposure, while COF2 mortalities occurred during or briefly after exposure. Lung fluoride levels increased with COF2 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 COF2 is nearly 45 times more lethal than HF in rats.Conclusions: These experiments suggest that hydrolysis to HF cannot solely explain COF2 toxicity. Although HF and COF2 may have common injury mechanisms, they are expressed to markedly different degrees and temporal occurrence.