Short-term inhalation toxicity of perfluoroisobutylene.

Perfluoroisobutylene (PFIB) is a highly toxic, colorless gas. The 4-hour Approximate Lethal Concentration in male rats is 0.5 ppm (v/v). The median lethal concentration (LC50) was calculated for groups of 10 male Crl:CD rats, exposed, nose-only, for either 0.25, 0.50, 1, 2, 5, or 10 minutes to various concentrations of PFIB. Atmospheric concentrations of PFIB were determined by gas chromatography (electron capture detector). No mortalities or signs of respiratory irritation were seen during exposure. Weight loss and respiratory impairment were evident up to 48 hours post-exposure. Affected rats either died with gross pathological signs of pulmonary congestion or recovered with no apparent residual effects. The 0.25-minute LC50 was 361 ppm (321--415 ppm, 95% Confidence Limits); the 10-minute LC50 was 17 ppm (15--19 ppm, 95% Confidence Limits). The steep slope of the concentration-mortality curve at each time interval reflected the narrow range of concentrations that produced mortality (LC1-LC99). In addition, a "Concentration x Time = Constant" relationship was apparent from 0.25 to 10 minutes.