Pulmonary changes in the rat following low phosgene exposure.

Minimal inhalation doses (or concentrations) of phosgene necessary for the production of changes within the blood-air barrier were determined in rats. At least 50 ppm.min (5 ppm X 10 min) was necessary for the production of alveolar oedema (the minimal effective phosgene concentration being 5 ppm). While the smallest phosgene dose to produce an increase in pulmonary lavage protein content was also 50 ppm.min and while the smallest phosgene dose to produce widening of pulmonary interstices was 25 ppm.min, there was no phosgene threshold concentration (down to 0.1 ppm) for these two latter parameters, which are assumed to be indicators of physiological compensatory mechanisms within the blood-air barrier. The primary localisation of pulmonary damage seemed to depend on the concentration of phosgene used: at low concentrations (0.1-2.5 ppm) the changes were primarily located at the transition from terminal bronchioles to the alveolar ducts; at higher concentrations (5 ppm) damage to the alveolar pneumocytes (type I) was more conspicuous.