Abstract
Mice were exposed to an aerosol of a polyphenyl reactor coolant for several hours daily up to eight days. The oil concentration was comparable to that measured in the atmosphere at the reactor site. No evidence of lung injury was detected by light microscopy. At the ultrastructural level, many type 2 alveolar epithelial cells showed central vacuolation of mitochondria. These ceils exhibited the normal turnover time of around 35 days. Following the cessation of aerosol exposure, the succeeding generation of epithelial cells showed no abnormality.