The histopathology of rat lung following short term exposures to mixed oxides of nitrogen (NOx).

The histopathology of rat lung after exposure to high concentrations of mixed oxides of nitrogen (NOx) has been studied. Considerable damage was observed, which initially took the form of 'thickening' and 'blebbing' of the alveolar epithelium and disruption of type II pneumocytes. These early changes were attributed to the direct effect of the oxidant action of NOx. There then followed a latent period of approximately 6 h after which the development of oedema of the interstitium and alveolar septum was observed. Clinical observations and the results from light and electron microscopical examination suggested that the lung damage caused by exposure to 518 parts/10(6) NOx for 5 min was greater than that caused by 1435 parts/10(6) for 1 min. This was not supported by the findings from light microscopy where similar damage was observed at both dose levels. These results suggest that such exposures might pose a risk of lung damage to man.