UC Irvine

Groups of rats inhaled mixtures of O3 and acid particles for three hours while exercising. One group received purified air, a second group breathed 0.6 ppm O3, a third group breathed a mixture: SO2 (5 ppm) plus sulphuric acid aerosol containing iron and manganese ions (1 mg/m3, 0.5 µm mass median aerodynamic diameter). The fourth and fifth groups breathed the above mixture plus 0.6 ppm O3; group 4 was exposed while exercising and group 5 was exposed at rest. Tritiated thymidine (3HT) was injected into the rats 17 hours post-exposure; lungs, trachea, and nasal airways were fixed and sectioned. Focal lesion areas were measured in the parenchyma and3HT uptake by replicating cells in the upper airways was determined by autoradiography. Significant amounts of label were incorporated by squamous and respiratory epithelia of the nose, but little uptake was observed in the olfactory or tracheal tissue. In the squamous tissue none of the exposures resulted in labelling rates in excess of those observed in rats exposed to purified air. In respiratory epithelium, however, the acid-containing multicomponent atmospheres significantly increased labelling rates above background in animals exposed while exercising. O3 alone did not affect3HT uptake, nor did the presence or absence of 03 in the multicomponent atmosphere alter the observed uptake rates. © 1988 The British Occupational Hygiene Society.