Health effects of sulfur-related environmental air pollution. V. Lung structure

The lungs of 8 male beagle dogs were examined morphologically and morphomet rically after exposure for 13 mo to a respirable sulfur(IV) aerosol at a ma ss concentration of 1.53 mg m(-3) (16.5 h/day), and to an acidic sulfate ae rosol carrying 15.2 mu mol m(-3) hydrogen ions into the lungs (6 h/day). An additional eight dogs served as unexposed controls. Standard morphometric analyses of both the surface epithelia of the conducting airways and the al veolar region were performed. These analyses showed no difference between t he exposure group and control group. However, there was a tendency to an in crease in the volume density of bronchial glands in the exposure group. Fiv e of eight exposed animals showed thickened ridges (knob-like structures) a t the entrance to alveoli in the alveolar duct and alveolar sac. Transmissi on electron microscopy revealed that the thickening was mainly due to type II cell proliferation. As the previous experiment using sulfite aerosol onl y showed no alterations in the proximal alveolar regions, the changes obser ved may be considered as effects of acidic sulfate aerosol alone or in comb ination with sulfite. These findings suggest that sulfur aerosols have the potential to induce epithelial alterations in the proximal alveolar region, which is a primary target for air pollutants.