Three projects will be undertaken during the coming year: 1. Further studies as to individual variation in response to SO2 will be undertaken. Specifically: will those chickens, which fail to slow their mucociliary rates at relatively low dosages, continue to fail to respond each time they are exposed to that same dose? Will responders at the level of 6 parts/million respond to lower doses? Finally, the reason for this difference will be sought. Is it due to anatomical variations in the upper respiratory chamber? Physiological differences in mucus? 2. Although the combination of SO2 exposure and Newcastle disease virus has been studied, all virus inoculation was by the intranasal inoculation of a small volume of fluid to an unanaesthetized chicken. In order to simulate the natural conditions of respiratory agent spread, large droplet aerosol inoculation will be studied. Preliminary experiments with aerosolized dye show this to be practicable. 3. Exposure of chickens to SO2 slows the mucociliary transport rate. Our belief is that this slowing is related to the formation of anchoring lines of mucus which extend from the acinar gland cells out to the mucus layer. In order to test whether this may be seen physiologically, we are currently studying with Dr. David Swift of the Department of Environmental Health Sciences the degree to which iron particles embedded in the mucus may be moved by the induction of a magnetic field. This might allow the question of increased viscosity to be separated from one of increased adherence of the blanket to the mucus secreting cells.