Figure 5

Lung of SH rat exposed to 3 mg/kg (a) or 10 mg/kg (b) of RTD. A significant dose-effect relationship is seen for the number of macrophages loaded with PM after exposure to RTD. Slight to moderate quantities of PM are phagocytised by a small number of alveolar macrophages after exposure to the lower RTD dose (a; arrows) while exposure to 10 mg/kg of body weight of RTD resulted in a large number of alveolar macrophages loaded with PM mass (b; arrow). HE, magnification 500×.