Histological structure of rat lung. (A and B) Effect of low dose of malathion and metalaxyl showing normal structure. (C) Effect of low dose of cymoxanil showing slight interstitial mononuclear cells infiltration (arrow). (D) Effect of medium dose of malathion showing marked thickening in the interalveolar septa (arrow). (E) Effect of medium dose of metalaxyl showing slight interstitial pneumonia (arrow). (F) Effect of high dose of malathion showing more marked interstitial nephritis (arrow). (G) Effect of high dose of malathion showing, massive peribronchial infiltration of mononuclear cells (arrow). (H) Effect of with high dose of metalaxyl showing slight interstitial pneumonia (arrow). (I) Effect of high dose of cymoxanil showing marked interstitial mononuclear cells infiltration (triangle) and pneumocyte type II hyperplasia (arrows). Stain: H and E. Magnification bar: 50 µm.