Abstract
Harmful effects of diesel exhaust particles on the lungs, especially tumorgenesis, had been reported in our previous experiments. In order to reconfirm the previous study and to determine the dose-response relationship of instilled diesel particles on rats' lungs, another instillation experiment was carried out.
Diesel exhaust particles were collected from a small sized engine (2400), and suspended particles were intratracheally instilled in the F344 (SPF), female rat's lung. 0.125 mg of diesel particles were instilled in group 1, 0.5 mg in group 2, 2 mg in group 3, and 8 mg in group 4...Group 5 was for control.
Animals were examined at 2 and 2.5 years after the instillation. No pathological changes were seen in the lungs of group 1 and 2. Mild inflammatory changes in the lung and a small number of lung tumors (3/47, 6%) were observed in group 3.
In group 4 large amount of diesel particles remained in the lungs accompanying with many foci of epithelial hyperplasia and focal fibrosis. Twenty-four among 56 rats (43%) had 40 lung tumors (12 adenomas and 28 carcinomasi). A statsitically significant number of lung tumors was found in group 4 compared with group 5 (2/ 48, 4%) and group 3 (3/47).
It is concluded that diesel particles are harmful to the lungs, and cause lung cancer in a dose-response relationship.
