title: Diesel exhaust is a pulmonary carcinogen in rats exposed chronically by inhalation.
abstract: Male and female F344 rats were exposed 7 hr/day, 5 day/week for up to 30 months to automotive diesel engine exhaust at soot concentrations of 0.35, 3.5, or 7.0 mg/m3 or were sham-exposed to clean air. Rats were terminated at 6-month intervals to measure lung burdens of diesel soot and for histopathology. Other rats either died or were terminated after 30 months of exposure. Lungs were fixed, sectioned into 3-mm slices, and examined by a dissecting microscope to detect tumors. Lesions were stained and examined by light microscopy. Survival and body weight were unaffected by exposure. Focal fibrotic and proliferative lung disease accompanied a progressive accumulation of soot in the lung. The prevalence of lung tumors was significantly increased at the high (13%) and medium (4%) dose levels above the control prevalence (1%). Four tumor types, all of epithelial origin, were observed: adenoma, adenocarcinoma, squamous cyst, and squamous cell carcinoma. Logistic regression modeling demonstrated a significant relationship between tumor prevalence and both exposure concentration and soot lung burden. These results demonstrate that diesel exhaust, inhaled chronically at a high concentration, is a pulmonary carcinogen in the rat.
mesh_terms: D000230:Adenocarcinoma / Q000139:chemically induced / Q000473:pathology / Q000503:physiopathology; D000280:Administration, Inhalation; D000818:Animals; D001822:Body Burden; D001835:Body Weight / Q000187:drug effects; D002294:Carcinoma, Squamous Cell / Q000139:chemically induced / Q000473:pathology / Q000503:physiopathology; D005260:Female; D008168:Lung / Q000473:pathology; D008175:Lung Neoplasms / Q000139:chemically induced* / Q000473:pathology / Q000503:physiopathology; D008297:Male; D051381:Rats; D011916:Rats, Inbred F344; D012129:Respiratory Function Tests; D001335:Vehicle Emissions / Q000633:toxicity*
chemical_list: D001335:Vehicle Emissions