ABSTRACT
Lung cancer is the most frequent cause of cancer fatalities in the United States, and the incidence of lung cancer has been rising for at least 50 years. Rats develop lung tumors after inhalation of human lung carcinogens in all instances where they were tested except for one. Complex mixtures that are known rodent pulmonary carcinogens include atmospheres that contain particles with several, if not hundreds, of organic and inorganic chemicals and various gases that may be toxic or carcinogenic. In all mouse strains the vast majority of lung neoplasms are adenoma or adenocarcinomas. Particle overload has been described most often in rats, but has also been noted in mice and Syrian hamsters. Rats respond differently than other species to the overload of particles in the lung. Adverse effects observed in rats with particle overload include chronic inflammation, septal fibrosis, alveolar proteinosis, epithelial hyper-plasia, squamous metaplasia, and benign and malignant lung neoplasms.
