Asbestos Exposure Results in Asbestosis and Usual Interstitial Pneumonia Similar to Other Causes of Pneumoconiosis

The progression of asbestosis is supposed to begin with the first order of respiratory bronchiole and extend outward. Recently, grade 4 asbestosis was reported to begin with the subpleural peripheral lobular area or the subpleural lobule. Grade 4 asbestosis is defined as diffuse pulmonary fibrosis caused by the inhalation of excessive numbers of asbestos fibers. Pathologically, the presence of more than two asbestos bodies/cm 2 on a glass slide is required. There are many cases of diffuse interstitial pneumonia, mainly usual interstitial pneumonia, that does not fulfill the above criteria among asbestos workers or high-grade environmentally exposed persons. I call these cases “usual interstitial pneumonia seen in asbestos workers” and not idiopathic pulmonary fibrosis. In this chapter, I discuss the above subjects, including the dose-response relationship for asbestos exposure, the heterogeneous response to asbestos exposure, and the relationship between asbestosis and idiopathic pulmonary fibrosis.