Pathologic processes can involve any part of the lungs, including the Airways (eg, in occupational asthma, reactive airways dysfunction syndrome, toxic inhalations, air pollution-related illness, or byssinosis) Lung parenchyma (eg, in pneumoconioses, hypersensitivity pneumonitis, or silicosis) Pleura (eg, in asbestos-related diseases) Environmental inhalation exposure has long been known to be a risk factor for asthma (see Occupational Asthma), but it is also increasingly being recognized as a non-smoking cause of COPD (chronic obstructive pulmonary disease).