A 40-year-old construction worker has noted increasing shortness of breath and cough over many years. On physical examination bilateral inspiratory crackles are heard. Chest x-ray shows eggshell calcifications in hilar adenopathy and bilateral small nodular interstitial markings in the upper lobes.

The 40-year-old construction worker provides an example of environmental lung disease. Silicosis is caused by the inhalation of crystalline silica. Occupations typically at risk include cement workers and sandblasters. These workers should be provided with respiratory protection such as a respirator. Usually, a latency period of 10 to 15 years from first exposure is required for the disease process to become evident. Asbestosis, another occupational lung disease, affects lower lobes (rather than the predominantly upper lobe involvement of silicosis). Asbestosis causes pleural disease, whereas silicosis causes lymphadenopathy.