<prompt> A 60-year-old man has had worsening dyspnea and nonproductive cough over the past 2 years. On physical examination, his temperature is 37.4degC, pulse is 74min, respirations are 20min, and blood pressure is 11070 mm Hg. A chest radiograph shows extensive interstitial lung disease and a prominent right-sided heart border. Spirometry reveals decreased FEV1 and FVC. His pulmonary disease is most likely caused by exposure to which of the following?Carbon monoxideFungal hyphaePlant pollenSilica crystals  <response>: His pneumoconiosis with progressive massive fibrosis is producing restrictive lung disease. Silicosis occurs from prolonged and extensive exposure to inorganic dusts in occupations such as mining. Carbon monoxide poisoning produces hypoxemia without pathologic changes to lung tissues. Fungal hyphae may produce either an allergic response or a hypersensitivity pneumonitis. Plant pollens are most often associated with episodic atopic asthma. Sulfur dioxide contributes to chronic bronchitis. Wood dusts tend to produce bronchoconstriction. 