During a spirometry screening program in a factory, a 38-year-old worker exposed to silica dust for 15 years shows FEV₁ 70% predicted, FVC 55% predicted, and FEV₁/FVC ratio 0.78. What is the most common cause of this restrictive spirometry pattern in occupational lung disease?

Explanation

## Restrictive Spirometry in Occupational Lung Disease **Key Point:** A restrictive pattern (FEV₁/FVC >0.70 with reduced FEV₁ and FVC) in a worker with occupational exposure points to pneumoconiosis. Silicosis is the most common occupational pneumoconiosis globally and in India. **High-Yield:** Silicosis is caused by inhalation of crystalline silica dust (SiO₂). It is the most frequent occupational lung disease in India, particularly in mining, foundry, and stone-cutting industries. The restrictive pattern reflects pulmonary fibrosis. ### Restrictive Pattern Differential in Occupational Exposure | Pneumoconiosis | **Exposure** | **Prevalence in India** | **Latency** | **Fibrosis Pattern** | |---|---|---|---|---| | **Silicosis** | Crystalline silica (mining, stone-cutting) | Very high | 10–20 years | Upper lobe nodular | | **Asbestosis** | Asbestos fibers (insulation, shipyards) | Moderate | 15–40 years | Lower lobe pleural | | **Coal worker's pneumoconiosis** | Coal dust (coal mining) | Lower in India | 10–20 years | Upper lobe nodular | | **Talcosis** | Talc dust (rare in India) | Very low | Variable | Diffuse nodular | **Clinical Pearl:** Silicosis is endemic in India due to widespread stone-cutting, slate mining, and foundry work. The 15-year exposure history and restrictive pattern in this case are classic. Chest X-ray would show "eggshell" hilar lymphadenopathy and upper lobe nodules. **Mnemonic: Pneumoconiosis Epidemiology — "SACT"** - **S**ilicosis — most common occupational lung disease - **A**sbestosis — pleural-predominant fibrosis - **C**oal worker's pneumoconiosis — coal miners - **T**alcosis — rare, cosmetic/talc powder exposure [cite:Park 26e Ch 10]