Complicated Silicosis Diagnosed 12 Years After Exposure Cessation: Lessons Learned from Gaps in Occupational Health Surveillance

Abstract

Silicosis is an occupational lung disease caused by prolonged inhalation of respirable crystalline silica and remains a major global public health concern. Despite advances in occupational health practice and dust control measures, new cases continue to occur, particularly in developing countries. We report the case of a 67-year-old Thai man who had worked in a refractory brick factory for 23 years as a stone crusher operator without appropriate respiratory protection. Twelve years after cessation of occupational exposure, he was diagnosed with complicated silicosis during a routine health examination. Chest radiography demonstrated diffuse small nodular opacities throughout both lungs with bilateral upper-lung mass-like opacities. Although lung biopsy is not routinely required for the diagnosis of silicosis, it may be indicated when radiological findings are inconclusive or when alternative diagnoses, particularly pulmonary tuberculosis or lung cancer, cannot be confidently excluded. In this patient, chest computed tomography was unable to reliably differentiate complicated silicosis from pulmonary tuberculosis or lung malignancy. Consequently, bronchoscopy with transbronchial lung biopsy was performed and histopathological examination revealed silicotic nodules, confirming the diagnosis. This case highlights important deficiencies in the occupational health surveillance system, including the lack of a comprehensive and continuous surveillance program extending from pre-employment through post-employment. These gaps likely contributed to delayed diagnosis despite the patient's prolonged occupational silica exposure. This case underscores the importance of implementing systematic chest radiographic surveillance before employment, periodically during employment, at the time of employment termination, and after exposure cessation among workers with a history of silica exposure to facilitate early disease detection. In addition, interpretation of chest radiographs by physicians trained in the ILO International Classification of Radiographs of Pneumoconioses, such as certified NIOSH B Readers, should be promoted to improve diagnostic accuracy. Strengthening occupational health surveillance programs is essential for the early detection and prevention of advanced silicosis and will contribute to the national goal of eliminating silicosis in Thailand.