| Abstract: | Artificial stone slabs, composed of quartz sands and resin, are commonly used for kitchen and bathroom countertops. Workers handling this material are exposed to high levels of respirable crystalline silica (>90%) and have experienced an increase in silicosis cases with rapid disease onset within ten years of exposure.1 Diagnosis entails exposure history, radiographic detection, and exclusion of other causes. Chest computed tomography (CT) is more effective than X-ray for early diagnosis and preventing complicated silicosis. Reported CT findings associated with artificial stone-related silicosis range from non-specific indicators, such as ground-glass opacities, linear and irregular opacities, emphysema, and mediastinal lymphadenopathy, to more characteristic manifestations like centrilobular nodular opacities predominantly in the upper-posterior lung, nodular conglomeration, and large opacities with surrounding cicatricial emphysema.2 Following approval from the institutional review board at the National Taiwan University Hospital and informed consent from participants, a low dose chest CT examination was performed on 19 workers engaged in the production of artificial stone. Among these individuals, 12 exhibited abnormal CT opacities, and four displayed subpleural curvilinear lines in their upper lobes (Fig. 1). The estimated exposure levels to respirable crystalline silica for these four individuals (subjects 1–4) were 0.27, 0.77, 4.44, and 4.44 mg/m³, respectively, resulting in cumulative exposures of 1.35, 2.30, 13.32, and 26.64 mg/m³-year (Table 1). Subjects 1, 3, and 4 were raw material operators who blended quartz sand, resin, curing agents, and additives, and then molded these materials into the desired form. Subject 2 operated a water-suppressed grinding or polishing machine to customize and process artificial stone slabs. All four cases exhibited ground-glass opacities and scattered nodules. Chest X-rays revealed abnormalities only in subjects 1 and 4, both of whom also demonstrated large opacities. Lung function, including forced (forced expiratory volume at one second, FEV1; forced vital capacity, FVC) and static measures (total lung capacity, TLC; residual volume, RV), as well as diffusion capacity for carbon monoxide (DLco), was evaluated using spirometry, plethysmography, and single-breath methods. The Global Lung Initiatives calculator for Southeast Asian ethnicities (https://gli-calculator.ersnet.org/) was utilised to estimate predicted values and the lower limit of normal (LLN, 5th percentile). Subject 2 exhibited a mild obstructive ventilatory defect, characterised by an FEV1/FVC ratio less than the LLN. Subjects 1, 3, and 4 presented a mild restrictive ventilatory defect, as indicated by a TLC less than the LLN. All four subjects demonstrated mildly impaired diffusion capacity, defined by a DLco below the LLN. Both Subject 3 and Subject 4, who had a history of cigarette smoking, reported cumulative smoking quantities of 1.23 and 3.14 pack-years, respectively. All four subjects reported no underlying, physician-diagnosed conditions such as pulmonary tuberculosis, asthma, hypertension, cardiac disorders, diabetes, or autoimmune diseases. During field investigations, discrepancies were observed in the workers' adherence to proper respiratory protective equipment usage. This could potentially explain the absence of a clear linear relationship between exposure and imaging results for subjects 1 to 3. |
