Follow-up of workers with silicosis related to quartz conglomerates

Introduction: Clusters of silicosis related to fabrication of quartz conglomerates have been recently reported. The prognosis of this form of silicosis has not been established. Aim: To evaluate the progression of silicosis in workers exposed to quartz conglomerate. Methods: A short-term follow-up of workers with silicosis was performed. Lung function tests, high resolution computed tomography (HRCT) and levels of airborne crystalline silica during activity in the finishing lines were assessed at diagnosis and after 12 months. Results: We studied 18 cases of silicosis (age at diagnosis: range 25-53 yr; duration of exposure to quartz conglomerate dust: 3.5-10 yr, and average workplace silica dust levels: 0.260-0.744 mg/m3). At diagnosis, 50% of subjects exhibited an impairment of DLco (75.7±15% predicted). The most common spirometric alteration (38% of cases) was a restrictive pattern based on TLC (5.73±1.02L and 85.5±13% pred.). HRCTs showed well-defined rounded opacities and enlarged mediastinal lymph-nodes. During follow-up period, wet or automatic finishing was introduced and all workers were supplied with Filtering Face Piece-3 masks. At follow-up, the levels of airborne silica had been drastically reduced (0.009-0.013 mg/m3). We observed a significant decline of TLC (-0.41±0.7L and -6±10% pred., p=0.008), while DLco was stable. A slight increase of HRCT opacities was detected in 6 subjects. No significant relationship between HRCT and TLC worsening was observed. Conclusions: Silicosis due to quartz conglomerates seems characterized by an accelerated lung function decline, despite a reduction of exposure to silica dust. Spirometry appears the most sensitive tool to monitor the progression of the disease.