Energy-dispersive X-ray analysis and scanning electron microscopy of pleura. Study of reference, exposed non-pneumoconiotic, and silicotic populations

Some pleural effusions labeled as idiopathic could be produced by the inhalation of silica

Objectives

Exposure to silica nanoparticles has been associated with pleural effusions (PEs) in animal models and case series. We hypothesized that some PEs labelled as “idiopathic” could, in fact, be secondary to inhalation of silica.

Methods

A retrospective case control study was designed utilizing a prospectively maintained pleural database. Cases, represented by idiopathic PEs, were matched by age and gender to control patients who had been diagnosed with malignant, cardiac, or infectious PEs. A survey consisting of questions about occupational life and possibility of silica inhalation was conducted. In a subgroup of patients, pleural fluid concentrations of silica were quantified by plasma atomic emission spectrometry analysis. Also, the pleural biopsy of a silica-exposed case was subjected to an energy dispersive X-ray spectroscopy (EDX) to identify the mineral, the size of which was determined by electron microscopy.

Results

A total of 118 patients (59 cases and 59 controls) completed the survey. There were 25 (42%, 95% CI 31–55%) and 13 (22%, 95% CI 13–34%) silica-exposed workers in case and control groups, respectively. The exposure attributable fraction was 0.62 (95% CI 0.14–0.83). Four of eight exposed cases showed detectable levels of silica in the pleural fluid (mean 2.37 mg/L), as compared to none of 16 tested controls. Silica nanoparticles of 6–7 nm were identified in the pleural biopsy of an exposed case patient.

Conclusions

It is plausible that some idiopathic PEs could actually be caused by occupational silica inhalation.

Silicosis-related pleural effusion diagnosed using elemental analysis of the pleural fluid cell block: A case report

Pleural disease in silicosis remains an underrecognized entity. Herein, we describe the case of an 85-year-old man with a 20-year history of silica exposure between the ages of 9–28 years. He presented with bilateral exudative pleural effusions, and chest computed tomography revealed typical silicosis findings. Thoracentesis was performed thrice, but did not reveal the cause of effusion. However, pleural fluid cell-block elemental analysis revealed a silicon compound, suggesting that silicosis-related pleural effusion had developed after a long latency period. Therefore, elemental analysis of the pleural fluid cell block may help diagnose occupational lung diseases with pleural effusion.

Mechanistically identified suitable biomarkers of exposure, effect, and susceptibility for silicosis and coal-worker's pneumoconiosis: a comprehensive review

Clinical detection of silicosis is currently dependent on radiological and lung function abnormalities, both late manifestations of disease. Markers of prediction and early detection of pneumoconiosis are imperative for the implementation of timely intervention strategies. Understanding the underlying mechanisms of the etiology of coal workers pneumoconiosis (CWP) and silicosis was essential in proposing numerous biomarkers that have been evaluated to assess effects following exposure to crystalline silica and/or coal mine dust. Human validation studies have substantiated some of these proposed biomarkers and argued in favor of their use as biomarkers for crystalline silica- and CWP-induced pneumoconiosis. A number of "ideal" biological markers of effect were identified, namely, Clara cell protein-16 (CC16) (serum), tumor necrosis factor-alpha (TNF-alpha) (monocyte release), interleukin-8 (IL-8) (monocyte release), reactive oxygen species (ROS) measurement by chemiluminescence (neutrophil release), 8-isoprostanes (serum), total antioxidant levels measured by total equivalent antioxidant capacity (TEAC), glutathione, glutathione peroxidase activity, glutathione S-transferase activity, and platelet-derived growth factor (PDGF) (serum). TNF-alpha polymorphism (blood cellular DNA) was identified as a biomarker of susceptibility. Further studies are planned to test the validity and feasibility of these biomarkers to detect either high exposure to crystalline silica and early silicosis or susceptibility to silicosis in gold miners in South Africa.

Silica-induced pleural disease: an unusual case mimicking malignant mesothelioma

A 57-year-old man with a history of exposure to silica for 32 years presented with pleural thickening of the lower lobe of the left lung and a chronic right-sided pleural effusion without any radiographic evidence of parenchymal nodules in either lung. Light microscopic examination of a left visceral pleural biopsy specimen revealed markedly thickened pleura with fibrosis and macrophages containing birefringent silica and silicates. Occasional rounded intrapleural silicotic nodules were present. The underlying lung tissue did not show fibrosis or silicotic nodules. An energy-dispersive x-ray analysis confirmed the presence of silica. In the absence of lung involvement, this case represents a very unusual pathologic reaction caused by silica and silicates and adds to the clinical differential diagnosis of chronic pleuritis and malignant mesothelioma.