[Quantitative and qualitative analyses of inorganic dusts in idiopathic interstitial pneumonia (IIP)]

We made quantitative and qualitative analyses of dusts in lung specimens using proton-induced X-ray emission (PIXE) and analytical electron microscopy (AEM). IIP group consisted of 23 patients. Control group, that had no apparent history for dust inhalation, consisted of 21 patients. Control group was matched with IIP group with respects to sex, age, smoking index and life style. For PIXE analysis, the elements Al, Si, P, S, Cl, K, Ca, Ti, Cr, Fe, Co, Ni, Cu, W and Au were examined for this study. Tissue specimen preparation for AEM study was based upon carbon extraction method. The amounts of Al and Si were significantly larger in IIP group than in the control group (Al: IIP 24.40 +/- 19.08 ng/60.8 mm2 and control 11.90 +/- 8.66, P less than 0.01; Si: IIP 54.43 +/- 45.18 and control 28.72 +/- 15.56, P less than 0.05). The elements Co, W and Au were not detected. The amounts of Si correlated inversely with PaO2 (r = -0.454, P less than 0.05). AEM study demonstrated larger amounts of free silica and silicate in IIP group than in the control group (free silica: IIP 0.7% and control 0.2%, P less than 0.01; silicate: IIP 2.6% and control 0.8%, P less than 0.01). These results suggest that inhalation of Si, especially of free silica, may have etiologic significance in IIP.