A method of direct particle deposition on a carbon planchet to study mineral dust in human lung by scanning electron microscopy

Abstract

Following Na-hypochlorite digestion of lung tissue, mineral particles extracted in the chloroform layer were deposited directly on a presmoothed carbon planchet for combined scanning electron microscopy and Xray energy dispersive spectrometry (SEM and XEDS). Total mineral particle counts were obtained, and detailed physical characteristics of the fibrous particles were documented at 600, 1,500, 4,500, and 9 , 0 0 0~ in three lungs without, and one lung with, histories of occupational exposure. This preparation method was simple, collected more than 99% of identifiable mineral particles in the chloroform layer, gave excellent object to background contrast without heavy metal coatings, and was suitable for XEDS. Comparable fibrous particles from the chloroform layer could also be studied by selected-area electron diffraction to complement the results of XEDS. By this method, we found particles or fibers larger than 0.1 pm were readily counted and measured at 4 , 5 0 0~. At ~O O X , ferruginous bodies were found to be more than twice in number than when sought €or by Iight microscopy. It was determined that 4,500~ is the most efficient magnification to examine and diagnose this type of specimen. The present study illustrates the importance of determining the most efficient magnification to be utilized in particle counts.