Analysis of inorganic fiber concentrations in biological samples by scanning electron microscopy

Analyzing fibers with electron microscopic techniques involves several preparation steps, especially during the analysis of fibers in human tissue. The influence of these steps on the analytical result was studied in detail. Fiber number was unaffected by the mild sonication of fiber suspensions analyzed with scanning electron microscopy. Significant fiber losses appeared during the filtration of fiber suspensions through 0.8-micrometer pore-size Nuclepore membranes. Shrinkage of the tissue during dry ashing broke lung fibers and consequently increased the fiber concentration and affected the fiber length distribution. Dry ashing, however, removed more of the organic debris than wet ashing; thus specimens prepared with dry ashing were more suitable for scanning electron microscopic analysis. A fairy good correlation was demonstrated for the analysis of fibers with scanning and transmission electron microscopy.