Detection of silica particles in lung tissue by polarizing light microscopy.

The detectability of silica particles in ordinary histologic sections by means of polarizing light microscopy has been controversial. Through the application of both correlative light microscopy and scanning electron microscopy to different lung sections, we showed that particles demonstrating peaks for silicon only by energy-dispersive x-ray microanalysis were in fact visible by polarizing light microscopy. These particles included some silica particles less than 1 microns in diameter. We found no correlation between the intensity level of the light source used for polarization and the differential ease of visualizing silica versus silicates; examples of both could be detected at both relatively low and high light intensities. This suggests that geometric parameters may be as important as composition in the ease of detection of silica versus silicates with polarized light.