Scanning Microscopy


Bronchoalveolar lavage (BAL) is a simple and non-invasive sampling technique of the deep lung. Analytical electron microscopy was used for the identification and quantification of non-fibrous inorganic particles recovered in BAL fluid samples from 51 subjects with various occupational exposures (silica, silicates, metals and alloys, metallic oxides, precious and hard metals, abrasives). Around 4750 particles were analysed. More than sixty different compounds were identified, among which silica, kaolinite, illite, mica, Fe oxides and hydroxides, appeared to be ubiquitous. Feldspar, talc, chlorite, Al oxide, Ti oxide, tungsten carbide, stainless steel, carbonaceous compounds and flyash were also frequently encountered. From 1 to 21 compounds were identified in each sample. Repeated BAL samples obtained for 2 subjects did not show significant differences. Particles characteristic of the occupational exposure were found in BAL up to 21 years after cessation. BAL content can also reflect mixed occupational exposures. Absolute particle concentrations measured in twelve samples ranged between 0.1 and 9.9 x 106 particles/ml BAL fluid and mean particle diameter ranged between 0.5 and 1.2 μm.

Mineralogical analysis of non-fibrous particles in BAL can be a useful tool to investigate occupational exposures. It allows, in most cases, a better characterization of the exposure than medical questioning. It may be helpful in identifying pathogenic particles, however it must be kept in mind that a positive result is only a proof of exposure and never a proof of disease. The main limitations of this technique are difficulties in sampling severely diseased subjects and inaccuracy in detecting easily soluble compounds and particles with a high rate of alveolar clearance.

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