Characterisation of exposure to airborne fungi: measurement of ergosterol.

In order to gain a clearer understanding of the level of fungal air contamination in indoor environments, we have adapted and tested a method to evaluate fungal biomass. Liquid phase chromatography (HPLC) of ergosterol, a component of the cell membrane of microscopic fungi, was employed. This method permits the detection and identification of ergosterol molecules at a concentration of 40 microg/ml (n=33, sigma=5). By combining this assay with a rotating cup collection apparatus, it was possible to measure fungal flora levels with a limit of quantification of 0.4 ng/m3 or a theoretical value of 150 spores per cubic meter (m3). Measurements of ergosterol levels performed on different sites showed that this method reflected the different situations of exposure of occupants to airborne fungal flora.

Fungal fragments as indoor air biocontaminants.

The aerosolization process of fungal propagules of three species (Aspergillus versicolor, Penicillium melinii, and Cladosporium cladosporioides) was studied by using a newly designed and constructed aerosolization chamber. We discovered that fungal fragments are aerosolized simultaneously with spores from contaminated agar and ceiling tile surfaces. Concentration measurements with an optical particle counter showed that the fragments are released in higher numbers (up to 320 times) than the spores. The release of fungal propagules varied depending on the fungal species, the air velocity above the contaminated surface, and the texture and vibration of the contaminated material. In contrast to spores, the release of fragments from smooth surfaces was not affected by air velocity, indicating a different release mechanism. Correlation analysis showed that the number of released fragments cannot be predicted on the basis of the number of spores. Enzyme-linked immunosorbent assays with monoclonal antibodies produced against Aspergillus and Penicillium fungal species showed that fragments and spores share common antigens, which not only confirmed the fungal origin of the fragments but also established their potential biological relevance. The considerable immunological reactivity, the high number, and the small particle size of the fungal fragments may contribute to human health effects that have been detected in buildings with mold problems but had no scientific explanation until now. This study suggests that future fungal spore investigations in buildings with mold problems should include the quantitation of fungal fragments.