The use of ergosterol to measure exposure to fungal propagules in indoor air.

This report concerns the development of a method for the measurement of ergosterol in indoor air as a determinant of fungal exposure. Ergosterol was determined in spores of 11 species of Aspergillus, Penicillium, and Cladosporium selected from the most common molds in 400 homes in Ontario. Spore ergosterol content was about 1 microgram/mg, which is the range reported for mycelia, and varied by about 25% for the species tested. Ergosterol was determined in bedroom air samples taken in the winter in homes in southern Ontario. The median ergosterol value corresponded to a total concentration of fungal spores on the order of 10 to 10(2) per m3, in the range for other studies where total and viable propagules were determined by other methods. The sampling of air for ergosterol is a robust method for assessing fungal biomass in air, but provides no information on the species present.