Environmental exposure to Aspergillus fumigatus allergen (Asp f I)

Asp f I is a major allergen produced by the mycelia of Aspergillus fumigatus. It is not present in spores and can be used as a specific marker for the detection of germination of this fungus. We investigated the domestic and outdoor concentration of Asp f I in Poole, U.K. and Charlottesville, VA, U.S.A. Asp f I was undetectable in 95% (281/296) of house dust extracts and present at low levels (< 0.17 micrograms/g of sieved dust, mean 0.038 micrograms/g) in the remainder. In contrast, Asp fI could be detected in 65% (15/23) of cultures of house dust, suggesting the presence of viable, but ungerminated, A. fumigatus in the majority of homes. Asp f I was detectable in 80% (28/35) of extracts of leaves and compost, but present in these outdoor samples at low levels (< 0.11 micrograms/g, mean 0.27 micrograms/g). Air sampling for Asp f I was undertaken before and after vigorous disturbances at indoor (n = 5) and outdoor (n = 6) sites. Airborne Asp f I was not detected in domestic samples or in undisturbed outdoor samples. Following disturbance it could be measured in outdoor samples (range 7.6-29 ng/m3). The results suggest that while exposure to A. fumigatus is common, exposure to Asp f I and germinating A. fumigatus is uncommon. It is probable that those individuals who develop antibody responses to Asp f I have been exposed to A. fumigatus which has germinated in their respiratory tract.