Hygroscopicity of fungal spores

Aerodynamic size and hygroscopicity of fungal spores have been studied experimentally using non-aggregated spore aerosols of five different species. The results show that fungal spores are only slightly hygroscopic. The highest hygroscopic change in particle size was found with Cladosporium cladosporioides: its aerodynamic diameter increased from 1.8 mu m to 2.3 mu m when the relative humidity increased from 30% to similar to 100%. Our numerical assessment shows that this particle size change results in 20-30% increase of respiratory deposition of spores.