Temporal/seasonal variations of size-dependent airborne fungi indoor/outdoor relationships for a wind-induced naturally ventilated airspace

With the use of published temporal/seasonal size characteristics of fungal spores and meteorological data in the subtropical climate, we estimated the airborne fungal concentration indoor/outdoor (I/O) ratios in a wind-induced naturally ventilated home. We expanded previous size-dependent indoor air quality model based on a hygroscopic growth factor as a function of relative humidity (RH) on aerodynamic diameter and concentration of fungal spores. The average geometric mean diameters of airborne fungi decreased from outdoor 2.58±0.37 to indoor 1.91±0.12μm in summer, whereas decreased from outdoor 2.79±0.32 to indoor 1.73±0.10μm in winter, resulting from the effect of hygroscopicity of airborne fungi. The higher indoor airborne fungal concentrations occurred in early and late afternoon in which median values were 699.29 and 626.20CFUm−3 in summer as well as 138.71 and 99.01CFUm−3 in winter, respectively, at 2 a.m. and 8 p.m. In the absence of indoor sources, summer has higher mean I/O ratios of airborne fungal concentration (0.29 – 0.58) than that in winter (0.12 – 0.16). Parsimoniously, our proposed RH-corrected I/O ratio model could be used to estimate the indoor source concentrations of bioaerosols provided that the actual measured fungus-specific I/O ratios are available.