Airborne fungal colony-forming units in outdoor and indoor environments in Yokohama, Japan.

The fungal concentration and flora in indoor and outdoor air in Yokohama, Japan were analyzed with a Reuter centrifugal air sampler and dichloran 18% glycerol agar (DG18), and compared with the levels assessed with potato dextrose agar (PDA). The number of fungal colony-forming units (CFU) in outdoor air was < 13-2750/m3; Cladosporium spp. predominated, followed by Alternaria spp. and Penicillium spp. The fungal concentration in outdoor air peaked in September. The concentrations of fungi in outdoor air (n = 288) were significantly correlated with the maximum temperature of the day, minimum temperature of the day, average temperature of the day, average velocity of wind of the day, average temperature of the month, average relative humidity of the month and precipitation of the month. In indoor air, the fungal CFU was < 13-3750/m3. Cladosporium spp. predominated, followed by the xerophilic fungi such as the Aspergillus restrictus group, Wallemia sebi, the A. glaucus group, and Penicillium spp. The fungal concentration in indoor air peaked in October. The concentrations of fungi in indoor air (n = 288) were significantly correlated with the indoor temperature, indoor relative humidity and the outdoor climatic factors mentioned above, except for the average velocity of wind of the day.