Mould in buildings: the air spora of domestic dwellings

Filamentous fungi in 37 genera were isolated during winter from the internal air of 62 domestic dwellings in England and Scotland. In the air spora the number of viable fungal colony-forming units (cfu), including yeasts, ranged from < 12 to 449 800 cfu m⁻³. There was considerable variation between dwellings and between weekly samples taken within the same dwelling, but in approximately one-third of all air samples there were < 200 cfu m⁻³. The filamentous fungi isolated most frequently from the air in 47 Scottish dwellings were Penicillium spp. (96% of dwellings), Cladosporium spp. (89%), Aspergillus spp. (75%, mainly A. versicolor), Ulocladium spp. (62%), Geomyces pannorum (57%) and Sistotrema brinkmannii (51%). Yeasts were isolated in 94% of these dwellings and overall comprised 13% of cfu on Andersen sampler plates. Penicillium spp., Cladosporium spp. and S. brinkmannii together accounted for > 70% of the propagules. High numbers of spores in the internal air were associated with surface mould growth and constructional work. In addition, disturbance of surface growth and vacuum cleaning of carpets caused large temporary increases in the atmospheric spore count.