The composition and concentration of airborne fungal propagules are probably determined by many interrelated environmental factors, such as temperature, relative humidity, atmospheric pressure, wind speed, rainfall and gas pollutants. The importance of these variables was assessed in an outdoor sampling survey conducted at regular intervals for 12 months at a single site in Turin. Samples were collected with a single-stage volumetric sieve sampler on potato dextrose agar supplemented with 15 mg l−1 streptomycin and 50 mg l−1 chloramphenicol.

Canonical Correspondence Analysis showed that the four ordination axes accounted for 93·5% of the variance in relationships between fungal entities present in more than 20% of samples and the environmental variables. The Monte Carlo permutation test demonstrated that the ordination was highly significant (P=0·01). The community's qualitative and quantitative composition mainly depended on the factors that have the greatest influence on Turin's climate, i.e., in descending order, temperature, relative humidity and rainfall. The relative importance of these environmental variables on different groups of fungi was assessed. Wind speed positively correlated with the fungi producing conidia of larger sizes.