Airborne fungi in four stations of the St. Petersburg Underground railway system

The fungal and bacterial aerobiota of four St. Petersburg Underground stations has been examined over a 4-month period. In the indoor air of St. Petersburg Underground 50 fungal species were found, among which were likely deteriogenic fungi. The most prevailing genera were Acremonium, Aspergillus, Cladosporium and Penicillium. Fungal spore density in the underground air was within the sanitary level accepted for public buildings. The spore densities and specificities correlated with the station type. A more specific (independent of outdoor) air mycobiota was found in deeper stations. All fungal isolates were tested in laboratory conditions for their ability to produce extracellular proteinase, phospholipase, and hemolytic activities which can be associated to virulence. Only 2 of the 75 isolates expressed a high level of all three activities. Assuming this figure can serve as a rough assessment of pathogenicity potential, the risk of invasive mycoses was not considered significant. But taking into account the situation with peak-hours overcrowding, it may be concluded that the risk of “mould” allergic diseases for some categories of the underground passengers in St. Petersburg does exist.