Indoor airborne fungal levels in selected comprehensive compartments of the Urban Utility Tunnel in Nanjing, Southeast China

Abstract The aims of this work were to quantitatively and qualitatively study airborne fungi in three typical and representative comprehensive compartments of a utility tunnel in Nanjing. The concentration and composition of airborne fungi were investigated with a six-stage impact air microbe sampler and by combining culture and DNA analysis. In the three studied comprehensive compartments, the highest concentration of fungi was found at the endpoint of JDS Road (931 CFU/m 3 ), followed by the intersection (895 CFU/m 3 ) and the middle (729 CFU/m 3 ). The fungal levels of all three compartments exceeded the WHO threshold value and thresholds of other countries (500 CFU/m 3 ). Among the identified fungal species, Ascomycota (81%) were ubiquitous at the phylum level. At the genus level, pathogenic fungi Aspergillus (39%) were the most numerous, and other pathogenic fungi included Cladosporium (15%), Alternaria (4%) and Penicillium (2%). Considering the size distribution, Aspergillus and Penicillium were detected primarily in stage IV (2.1˜3.3 μm) and stage V (1.1˜2.1 μm). Cladosporium showed the highest collection rate in stage IV (2.1˜3.3 μm). Ventilation of the compartment reduced the concentration of total fungi by 29%. This study is of interest as there are limited reported researches on the fungal air quality in utility tunnels.