The urban mycobiome of transport environments: Characterising the fungal composition of passive dust samples collected in railway stations in England

Fungal bioaerosols, including spores and fragments, are significant components of urban air and are associated with infectious and allergic disease. Despite their importance, fungal bioaerosols are less well studied compared to bacteria and viruses. Mass transit environments, such as railway stations, represent a potential source of occupational and community exposure to fungal bioaerosols. While some studies have analysed the fungal composition of subway systems, there is limited information on overground stations. Here we combined metabarcoding of the ITS2 region with ecological guild assignment to analyse a subset of 259 settled dust samples collected from 9 stations across England over a 12-month period. These samples were part of a larger set of 1287 samples collected from 17 English and Scottish overground railway stations that had been previously analysed with traditional culture methods. Our approach enabled the identification of a wider range of fungal taxa than the original study, demonstrating that the urban mycobiome of the railway stations was a dynamic balance of taxa from both environmental and human sources covering diverse functional guilds. Station location, layout and season independently contributed to urban fungal richness, diversity, and composition. Functional guild analysis enabled identification of possible fungal sources and highlighted those of potential concern for workers and commuters. Future research should focus on better understanding source apportionment, the biological mechanisms linking fungal exposures to adverse health outcomes and, developing and evaluating targeted interventions to improve air quality within railway stations and other urban public spaces to minimise associated health risks.