Assessing population exposure to airborne fungi in the UK over one year using high-throughput sequencing (HTS) metabarcoding methods

Airborne fungi are significant contributors to allergic and infectious disease. While microscopy remains the primary method for fungal identification, high-throughput sequencing (HTS) enables untargeted analysis of a much wider range of environmental taxa. This study used HTS to better characterise airborne fungal composition over a 12-month period in two UK locations, the city of Leicester in central England and a rural site in Chilton (Oxfordshire) approximately 115 km further south. Air samples were collected over a year. A subset of 240 samples (120 per location) were analysed by HTS with a combined internal transcribed spacer region (ITS2) and D1/D2 region of the large subunit (LSU) metabarcoding approach. With statistical imputation a representative 12-month dataset was created. Differences in fungal diversity and composition were explored, incorporating meteorological data. HTS analysis identified 272 fungal genera across locations and seasons, approximately 4-fold more than in other studies using traditional microscopy methods. Fungal diversity, richness and composition at the two locations were broadly similar with some taxa-specific differences likely reflecting land-use types (urban vs rural) and/or local meteorological variables. In particular, air temperature and precipitation significantly influenced fungal composition. This study demonstrates the value of HTS for characterising airborne fungi. While it does not provide absolute quantitation, HTS could be used as a screening tool to identify novel associations between fungal exposure and health outcomes, and should be used in combination with quantitative methods, such as microscopy and quantitative PCR (qPCR). Greater spatial and temporal understanding of the wide range of airborne fungal exposure is crucial for exploring associated health impacts and developing improved public health interventions and alert systems for susceptible individuals.