Background: Grass pollen is the world’s most harmful outdoor aeroallergen, yet it is not known how airborne assemblages change in time and space. Human sensitivity towards grass pollen varies between species, of which there are over 150 in the UK that flower at different times across the allergy season. However, due to few unique morphological features, grass pollen of different genera cannot be discriminated using traditional observational methods. Currently there is no way of detecting, modelling, or forecasting the atmospheric dispersion of pollen from the biodiversity of grasses, and it is unknown if temporal turnover in species composition match terrestrial flowering or if species richness steadily accumulates over the grass pollen season. Using two complementary DNA barcode markers (rbcL and ITS2), we aim to identify how the taxonomic composition of grass pollen exposure changes across the temperate grass allergy season. Results: Here we show that all grass genera display discrete, temporally restricted peaks of incidence which vary with latitude and
longitude across Britain. We reveal that the taxonomic composition of airborne grass pollen changes substantially across the grass allergy season, and changes in total grass pollen concentration, measured using traditional observational methods, are the result of many grassspecies and not a single flowering species of grass. We also demonstrate that local flowering events, with appropriate temporal delays, may be useful for predicting the incidence of particular species of grass pollen in the air. Significance: Our results demonstrate how targeted, high-throughput sequencing can be used to understand the biodiversity of airborne pollen communities and fill a substantial knowledge gap that has persisted over the past 50 years of aerobiology
research. By developing more refined aeroallergen profiling, we anticipate that our findings will facilitate the exploration of links between taxon-specific exposure of harmful grass pollen and disease, with concomitant socio-economic benefits.