Airborne pollen concentrations in and around Ingolstadt, Germany: a three-year observational study

Aeroallergens such as pollen and fungal spores can trigger allergic reactions and therefore are of medical and clinical relevance. Allergic diseases are widespread worldwide and affect a large percentage of the population, placing a substantial burden on public health systems. Their prevalence and impact highlight the importance of understanding spatial and temporal variability in aeroallergen exposure. Thus, this study aims to assess spatial and temporal variability in airborne pollen exposure at two sites in and around Ingolstadt, Germany, based on three years of volumetric pollen monitoring.

To enable a direct urban–rural comparison, airborne pollen were monitored over three years (2019–2021) at two nearby study sites in Ingolstadt, Germany: an urban site in the city center (WFI) and a more rural site in the surrounding area (RSK) at a distance of approximately 8 km. Samplers (7-day volumetric traps) were mounted on rooftops to capture daily and bihourly pollen concentrations. We analyzed daily data to identify the most abundant pollen types, and quantified the duration of the pollen seasons, peak days and peak values, and the Seasonal Pollen Integral (SPIn).

Across all years and both sites, the dominant pollen types were Betula, Pinus, Taxus, Urticaceae, and Poaceae. Betula contributed up to one-third of airborne pollen to the pollen load. Among herbaceous taxa, Urticaceae was consistently most abundant, accounting for up to 37% of the annual total. Peak daily mean Betula concentrations at both sites occurred in 2020, reaching 2,378 pollen grains/m³ (WFI) and 2,788 pollen grains/m³ (RSK). We observed substantial differences in Poaceae pollen concentrations between the urban and more rural site across all study years. For example, in 2019 the peak concentration at the more rural site was eight times higher than at the urban site (371 vs. 46 pollen grains/m³). The longest pollen seasons were observed for Picea and Brassicaceae: at WFI, 251 (2021) and 185 (2019) days, respectively; at RSK, 173 (2021) and 178 (2019) days, respectively.

Despite the short distance between the two sites, clear urban-rural differences in pollen exposure were observed, pointing to the importance of land use and other local environmental conditions. Extending the monitoring period in future studies will be essential to assess the robustness of these patterns and their variability over time.