Hydrometeorological drivers of Cupressaceae pollen rupture in southeastern Spain

The rupture of Cupressaceae pollen grains significantly affects allergenic exposure and depends on specific hydrometeorological factors. This study analysed the main meteorological variables influencing pollen rupture in three cities in southeastern Spain during two pollen seasons (2019-2020 and 2020-2021). Using data from the Aerobiological Network of the Region of Murcia and standardised sampling methods (EN 16868), the study quantified total pollen concentrations, disrupted pollen (DP) levels and percentage of disrupted pollen (DPP).

The results reveal that the main factors influencing pollen rupture are related to water, specifically relative humidity and precipitation. Higher relative humidity levels were positively correlated with increased DP and DPP, indicating that relative humidity triggers structural changes in pollen grains. Precipitation showed a dual effect, simultaneously promoting pollen swelling and disruption while reducing airborne concentrations due to its wash-out effect. The influence of relative humidity aligns with the reproductive mechanisms of Cupressaceae, which rely on hydration for pollen tube formation. The percentage of disrupted pollen was significantly higher during periods of high relative humidity, with always positive correlations.

Statistical analyses confirmed that geographical characteristics and bioclimatic indices had a limited influence compared to localised factors such as urban ornamental flora and specific hydrometeorological conditions. Differences between the cities studied were also explored using hierarchical clustering dendrograms. These visualisations highlighted different clustering patterns based on pollen concentration and meteorological variables, highlighting the importance of localised urban vegetation management in influencing allergenic risks.

The results showed the dual role of precipitation in influencing airborne allergen exposure. This duality highlights the importance of considering both weather conditions and urban planning strategies to mitigate health risks. Management of ornamental Cupressaceae in urban areas, combined with monitoring of high relative humidity periods, could significantly reduce allergen exposure.

The integration of aerobiological and meteorological data networks provides a robust framework for allergen risk forecasting. Such systems can provide real-time alerts to vulnerable populations, especially during high pollen seasons. A better understanding of factors such as relative humidity and rainfall will improve public health responses and inform sustainable urban development policies.