Impact of Atmospheric Charge Regimes (Static Fields and Arcing) on Airborne Tree Pollen Rupture under Dry and Wet Conditions

Thunderstorm asthma events are acute asthma epidemics linked to the release of subpollen particles (SPPs) following pollen rupturing, with atmospheric electric charges speculated to contribute. This research used a novel Environmental Chamber for High Voltage and Oxidative Air Pollutants (ECHO) with Birch, She-oak, and Pine pollen exposed to static electric fields (105-420 kV/m) and impulse arc discharges (760-830 kV) in dry and wet conditions using the TERCO HV9000 system. Results showed species-specific responses, with birch pollen demonstrating a propensity to rupture under static and arcing conditions, as confirmed using aerosol sizers and characterization techniques such as scanning electron microscopy (SEM) and energy X-ray dispersive spectroscopy (EDS). Under wet conditions, birch pollen ruptured, generating substantial submicron particles, reaching 1600-1900 particles/cm³ under static fields and 10,500 particles/cm³ during arcing. She-oak pollen produced SPPs at higher electric potentials (315-420 kV/m), with shifted particle size distribution, whereas pine pollen remained resilient to similar exposure treatments. These findings provide the first experimental evidence that electrical charges can cause pollen rupture independently, with high humidity further increasing rupture propensity. As climate change exacerbates extreme weather events, this study presents crucial evidence on mechanisms of thunderstorm asthma and pollen responses to such conditions.