Effects of electric fields on pollen rupture

RATIONALE: To determine whether the potential for previous termpollennext term fragmentation is increased during thunderstorms by exploring the previous termeffectsnext term of previous termelectricnext termprevious termfieldsnext term, with magnitude as found in the outdoor environment.

METHODS: Fresh previous termpollennext term grains were collected from bermudagrass flowers. A light microscope was modified with the addition of an previous termelectricnext termprevious termfieldnext term generated from a DC source (0-20 V) that was applied to the stage. Water was added to test for previous termpollennext termprevious termrupturenext term and to assess previous termpollennext term viability.

RESULTS: Bermuda grass previous termpollennext term did not previous termrupturenext term within 1 h of contact with water. Only after exposure to an previous termelectricnext termprevious termfieldnext term did Bermudagrass previous termpollennext term show a considerable amount of rupturing immediately upon immersion in water. The higher the voltage the previous termpollennext term is exposed to before coming into contact with water, the higher the percentage of previous termrupturenext term of the previous termpollennext term. previous termElectricnext termprevious termfieldsnext term, generated in the laboratory and of magnitude found during thunderstorms, affected the previous termpollennext term after as little as a 5 s exposure. The highest percentage of previous termrupturenext term occurred after exposures of at least 10 s: 80% previous termrupturenext term occurred after 10 s exposure at 10kVolts/m. This previous termeffectnext term is sustained for at least 15 min.

CONCLUSIONS: Thunderstorm regularly generate previous termelectricnext termprevious termfieldsnext term up to 5 kV/m in strength, and can reach 10kV/m, and cover several km in distance. The magnitude of the previous termelectricnext termprevious termfieldsnext term that affects the previous termpollennext term grains in the laboratory is low enough to be commonly found in the outdoor environment during thunderstorms. These previous termelectricnext termprevious termfields prime previous termpollen grains for more rapid release of allergenic particles.

Release of allergens in respirable aerosols : a link between grass pollen and asthma

Background: Asthma incidence has long been linked to pollen, even though pollen grains are too large to penetrate into the airways where asthmatic responses originate. Pollen allergens found in small, respirable particles have been implicated in a number of asthma epidemics, particularly ones following rainfall or thunderstorms.

Objective: The aim of this study was to determine how pollen allergens form the respirable aerosols necessary for triggering asthma.

Methods: Flowering grasses were humidified and then dried in a controlled-environment chamber connected to a cascade impactor and an aerosol particle counter. Particles shed from the flowers were analyzed with high-resolution microscopy and immunolabeled with rabbit anti-Phl p 1 antibody, which is specific for group 1 pollen allergens.

Results: Contrary to what has been reported in other published accounts, most of the pollen in this investigation remained on the open anthers of wind pollinated plants unless disturbed—eg, by wind. Increasing humidity caused anthers to close. After a cycle of wetting and drying followed by wind disturbance, grasses flowering within a chamber produced an aerosol of particles that were collected in a cascade impactor. These particles consisted of fragmented pollen cytoplasm in the size range 0.12 to 4.67 μm; they were loaded with group 1 allergens.

Conclusion: Here we provide the first direct observations of the release of grass pollen allergens as respirable aerosols. They can emanate directly from the flower after a moisture-drying cycle. This could explain asthmatic responses associated with grass pollination, particularly after moist weather conditions.

Thunderstorm asthma

Thunderstorms have often been linked to epidemics of asthma, especially during the grass flowering season; however, the precise mechanisms explaining this phenomenon are unknown. Evidence of high respirable allergen loadings in the air associated with specific meteorologic events combined with an analysis of pollen physiology suggests that rupture of airborne pollen can occur. Strong downdrafts and dry, cold outflows distinguish thunderstorm rain from frontal rain. The weather system of a mature thunderstorm likely entrains grass pollen into the cloud base, where pollen rupture would be enhanced, then transports the respirablesized fragments of pollen debris to ground level where outflows distribute them ahead of the rain. The conditions occurring at the onset of a thunderstorm might expose susceptible people to a rapid increase in concentrations of pollen allergens in the air that can readily deposit in the lower airways and initiate asthmatic reactions.