Thunderstorm asthma, the unexpected impact of lightning storms on pollen allergies

Thunderstorm asthma, the unexpected impact of lightning storms on pollen allergies

Source: Geolog (European Geosciences Union)

Image credit: Michiel Baatsen, (distributed via imaggeo)

In October 2015 a series of massive thunderstorms rolled across the Eastern Mediterranean. In the hours and days that followed many people living along the Israeli coast had to go to their nearest medical centre because they were experiencing respiratory problems, which appeared very similar to asthma. But what could have caused these breathing problems? Well in research recently published in Natural Hazards and Earth System Sciences, Yoav Yair and their co-authors reveal that these people were probably suffering from thunderstorm asthma.

Thunderstorm asthma is a rare condition, where a severe thunderstorm can increase the number of airborne particles, including pollen and pollution. In the case of the pollens, the high humidity and pressure of very large thunderstorms can cause the pollen grains to break apart, releasing the allergens to the atmosphere in much higher concentrations than normal. These allergens are then forced back down to the ground level in powerful downdrafts. In desert areas, these downdrafts are often very visible as they also collect dust and other tiny particles to form dust walls or ‘haboobs’ that travel out ahead of the storm.

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If the thunderstorm happens during a time of year when there is pollen in the air anyway (usually in the spring or summer) the massive increase in pollen-based allergens can cause thunderstorm asthma. Grass pollens are particularly bad offenders here, as the pollens are too large to cause severe allergic reactions normally (usually resulting in milder symptoms like hayfever) but the combination of heavy rainfall AND the pressure and humidity of the storm causes the pollen grains to break apart and release a major allergen. In addition to the allergic reactions caused by the pollen fragments, the lightning itself could make the problem worse, as intense lightning creates atmospheric oxides like ozone. You may recognise these atmospheric oxides as the sizzling smell you can sometimes detect when a lightning storm is nearby. In large enough amounts, ozone can also cause respiratory problems, which just adds to the issues faced by people who are sensitive to these conditions.

A schematic description of the mechanism that enhances the concentrations of airborne
aerosols (either pollution particles or pollen) ahead of a mature thunderstorm (Taylor and
Jonsson, 2004). 

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