healthHealth and Medicine

We Now Know What Causes Deadly "Thunderstorm Asthma" Outbreaks


Robin Andrews

Science & Policy Writer

It's all about the tiny pollen. Dmytro Balkhovitin/Shutterstock

Every now and then, during a significant thunderstorm, those suffering from asthma can experience severe attacks – and the consequences can sometimes be fatal. Known appropriately as “thunderstorm asthma,” one of the most extreme examples of this on record took place last October in Melbourne, Australia, where 8,500 people were admitted to hospital and six of them died.

Although theories have cropped up as to why the two phenomena are linked for more than three decades now, a new study by a team led by Australia’s University of Georgia (UGA) has conclusively defined the triggering mechanisms.


Writing in the Journal of Applied Meteorology and Climatology, they have found that the high winds, the electrical discharge, the high humidity, and tiny grass pollen particles all play starring roles as antagonists.

Based primarily on the Australian event, they explain that it all starts with bioaerosols, particles released from various ecosystems that are mixtures of organic and inorganic components. Pollen, mold spores, and dust are frequently found within these floating blobs.

The high humidity and rainfall that comes with particularly bad thunderstorms break open these levitating conglomerates, which scatters the pollen and dust into the air in millions of little explosions.

The high electrical discharge that accompanies thunderstorms exacerbates this fragmentation and, combined with strong downdraft winds, ensures that it is blown into the faces of anyone miles down the road from the storm itself.


“While this study does not yet provide the capability of predicting thunderstorm asthma outbreaks, our methodology may provide a key piece to the puzzle for alerting public health officials about what storms may trigger an episode and which ones may not,” co-author Marshall Shepherd, a professor of geography and atmospheric sciences at UGA, said in a statement.

Either way, it’s now clear that the combination of the above characteristics represents the “perfect storm” of conditions that will trigger severe asthmatic symptoms in enormous groups of people. Some have described them as asthma “epidemics.”

Incredibly, the Melbourne event was so potent that it essentially gave asthma to those that never had it. Of the thousands afflicted that day, up to 40 percent had never experienced asthmatic symptoms prior to that date. This is thought to be because rye grass pollen was involved, which is so small that can easily infiltrate and inflame our airways.

Certain pollen makes things worse than others. Juergen Faelchle/Shutterstock


Some researchers suspect that anthropogenic climate change is actually making things worse. Experiments show that increasing concentrations of atmospheric carbon dioxide appear to increase the amount of pollen certain plants give off.

Ultimately, this means that thunderstorm asthma is perhaps more prevalent today than it ever has been through human history – and it’s set to get worse as time ticks on.


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