Welcome to Out of the Loop!

The date is November 21st, 2016. A blustering thunderstorm has just passed through Melbourne, and all at once, thousands of Victorians are finding it difficult to breathe.

In the 24 hours that followed, a wave of almost 500 asthma-related hospital admissions overwhelmed the city’s hospitals and ambulances. 72% had never had asthma before. Ten people died.

What happened is known as a thunderstorm asthma event. While the 2016 epidemic was the largest to date, similar events have been reported across Australian since 1987. But what is it about thunderstorms that raises the risk of asthma so drastically? And how can it affect people without any history of the disease?

Let’s start with some anatomy and meteorology.

The upper respiratory tract is well-equipped to filter out foreign airborne particles. Typically, anything larger than 10 microns gets lodged in the nose and throat, rather than making its way down to the lung tissue. This includes grass pollen, which is usually 30 to 50 microns. If you have hay fever, this is why you’ll get an itchy throat or runny nose, but it will rarely affect your breathing.

But just before a thunderstorm, strong winds and moist air can disrupt the structural integrity of the pollen grains, sheering them into particles as small as 2.5 microns – small enough to reach the lungs. If you’re already sensitive to pollen, this puts you at high risk of having your first ever asthma attack.

Other factors can exacerbate the situation further. Storm winds can carry pollen from regional farmlands all the way to population centres and create an extremely high pollen count. Sudden temperature drops can also trap cool, pollen-filled air at ground level.

If these circumstances align and are severe enough, they might just be enough to cause a thunderstorm asthma event.

Thunderstorm asthma is managed just like any other asthma attack, but the biggest public health risk comes from its potential to affect people with no prior history of asthma, with no medication or asthma management plan. So, with the beginning of the pollen season, make sure to keep an eye on the pollen count, and your antihistamines and inhalers handy!

By Daniel Bil
Brand/IT Officer, AMSA Global Health 2019
[email protected]