On November 21st, 2016 a thunderstorm swept across Melbourne, Australia. It brought with it the usual flooded basements, wet shoes and ruined picnics, but it also brought a strange outbreak of asthma. Asthmatics and non-asthmatics alike suddenly found themselves unable to catch their breath, coughing and in extreme cases not being able to breathe at all. By the time the storm had passed, there was a 672% increase in respiratory-related presentations to emergency departments and a 992% increase in asthma-related admissions to hospital. The storm contributed to the death of at least 10 people.
So what was it about this thunderstorm that spurred a city-wide asthma attack? Experts aren’t certain, but the best guess is pollen. It seems that pollen, mould and other allergens can get picked up into a storm, riding on wind currents, and carried into the clouds. Up in the sky, they make contact with water molecules, which causes these allergens to break apart into microscopic particles that can more readily enter human lungs and cause reactions.
In the case of Melbourne, the allergen of importance seems to be from ryegrass. A grain of ryegrass pollen can be broken down into 700 starch granules, measuring 0.6 to 2.5 μm, which may then be inhaled into the deepest parts of the lungs, and cause an asthma attack or an allergic reaction.
As roughly 20% of the world is sensitive to grass or tree pollens, you can imagine that these storms are quite bothersome to many. Melbourne wasn’t the first case of casualties due to storm inflicted asthma, and it sadly will probably not be the last.
