Across the globe, thunderstorm associated asthma epidemics have been documented by a peak in hospital admissions for respiratory symptoms where there is both a high level of airborne pollens and thunderstorm activity.
The most severe event in Australia occurred in Melbourne in 2016.
Grass pollens, dust and other allergens are blown ahead of the storm-front by the outflow of air, as seen in the diagram below (Asthma Australia).
Problems with pollen are usually caused by grasses, weeds, and trees which are wind-pollinated. Australian native plants are usually less of an issue, although there are a few exceptions such as the Cypress Pine and Australian Oak.
These pollens are swept up into the storm front and many are ruptured either by osmotic shock (moisture causing swelling) or by electrostatic effects of lightning. This pollen rupturing creates particles small enough to be breathed deep into the smaller airways within the lungs. Here, they can irritate the lining to cause inflammation, smooth muscle contraction in the airway wall and mucus production all of which obstruct airflow, known as asthma.
Whilst thunderstorm associated asthma epidemics have been reported in both metropolitan and rural areas, the greatest problem is attributed to high grass pollen levels which covers much of rural NSW. In the Riverina, rye grass has been identified as the major culprit associated with the thunderstorm asthma season from September through to December.
High pollen counts during the spring thunderstorm season are not the only trigger for asthma, but these conditions can trigger a severe response. Unfortunately, the onset of symptoms can be quite rapid, making the prompt administration of a reliever medication so important.