The environment and our health

On 21 November 2016, Melbourne experienced a catastrophic thunderstorm asthma event.

  • 12,723 patients presented at emergency departments across Victoria – 44% more than usual.

  • Emergency departments saw a 672% increase in respiratory-related presentations within a 30-hour period.

  • 3841 more people than usual were admitted to hospital for respiratory distress and asthma.

As a result of the thunderstorm, 10 people died.

A study in the medical journal The Lancet suggests the likely cause of the event was a combination of environmental factors such as:

  • a north-south line of thunderstorms that swept eastwards.

  • a front of wind gusts.

  • a sudden drop in temperature.

  • a sudden increase in humidity.

  • extremely high levels of airborne grass pollen.

A deadly combination

Thunderstorm asthma occurs when a large number of people develop asthma symptoms over a short period of time because of high amounts of grass pollen and a certain type of thunderstorm.

In the Melbourne thunderstorm asthma event, there was a very high concentration of ryegrass pollen in the air. The rain and moisture in the air ruptured the pollen grains, releasing starch granules. Instead of staying high in the air as they normally would, the airflow from the thunderstorm brought the granules to land, which meant they could enter people’s lungs as they breathed.

Could it happen again?

Extremely high levels of airborne ryegrass pollens are reasonably rare in Melbourne, and vary from year to year. However, the Lancet study suggests that climate change might mean extended pollen seasons and an increasing likelihood of extreme weather events such as thunderstorms.

What to do to prevent and manage thunderstorm asthma

Asthma Australia recommends preventative and management measures including:

  • Discussing the risk and possibility of thunderstorm asthma with your doctor.

  • Having an asthma management plan.

  • If you have asthma, avoid allergens around times of high pollen by staying indoors with no open windows.

  • Following asthma management plan including taking preventer medications.

Thunderstorm asthma facts

Thunderstorm asthma is triggered by a combination of high pollen and a certain type of thunderstorm.

Those affected do not necessarily have a history of asthma, but people with asthma and hay fever are most at risk.

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