The pollen count is undertaken to prevent another thunderstorm asthma event

GOOD EFFORT: Creswick pollen counters Yasika Medhavi Subasinghe, Yogendra Karna and Nadeeshani Karannagoda. Photo: Dylan Burns
GOOD EFFORT: Creswick pollen counters Yasika Medhavi Subasinghe, Yogendra Karna and Nadeeshani Karannagoda. Photo: Dylan Burns

Three Melbourne University PHD students are contributing to the prevention of another thunderstorm asthma epidemic one pollen count at a time. 

Every morning at 9am, Yasika Medhavi Subasinghe, Yogendra Karna and Nadeeshani Karannagoda climb to the roof of Melbourne University’s Creswick campus to collect a pollen sample. 

Ms Medhavi Subasinghe said she and her colleagues use an air sampling device called a ‘Bukard’ pollen trap, in which sits a sticky slide. 

“It draws in air at a constant speed as it rotates clockwise for 24 hours,” she said. “This collects not only airborne grass pollen, but also dust particles and fungal spores.”

Once the sample has been collected, the students apply a dye to the slide so they can count the pollen under the microscope. 

ROUND: Grass pollen under the microscope. Photo: Melbourne University

ROUND: Grass pollen under the microscope. Photo: Melbourne University

Grass pollen is one of the most significant allergens in Australia. Most of Melbourne’s grass pollen comes from perennial ryegrass pastures to the north and west of the city, while parts of regional Victoria also have high levels of grass pollen due to pastures.

“There are many types of pollen and one of them is grass, which is causing the asthma problem. We count all the pollen but keep a separate count of the grass pollen as well,” Ms Medhavi Subasinghe said.

The students tally up the number of pollen and grass pollen grains per cubic metre of air caught in the trap in the previous 24 hours by 10.15am each morning.  

This tally is then used to forecast pollen levels for the following 24 hours. 

There are many types of pollen and one of them is grass, which is causing the asthma problem. We count all the pollen but keep a separate count of the grass pollen as well.

Yasika Medhavi Subasinghe

The collated data is then entered into the Melbourne Pollen Count and Forecast website, which the Bureau of Meteorology uses to comprise its daily pollen forecasts as well as to forecast warnings about possible thunderstorm asthma events.

Pollen forecasts are dependent on a number of weather conditions, including temperature, rainfall, wind, humidity and grass coverage. Grass pollen is generally higher during the summer months. 

The Victorian grass pollen monitoring season takes place from October 1 through to December 31 and was introduced following 10 deaths during a thunderstorm asthma event in 2016.

The Creswick monitoring station is one of eight statewide stations, chosen to cover the main population centres, while also capturing grass pollen levels from key ‘source’ areas.

The three pollen counters, all international students enjoying their time abroad, have been counting pollen in Creswick for two years and say they are all really enjoying the experience. 

Ms Karannagoda said going up to the rooftop early in the morning could be “crazy at times if it’s very cold or windy” but she always enjoyed getting the sample back in the lab.

“Different types of pollen are all different colours and shapes so observing it under the microscope is really interesting,” she said. 

“Most of the time the combinations of pollen are different from one day to the other, but the types we find here in Creswick are usually the same – pine, cyprus and grass.”

All three counters agreed pine pollen was the most interesting to look at under the microscope as it had a ‘mickey mouse shape’.

MICKEY MOUSE: Pinus pollen under the microscope. Photo: Melbourne University

MICKEY MOUSE: Pinus pollen under the microscope. Photo: Melbourne University

Ms Karannagoda said she enjoyed being able to warn people about a high pollen forecast. 

“If we count a high amount of pollen on a particular day and a thunderstorm is predicted, we are in a position to give a warning so the general public can prepare.”

Ms Medhavi Subasinghe said there were a number of reasons Creswick was chosen as a monitoring site, with one being that it is in Central Victoria: “Urban pollen concentration is often impacted by regional pollen counts so it is important to count both,” she said.

A thunderstorm asthma event is thought to be triggered by a unique combination of high grass pollen levels and a type of thunderstorm. Mr Karna said pine pores could travel as far as four or five kilometres depending on wind speed.

“Sometimes pine pollen can travel four or five kilometres but grass pollen can’t travel long distance because it is smaller. It all depends on the wind velocity.”

With the ferocity of a storm, some grass pollen grains can burst and release minute particles which are small enough for people to breathe deep into their lungs, triggering symptoms of asthma and a difficulty breathing.

This results in a large number of people developing sudden asthma symptoms and needing attention from emergency services.