This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: When most Australians say 'spring is in the air,' they're speaking metaphorically, as the days become longer and warmer. But in Melbourne, the meaning is a touch more literal.
Spring is the time of year when Melbourne's air becomes laden with pollen from plants beginning to flower. And while those budding blooms bring joy to many people, for about one in five Melburnians, springtime means an uptick in respiratory conditions like hay fever and seasonal asthma. The main culprits are allergens in grass pollen.
Every day from October to December, Melbourne's pollen count is measured and published, so hay fever sufferers know exactly what they're breathing. While current air monitoring can distinguish grass pollen from other types, it can't identify which grass is producing it. This is because all grass pollen can look fairly similar under the microscope.
So in Melbourne, we don't know whether grass pollen comes from a single type of grass or many. We also don't know how that mix changes across the season, or from one year to the next. But why does it matter so much to know exactly which grass is producing which pollen?
Because some grasses are far more allergenic than others, and knowing someone's pollen exposure can help allergists choose the best treatment. On top of this, severe spring storms can trigger thunderstorm asthma events, which hit Melbourne on average once every seven years. Because these events are linked to ryegrass pollen, tracking when ryegrass is in the air helps flag periods of highest risk.
In 2016, Melbourne experienced the world's largest epidemic thunderstorm asthma event, resulting in more than 3,500 emergency department presentations, a 672% increase in respiratory hospital admissions and 10 deaths. To get a clearer picture of the pollen in Melbourne's air, our team used DNA metabarcoding to identify what was in weekly air samples collected over two consecutive years. DNA metabarcoding is a method for identifying all the species that have left traces of genetic material, known as environmental DNA, in a sample, whether that's seawater, soil or, in our case, air.
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