Allergy sufferers from Tokyo to London are struggling as pollen levels surge in cities, possibly due to a preference for male trees
In 2016, Melbourne experienced a rare and extreme case of thunderstorm asthma that led to ten deaths and 8,500 people being admitted to hospital in one day. Ambulance dispatchers struggled to cope with 1,900 calls in the space of five hours, and one hospital ran out of Ventolin asthma inhalers. The storm had caused grass pollen to burst in the air, creating tiny particles that caused serious breathing problems when inhaled.
Meanwhile, in London, landscaping practices have led to an abundance of tree pollen, aggravating hay fever, according to a horticultural expert. Landscapers in the UK capital and around the world plant predominantly male trees because they are less messy than female trees, which shed seeds, fruits or pods, says Thomas Leo Ogren, creator of the Ogren Plant Allergy Scale. The problem is that while these [male] trees and plants are litter-free, they all produce abundant allergenic pollen.
Some are dioecious plants, which have their own distinct sex, and some are monoecious plants (those with male and female flowers on the same plant) that have been cloned to be male. The last few times I was in London, for example, almost every single willow tree I saw was now a male clone; almost all of the bay trees being sold and planted were males; virtually all of the many species of poplar trees sold and planted are now male, says Ogren.
So is one of these the worst city in the world for pollen allergies?
The incident in Melbourne certainly caused some academics to ponder whether the city is the allergy capital of the world, especially because Melbourne has had three other recorded epidemics of thunderstorm asthma since the late 1980s.