Uneasy atmosphere

Rethinking urban planting and better air monitoring for pollen and spores could help reduce symptoms for seasonal hay fever sufferers.

- Nicky Pellegrino

The warm, wet winter has meant hay fever season arrived early this year and pollen counts are forecast to be high. For about 20% of New Zealanders that means dealing with unpleasant symptoms, such as itchy and watery eyes, frequent sneezing, headaches and dizziness, sore throats and blocked noses.

Urban hay fever sufferers often blame the surrounding countryside for their symptoms, but the latest research suggests that may not be the case.

Philip Taylor, of La Trobe University in Melbourne, was part of a team of international scientists who have studied how far hay fever causing particles such as pollen and fungi can travel in the atmosphere.

They took air samples at the Amazon Tall Tower Observatory, a base in the middle of the rainforest of northern Brazil which has two research masts, the taller of which is 325m.

"It's the last pristine air on the planet," Taylor says. 

Clouds of Saharan dust have been detected there, having blown thousands of kilometres across the Atlantic Ocean.

However, pollen particles are bigger, and the team's sampling showed that rather than rising into the air and scattering over long distances, pollen tends to travel low to the ground.

These giant aerosols generally don't achieve the height required for long-range transport, explains Taylor. "You need a lot of atmospheric force, a convective storm [strong thunderstorm] to make that happen." 

Biophysics is telling us that the causes of urban hay fever are most likely to be closer to home, and Taylor points to ryegrass as a particular problem. We use it in our city gardens, parks and sports grounds, as well as in rural areas for animals to graze on.