A new study by KU Leuven and Sciensano, published in the scientific journal ‘Environment International’, reveals that pollen allergy and asthma should not be treated as a ‘pollen-only’ problem but as a climate-health issue.
It shows that the combination of higher temperatures, higher pollen concentrations, and air pollution leads to increased allergic symptoms and asthma in Belgium.
It had previously been shown that each factor individually negatively affects the respiratory and cardiovascular systems, but their interaction had not yet been investigated. This new study examined, for the first time, the combined effect of heat, pollen, and air pollution on pollen allergy and asthma.
Trigger for allergy and asthma
“Pollen remains the primary trigger for hay fever and asthma, but we see distinct peaks when high pollen concentrations coincide with extreme heat or elevated ozone levels,” says Professor Gijs Van Pottelbergh of KU Leuven, who led the study. Heat, pollen, and air pollution can reinforce each other.
High pollen levels combined with heat or ozone were associated with steeper increases in respiratory problems. Under these conditions, the risk of hay fever doubles, and asthma symptoms increase by approximately 24 percent.
Warning system
“It appears that air pollution and heat cause pollen to have a greater impact on our bodies. Often, just a few days are enough to trigger a strong effect,” adds Van Pottelbergh.
The researchers therefore advocate for better warning systems that monitor pollen, heat, and air pollution, so that at-risk groups can be warned in time to be extra vigilant.
The KULeuven-Sciensano study was based on 20 years of Flemish General Practitioners’ registration data with day-by-day measurements of temperature, pollen, fine particles, and ozone. It examined allergic rhinitis, hay fever, and asthma, not merely pollen concentrations.
Climate-change
A separate 2021 KU Leuven/Sciensano study examined 18 Brussels green spaces, mapping 5,940 trees and modeling how environmental changes could affect the risk of tree-pollen allergy.
This study indicated that more urban greenery remains beneficial overall, but cities should carefully select species and avoid concentrating highly allergenic trees.
Climate change is likely to make pollen-related illness harder to manage, not only by extending the pollen season, but by increasing the number of days when pollen, heat, and polluted air hit the respiratory system together.
