Abstract
Airborne pollen is a major cause of allergic rhinitis, affecting between 10 and 30% of the population in Belgium, the Netherlands, and Luxembourg (Benelux). Allergenic pollen is produced by wind pollinating plants and released in relatively low to massive amounts. Current climate changes, in combination with increasing urbanization, are likely to affect the presence of airborne allergenic pollen with respect to exposure intensity, timing as well as duration. Detailed analysis of long-term temporal trends at supranational scale may provide more comprehensive insight into these phenomena. To this end, the Spearman correlation was used to statistically compare the temporal trends in airborne pollen concentration monitored at the aerobiological stations which gathered the longest time-series (30–44 years) in the Benelux with a focus on the allergenic pollen taxa: Alnus, Corylus, Betula, Fraxinus, Quercus, Platanus, Poaceae, and Artemisia. Most arboreal species showed an overall trend toward an increase in the annual pollen integral and peak values and an overall trend toward an earlier start and end of the pollen season, which for Betula resulted in a significant decrease in season length. For the herbaceous species (Poaceae and Artemisia), the annual pollen integral and peak values showed a decreasing trend. The season timing of Poaceae showed a trend toward earlier starts and longer seasons in all locations. In all, these results show that temporal variations in pollen levels almost always follow a common trend in the Benelux, suggesting a similar force of climate change-driven factors, especially for Betula where a clear positive correlation was found between changes in temperature and pollen release over time. However, some trends were more local-specific indicating the influence of other environmental factors, e.g., the increasing urbanization in the surroundings of these monitoring locations. The dynamics in the observed trends can impact allergic patients by increasing the severity of symptoms, upsetting the habit of timing of the season, complicating diagnosis due to overlapping pollen seasons and the emergence of new symptoms due allergens that were weak at first.
Highlights
It is widely recognized that the prevalence of respiratory allergies such as asthma and allergic rhinitis is globally increasing, especially in the industrialized world [1, 2]
The season timing of Poaceae showed a trend toward earlier starts and longer seasons in all locations. These results show that temporal variations in pollen levels almost always follow a common trend in the Benelux, suggesting a similar force of climate change-driven factors, especially for Betula where a clear positive correlation was found between changes in temperature and pollen release over time
The decadal increasing trends appear to be clear when the Alnus Annual Pollen Integral (API) started from low values in the first decades to higher values in the last decade (Brussels, De Haan, and Luxembourg); this decadal increase from the first to the last decade was significant for Brussels and De Haan
Summary
It is widely recognized that the prevalence of respiratory allergies such as asthma and allergic rhinitis is globally increasing, especially in the industrialized world [1, 2]. For Belgium, the Netherlands and Luxembourg (whose usual acronym is Benelux) the prevalence of asthma varies between 10 and 15% of the population [3] and for allergic rhinitis it is estimated to be 10–30% [4,5,6]. The World Meteorological Organization (WMO) reported that 2020 was 1.2 ± 0.1◦C warmer than the pre-industrial baseline (1850– 1900) [12]. These long-term changes in the climate have multiple impacts on the environment and on health
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