Aerobiology: A multidisciplinary field in the
service of public health

 

Aerobiology is the study of the airborne particles of biological origin, and is focused on the sources, liberation, dispersal, deposition and impact of those particles on other living organisms and the environment. Aerobiology must therefore be considered as a multidisciplinary field which covers and serves surprisingly broad fields of sciences, such as allergology, plant pathology, bioclimatology, gene flow, biological invasions, climate change and even cultural heritage.

In Switzerland, MeteoSwiss is responsible for the National pollen monitoring network since 1993. As most of the aerobiology networks in Europe, it was developed by allergologists during the 1970s and the 1980s in relation with the rapid increase of the prevalence of respiratory allergies in the population. Close collaboration of specialists from different disciplines -botanists, meteorologists, climatologists, etc.- and the users of the information -in particular allergologists and patients’ organizations- was maintained over the years. It offers an optimal framework for developing innovative projects and useful tools for the information of concerned people. 

The analysis of data series allowed a better understanding of the processes influencing the airborne pollen concentrations. In a context of climate change, it was important to review the factors influencing the presence of pollen allergens in the air, and to estimate their possible impact on allergy. Observed changes affect in particular the timing of the pollen season. Earlier start and peak dates can be attributed to a large extent to the observed increase of spring temperatures. The duration of the overall pollen season was in many cases extended. The concentrations of airborne pollen also show varying patterns, increasing for a number of taxa, and decreasing for others. However, it was shown that the (long term) effects of the global climate warming are modulated by other factors at local and regional scales. Among those, human activities play an important role, e.g., by affecting the distribution of allergenic plants

It is important for allergy sufferers to be warned of possible exposure. Special effort was made in order to develop forecasts for the beginning of the season of the most important aeroallergens and pollen concentrations forecasts for the coming days. Several models were developed for this purpose. The most sophisticated integration of information is realised by the pollen module of the COSMO-ART numerical weather prediction model. It integrates information on vegetation distribution, phenological development of the plants, conditions for pollen release and transport in the atmosphere. Sedimentation and washout by the rain are also accounted for. Daily text forecasts are also provided by aerobiologists and meteorologists.

The main limitation of aerobiological information is the present state of monitoring technology. The widely used Hirst-trap and manual microscope counting system is very reliable, but the availability of data usually suffers from a delay of several days and the number of monitoring sites is limited by the number of specialists for pollen counting. In the last years, different technologies were tested for their capacity to measure airborne pollen concentrations and to differentiate, at least, the main allergenic taxa. The most promising system, that has the potential to bring aerobiology in a new era, is presently an air flow cytometer, offering the advantages of real-time measurement and high-resolution sampling. It will also be tested for its ability to identify and count other types of aerosols, such as spores, particulate pollutants and PM.

 

Some references:

Clot B. Trends in airborne pollen: an overview of 21 years of data in Neuchâtel (Switzerland). Aerobiologia 19: 227-234 (2003).

Taramarcaz P, et al. Progression and risk of ragweed allergy in Geneva: will Switzerland resist this invasion? Swiss Medical Weekly 135: 538-548 (2005).

Hilaire D, et al. Building models for daily pollen concentrations. Aerobiologia 28: 499-513 (2012).

Pauling A, et al. A method to derive vegetation distribution maps for pollen dispersion models using birch as an example. Int. J. Biometeorol. 56: 949-958 (2012).

Caillaud D, et al. Nonlinear short-term effects of airborne Poaceae levels on hay fever symptoms. Journal of Allergy and Clinical Immunology 130: 812-814 (2012).

Clot B, et al. The wind of change: effects of climate change on airborne pollen concentrations. Allergology and Immunology 9: 139-140 (2012).

Zink K, et al. EMPOL 1.0: A new parameterization of pollen emission in numerical weather prediction models. Geosci. Model. Dev. 6: 1961-1975 (2013).

Caillaud D, et al. Effects of airborne birch pollen levels on clinical symptoms of seasonal allergic rhinoconjunctivitis. Int. Arch. Allergy Immunol. 163:43-50 (2013).

Pauling A, et al. Towards optimized temperature sum parameterizations for forecasting the start of the pollen season. Aerobiologia 30: 45-57 (2014).

Galan C, et al. Pollen-monitoring: Minimum requirements and reproducibility of analysis. Aerobiologia 30: 385-395 (2014).

Gehrig R, et al. Alnus x spaethii pollen can cause allergies already at Christmas. Aerobiologia 31: 239-247 (2015).

Crouzy B, et al. All-optical automatic pollen identification: towards an operational system. Atmospheric Environment 140: 202-212 (2016).

 

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