J. Sommer

The Long Range Transport of Birch (Betula) Pollen from Poland and Germany Causes Significant Pre-season Concentrations in Denmark

Background Birch pollen is highly allergic and has the potential for episodically long‐range transport. Such episodes will in general occur out of the main pollen season. During this time, allergy patients are unprotected and high pollen concentrations will therefore have a full allergenic impact.

Risk of exposure to airborne Ambrosia pollen from local and distant sources in Europe – an example from Denmark

BACKGROUND Ambrosia artemisiifolia L. is a noxious invasive alien species in Europe. It is an important aeroallergen and millions of people are exposed to its pollen. OBJECTIVE The main aim of this study is to show that atmospheric concentrations of Ambrosia pollen recorded in Denmark can be derived from local or more distant sources. METHODS This was achieved by using a combination of pollen measurements, air mass trajectory calculations using the HYPLIT model and mapping all known Ambrosia locations in Denmark and relating them to land cover types. RESULTS The annual pollen index recorded in Copenhagen during a 15-year period varied from a few pollen grains to more than 100. Since 2005, small quantities of Ambrosia pollen has been observed in the air every year. We have demonstrated, through a combination of Lagrangian back-trajectory calculations and atmospheric pollen measurements, that pollen arrived in Denmark via long-distance transport from centres of Ambrosia infection, such as the Pannonian Plain and Ukraine. Combining observations with results from a local scale dispersion model show that it is possible that Ambrosia pollen could be derived from local sources identified within Denmark. CONCLUSIONS The high allergenic capacity of Ambrosia pollen means that only small amounts of pollen are relevant for allergy sufferers, and just a few plants will be sufficient to produce enough pollen to affect pollen allergy sufferers within a short distance from the source. It is necessary to adopt control measures to restrict Ambrosia numbers. Recommendations for the removal of all Ambrosia plants can effectively reduce the amount of local pollen, as long as the population of Ambrosia plants is small.

Copenhagen: A harbinger for ragweed (Ambrosia) in Northern Europe under climate change?

Pollen grains from the genus Ambrosia spp. (ragweed) are considered to be very potent aeroallergens. The threshold value for clinical symptoms for ragweed pollen grains for the majority of sensitised patients is below 20 grains/m 3 (Jäger, 2000; Taramaracaz et al., 2005). Ambrosia pollen appears to induce asthma about twice as often as other pollen (Jäger, 2000; White and Bernstein, 2003). Ambrosia is present in the Czech Republic, Slovakia and Hungary, which may serve as source areas for long range transport to Poland and maybe also Denmark (Smith et al., 2008). As such mbrosia pollen grains reported in the Danish pollen and spore traps have mainly been ascribed to long distance transport. The growth season in Denmark has until now been considered to short for Ambrosia to flower and produce seeds. Ambrosia seeds have been found in significant quantities in imported bird seed in Denmark. Despite the limited growth season, Ambrosia is therefore found every year in urban areas such as gardens. However, with the climate changes observed over the last 20 years growth season for Ambrosia has most likely been extended. Furthermore, due to the urban heat island effect, the growth season in Copenhagen is likely to be extended compared to rural areas. It is therefore likely that Ambrosia has the potential to flower in Denmark, especially Copenhagen. This paper examines the hypothesis that Ambrosia artemisiifolia has established itself as a flowering species in Copenhagen. Ambrosia pollen data were collected by volumetric spore trap at Copenhagen (1979-2007) following the standard method of the Danish Asthma-Allergy Association. All available bihourly Ambrosia pollen counts where combined with results from a flexible trajectory model (e.g. Skjøth et al., 2008). A phenological model for Ambrosia was applied to study the potential pollen release within Copenhagen and supplemented with phenological field studies for the year 2008. Ambrosia was counted with certainty since 1997. The annual count varied from 8 to 120 in 1998 and 2002. Two years with high counts seems to be related to long distance transport and the years with the low counts show an increasing tendency. Bihourly pollen records were examined and each bihourly record of Ambrosia is analysed with respect to arrival times and correlated with a back trajectory analysis. The majority of single pollen grains are found in the afternoon records, suggesting a possible local population, as Ambrosia pollen are released during daytime (Ogden et al., 1969). The majority of back-trajectories for the bihourly records of Ambrosia show a westerly wind approach passing the Copenhagen area. For bihourly records above 1 grain this tendency is less pronounced. On the other hand, the two possible long distance transport episodes have a more southerly direction suggesting Ukraine, Poland and the Pannonian plain as possible source areas. Pollen grains arriving in the morning mainly approached from the south east, where as those arriving at night time have no predominating source areas. The results from the phenological model suggest an increased growth season for Ambrosia during the 30 year period within the Copenhagen area, thus increasing the possibility for Ambrosia to flower. This was verified with the field study, which showed a population of flowering Ambrosia plants in Copenhagen in 2008. The hypothesis that Ambrosia artemisiifolia has established it self as a flowering species in Copenhagen is therefore supported. The annual pollen counts show an increasing tendency, indicating an increased local population. The bihourly counts show a larger number of observations during the daytime compared to night time. This also indicates a local population. The back trajectories indicate long distance transport from the South and such episodes are found in 1999 and 2002. Back trajectories correlated with low daytime pollen counts show that air masses have passed the Copenhagen area, again supporting the hypothesis. The phenological flowering model indicates increased length of growth season for Ambrosia during the 30 year period. This increases the possibility of Ambrosia flowering in Copenhagen. The result from the phenological model is further supported by the observations of a flowering Ambrosia population in Copenhagen in 2008. The combination of observations and model calculations support the hypothesis that Ambrosia is a systematically flowering species in Copenhagen. The main source to Ambrosia seeds is likely to be birdseed imported from countries such as Hungary. Whether Ambrosia has the potential to reproduce by seed in Denmark is not known. However, future climate projections for Denmark are similar to the current climate found in areas such as France and the Pannonian Plain. These areas are the most severe Ambrosia polluted Climate Change: Global Risks, Challenges and Decisions IOP Publishing IOP Conf. Series: Earth and Environmental Science 6 (2009) 142031 doi:10.1088/1755-1307/6/4/142031