Predicting the onset of Betula pendula flowering in Poznan (Poland) using remote sensing thermal data.

Due to the urban heat island effect, the time of plant pollination might markedly vary within the area of a city. However, existing pollen forecasts do not reflect the spatial variations in the pollen release time within a heterogeneous urban environment. The main objective of this study was to model the spatial pattern of flowering onset (and thus the moment of pollen release) in silver birch (Betula pendula Roth.) in Poznan (Western Poland) using land surface temperature (LST) data and in situ phenological observations. The onset of silver birch flowering was observed at 34 urban and rural sites (973 trees) in Poznan from 2012 to 2014. Forty-four thermal variables were retrieved from MODerate Resolution Imaging Spectroradiometer (MODIS) data. To predict the spatio-temporal distribution of B. pendula flowering onset dates in a city, the ordinary and partial least squares, support vector machine and random forest regression models were applied. The models' performance was examined by an internal repeated k-fold cross-validation and external validation with archival phenological data (2010). Birch flowering began significantly earlier in the urban sites compared to the rural sites (from -1.4 days in 2013, to -4.1 days in 2012). The maximum March LST difference between the urban and rural sites reached 2.4 °C in 2013 and 4.5 °C in 2012. The random forest model performed best at validation stage, i.e. the root mean square error between the predicted and observed onset dates was 1.461 days, and the determination coefficient was 0.829. A calibrated model for predicting the timing of flowering in a heterogeneous city area is an important step in developing a fine-scale forecasting system that can directly estimate pollen exposure in places where allergy sufferers live. Importantly, by incorporating only pre-flowering thermal data into the model, location-specific allergy forecasts can be delivered to the public before the actual flowering time.

Variation of the group 5 grass pollen allergen content of airborne pollen in relation to geographic location and time in season.

BACKGROUND: Allergies to grass pollen are the number one cause of outdoor hay fever. The human immune system reacts with symptoms to allergen from pollen. OBJECTIVE: We investigated the natural variability in release of the major group 5 allergen from grass pollen across Europe. METHODS: Airborne pollen and allergens were simultaneously collected daily with a volumetric spore trap and a high-volume cascade impactor at 10 sites across Europe for 3 consecutive years. Group 5 allergen levels were determined with a Phl p 5-specific ELISA in 2 fractions of ambient air: particulate matter of greater than 10 µm in diameter and particulate matter greater than 2.5 µm and less than 10 µm in diameter. Mediator release by ambient air was determined in FcεRI-humanized basophils. The origin of pollen was modeled and condensed to pollen potency maps. RESULTS: On average, grass pollen released 2.3 pg of Phl p 5 per pollen. Allergen release per pollen (potency) varied substantially, ranging from less than 1 to 9 pg of Phl p 5 per pollen (5% to 95% percentile). The main variation was locally day to day. Average potency maps across Europe varied between years. Mediator release from basophilic granulocytes correlated better with allergen levels per cubic meter (r(2) = 0.80, P < .001) than with pollen grains per cubic meter (r(2) = 0.61, P < .001). In addition, pollen released different amounts of allergen in the non-pollen-bearing fraction of ambient air, depending on humidity. CONCLUSION: Across Europe, the same amount of pollen released substantially different amounts of group 5 grass pollen allergen. This variation in allergen release is in addition to variations in pollen counts. Molecular aerobiology (ie, determining allergen in ambient air) might be a valuable addition to pollen counting.

Clinical relevance of Corylus pollen in Poznan, western Poland.

BACKGROUND: In Central Europe, hazel (Corylus sp.) pollen is considered to be an important aeroallergen in early spring. OBJECTIVE: This study examines hazel pollen levels in Poznan, western Poland, and the clinical relevance of this aeroallergen in the city. METHODS: Corylus pollen data (1996-2010) were obtained by volumetric spore trap located near the centre of Poznan. Clinical data (2006-2010), i.e. skin prick test (SPT) and allergen-specific IgE measurements (asIgE), were supplied by the Allergy Diseases Diagnostic Centre in Poznan. RESULTS: Mean diurnal hazel pollen concentrations peaked around 14:00-16:00 when mean bi-hourly pollen concentrations were ~60 P m(-3). Onset of the hazel pollen season varied up to 87 days annually, and was significantly (r=-0.647; p<0.01) related to mean maximum temperature during late December. SPT data revealed that ~11% of allergy patients had positive skin reactions to Corylus pollen allergens, and most of these (94.4%) reacted to pollen allergens from other members of the Betulaceae family - alder or birch. Of those sensitized, 53% suffered from atopic dermatitis. Of patients examined for serum asIgE, 26.0% had asIgE measurements in classes 5 and 6. CONCLUSIONS: Hazel pollen has a detrimental effect on the allergic population of Poznan, with more than half of those sensitised to hazel pollen allergens showing symptoms of atopic dermatitis. Hazel pollen concentrations reach levels recognized as being able to induce allergy symptoms, especially in the afternoon and early evening when many people are returning home from work. The cross-reactivity with other members of the Fagales order also increases the allergenic potential of hazel pollen.

Trends in atmospheric concentrations of weed pollen in the context of recent climate warming in Poznan (Western Poland).

A significant increase in summer temperatures has been observed for the period 1996-2011 in Poznan, Poland. The phenological response of four weed taxa, widely represented by anemophilous species (Artemisia spp., Rumex spp. and Poaceae and Urticaceae species) to this recent climate warming has been analysed in Poznan by examining the variations in the course of airborne pollen seasons. Pollen data were collected by 7-day Hirst-type volumetric trap. Trends in pollen seasons were determined using Mann-Kendall test and Sen's slope estimator, whereas the relationships between meteorological and aerobiological data were established by Spearman's rank correlation coefficient. Significant trends in pollen data were detected. The duration of pollen seasons of all analysed taxa increased (from +2.0 days/year for Urticaceae to +3.8 days/year for Rumex), which can be attributed to a delay in pollen season end dates rather than earlier start dates. In addition, the intensity of Artemisia pollen seasons significantly decreased and correlates with mean July-September daily minimum temperatures (r = -0.644, p < 0.01). In contrast, no significant correlations were found between temperature and characteristics of Rumex pollen seasons. The results of this study show that observed shifts in weed pollen seasons in Poznan, i.e. longer duration and later end dates, might be caused by the recorded increase in summer temperature. This influence was the strongest in relation to Artemisia, which is the taxon that flowers latest in the year. The general lack of significant correlations between Rumex and Urticaceae pollen seasons and spring and/or summer temperature suggests that other factors, e.g. land use practices, could also be partially responsible for the observed shifts in pollen seasons.