Start Of Pollen Season Research Articles

Forecast models for start and peak dates of Poaceae pollen season in Tétouan (NW Morocco) using multiple regression analysis.

Poaceae pollen is one of the most widespread sources of aeroallergens in the world. The aim of this study is to build predictive models for the pollen season start day (PSsd) and peak dates of the Poaceae pollen season and thus give an overview of the climatic parameters that have the greatest influence. In Tétouan, sampling was carried out using a volumetric spore trap of the Burkard Hirst type. The relationships between the PSsd, peak dates and meteorological parameters were determined using correlation analysis. The models were constructed using multiple regression analysis with data from 2008 to 2019 and tested on data from 2022. The PSsd was especially significantly influenced by minimum temperature during winter and precipitation in the autumn of the previous year. The peak dates were significantly correlated with precipitation in January, March and April, but not with temperature. Three models were obtained for each of the season's parameters; the most accurate model for the PSsd explained a variability of 61% and includes as main predictors rainfall from the autumn of the previous year and the mean daily average temperature from 23 February to 8 March. The two most efficient peak dates models included precipitation in January and April as the main predictor variables, and explained greater variability (87 and 88%). Precipitation in autumn and the mean daily and the sum of minimum temperature in winter, showed significant decreasing tendencies. However, the PSsd trend delay was not statistically significant. This study draws the importance of the weather during preseason for grass pollen production and emphasises the usefulness of the models for allergic patients to take preventive measures and for healthcare professionals in allergy therapy.

The South African Pollen Monitoring Network: Insights from 2years of national aerospora sampling (2019-2021).

Pollen monitoring has been discontinuously undertaken in South Africa, a country with high biodiversity, a seasonal rainfall gradient, and nine biomes from arid to subtropical. The South African Pollen Monitoring Network was set up in 2019 to conduct the first long-term national aerospora monitoring across multiple biomes, providing weekly reports to allergy sufferers and healthcare providers. Daily airborne pollen concentrations were measured from August 2019 to August 2021 in seven cities across South Africa. Updated pollen calendars were created for the major pollen types (>3%), the average Annual Pollen Index over 12 months was calculated, and the results were compared to available historical data. The main pollen types were from exotic vegetation. The most abundant taxa were Poaceae, Cupressaceae, Moraceae and Buddleja. The pollen season start, peak and end varied widely according to the biome and suite of pollen taxa. The main tree season started in the last week of August, peaked in September and ended in early December. Grass seasons followed rainfall patterns: September-January and January-April for summer and winter rainfall areas, respectively. Major urban centres, for example, Johannesburg and Pretoria in the same biome with similar rainfall, showed substantive differences in pollen taxa and abundance. Some major differences in pollen spectra were detected compared with historical data. However, we are cognisant that we are describing only 2years of data that may be skewed by short-term weather patterns. Differences in pollen spectra and concentrations were noted across biomes and between geographically close urban centres. Comparison with historical data suggests pollen spectra and seasons may be changing due to anthropogenic climate change and landscaping. These data stress the importance of regional and continuous pollen monitoring for informed care of pollinosis.

Trends and future projections of Olea flowering in the western Mediterranean: The example of the Alentejo region (Portugal)

Olives are one of the most economically relevant crops in the Mediterranean area but this region is experiencing a strong warming due to climate change. Therefore, it would be of great interest to estimate the possible implications of climate change on olive flowering timing by modelling its thermal requirements, and aerobiological records have proved to be a useful tool for monitoring regional olive phenology. Recently, a new phenological modelling framework has been developed called PhenoFlex. It has shown excellent results in estimating the thermal requirements of fruit trees. However, this framework has not previously been applied to olive trees or tested using aerobiological data, which could present greater spatial distribution than in situ phenological observations. This study has a threefold aim: i) to detect the trends in the main pollen season start date of Olea during the past 25 years in a western Mediterranean region (Alentejo, Portugal); ii) to evaluate the applicability of the PhenoFlex modelling framework to olive aerobiological data, and iii) to use the modelled parameter estimates to evaluate the influence of projected future climate change scenarios on Olea flowering regional onset dates. Our results showed that global warming had not produced any significant trend in the olive flowering onset dates until the present time, and they are not expected to do so in the near future, either. A temperature increase during winter was observed that is delaying the fulfilment of the Olea chilling requirements, but this is compensated for by a reduction in the forcing period due to higher temperatures observed during spring. However, our study points out a significant increase in the interannual variability of flowering onset dates, which could compromise fruit development and adversely affect the yield, raising uncertainty in olive fruit production in the near future.

Determination of ragweed allergen Amb a 1 distribution in aerosols using ELISA and immunogold scanning electron microscopy.

Ragweed as an invasive species in Europe has become more important for allergy sufferers in the last decade. Because pollen fractions can be found in the respirable fraction of aerosols, they can generate severe disease progressions. To obtain information about the concentration and distribution of 1 of the main ragweed allergens Ambrosia artemisiifolia 1 in the air of Vienna, PM10 and PM2.5 fine dust filters were analyzed. Standard fine dust filters used for air quality monitoring were analyzed via ELISA and immunogold scanning electron microscopy. Via ELISA it was possible to show that already at pollen season start in August a recognizably high A artemisiifolia 1 concentration can be found. In addition, the allergen concentration in the air stays comparatively high after the peak season has ended even when the pollen concentration drops to a moderate level. The immunogold electron microscopy investigation directly applied on filters shows that the allergen can be found on organic as well as on mixtures of organic and inorganic particles. Afirst semistatistical analysis of the labeled particle sizes indicates that a large number of the allergen carriers can be found within the smallest particle size range. Nevertheless, further investigations are needed to obtain enough particle counts for a significant statistical analysis. It was possible to show that reliable results can be obtained from ELISA and immunogold scanning electron microscopy directly applied on filters that are used in air qualitymonitoring sites. By adaptation of the used protocols, itshould be possible to obtain respective information aboutfurther allergens.

Response to high-altitude triggers in seasonal asthmatics on and off inhaled corticosteroid treatment

BackgroundDue to the effects of climate change, winter sport enthusiasts will be increasingly forced to stay at higher altitudes. High altitude (HA) environmental factors such as cold temperature, physical exertion, and hypoxia with subsequent hypocapnia due to hyperventilation have been shown to induce bronchoconstriction. With bronchial asthma being highly prevalent, asthmatics also will be increasingly exposed to HA environment and might experience increasing symptoms. MethodsWe analysed the effects of HA factors at around 2600 m a.s.l. (metres above sea level) on lung function in mild seasonal asthmatics while they were routinely off (January) and on (March, after start of lowland pollen season) low-dose inhaled corticosteroid (ICS) treatment (n = 10), and matched healthy controls (n = 11). ResultsWithout inhaled corticosteroid (ICS) treatment mean FEV1 in asthmatics was 230 ml lower after exercise at HA compared to low altitude (LA, p < 0.05), while in healthy controls there was no significant difference. This decrease was mainly induced by cold and exercise at HA. During ICS treatment, this decrease was prevented. Methacholine response was reduced at HA compared to LA. ConclusionsThe decrease of FEV1 in response to a combination of hypoxia, cold, and exercise is prevented by ICS treatment in mild, seasonal asthmatics. However, the FEV1 response to high altitude factors was overall small.

Aeroallergens and Climate Change in Tulsa, Oklahoma: Long-Term Trends in the South Central United States.

Climate change is having a significant effect on many allergenic plants resulting in increased pollen production and shifts in plant phenology. Although these effects have been well-studied in some areas of the world, few studies have focused on long-term changes in allergenic pollen in the South Central United States. This study examined airborne pollen, temperature, and precipitation in Tulsa, Oklahoma over 25 to 34 years. Pollen was monitored with a Hirst-type spore trap on the roof of a building at the University of Tulsa and meteorology data were obtained from the National Weather Service. Changes in total pollen intensity were examined along with detailed analyses of the eight most abundant pollen types in the Tulsa atmosphere. In addition to pollen intensity, changes in pollen season start date, end date, peak date and season duration were also analyzed. Results show a trend to increasing temperatures with a significant increase in annual maximum temperature. There was a non-significant trend toward increasing total pollen and a significant increase in tree pollen over time. Several individual taxa showed significant increases in pollen intensity over the study period including spring Cupressaceae and Quercus pollen, while Ambrosia pollen showed a significant decrease. Data from the current study also indicated that the pollen season started earlier for spring pollinating trees and Poaceae. Significant correlations with preseason temperature may explain the earlier pollen season start dates along with a trend toward increasing March temperatures. More research is needed to understand the global impact of climate change on allergenic species, especially from other regions that have not been studied.

Satellite-based phenology products and in-situ pollen dynamics: A comparative assessment

Ongoing climate variability and change is impacting pollen exposure dynamics among sensitive populations. However, pollen data that can provide beneficial information to allergy experts and patients alike remains elusive. The lack of high spatial resolution pollen data has resulted in a growing interest in using phenology information that is derived using satellite observations to infer key pollen events including start of pollen season (SPS), timing of peak pollen season (PPS), and length of pollen season (LPS). However, it remains unclear if the agreement between satellite-based phenology information (e.g. start of season: SOS) and the in-situ pollen dynamics vary based on the type of satellite product itself or the processing methods used. To address this, we investigated the relationship between vegetation phenology indicator (SOS) derived from two separate sensor/satellite observations (MODIS, Landsat), and two different processing methods (double logistic regression (DLM) vs hybrid piecewise logistic regression (HPLM)) with in-situ pollen season dynamics (SPS, PPS, LPS) for three dominant allergenic tree pollen species (birch, oak, and poplar) that dominate the springtime allergy season in North America. Our results showed that irrespective of the data processing method (i.e. DLM vs HPLM), the MODIS-based SOS to be more closely aligned with the in-situ SPS, and PPS while upscaled Landsat based SOS had a better precision. The data products obtained using DLM processing methods tended to perform better than the HPLM based methods. We further showed that MODIS based phenology information along with temperature and latitude can be used to infer in-situ pollen dynamic for tree pollen during spring time. Our findings suggest that satellite-based phenology information may be useful in the development of early warning systems for allergic diseases.

Recent advancements in the use of remote sensing observations to inform ground level pollen dynamics

BACKGROUND AND AIM: Pollen information (e.g., pollen seasons and concentrations) is highly needed for allergy disease studies. However, in-situ pollen data from stations are still limited. Satellite data with repeated observations and global coverage provide the possibility to inform ground pollen dynamics over large areas. This study aims to improve the understanding of the relationship between vegetation phenology and pollen season, for its potential in developing fine spatiotemporal pollen maps over large areas. METHODS: We developed a framework to explore the relationship between the onset of vegetation phenology and pollen season. First, we derived pollen indicators using a double-Gaussian function and the collected pollen concentration data at five in-situ pollen stations. Next, we estimated vegetation phenology indicators and their interannual variability using satellite derived vegetation index. Finally, we explored the relationship between the indicators of pollen and phenology, and evaluated the scale effect of the relationship at the five stations during 2001–2015. RESULTS:Although indicators of pollen season (i.e., start of pollen season, SPS) and the vegetation phenology (i.e., start of season, SOS) vary spatially and temporally over stations, they exhibit consistent temporal trends during 2001-2015. SOS derived from finer Landsat satellite observations outperforms that from MODIS observations with a coarse spatial resolution. Our results indicate that satellite-derived SOS can serve as a proxy for pollen seasons in birch dominated areas. CONCLUSIONS:In this study, we explored the relationship between satellite-derived vegetation phenology and station-based pollen season at stations. Our results indicate that satellite-derived phenology can be used as an indicator for pollen dynamics over large areas, and therefore provides the possibility to assess the risk of respiratory allergies, especially in highly heterogeneous urban areas with high spatiotemporal satellite observations. KEYWORDS: Satellite remote sensing, Phenology, Start of Season, Pollen

Analysis of changes in Betula pollen season start including the cycle of pollen concentration in atmospheric air.

Birch belongs to the most important allergenic taxa in Europe, therefore information on the start dates of the pollen season is very important for allergists and their patients as well as for climatologists. The study examined changes in the start of the birch pollen season as well as determined the trend of these changes. Pollen monitoring was performed in Lublin (eastern Poland) in the period 2001–2019 using the volumetric method. The Makra-test was used to detect periods with significantly higher or lower average of the onset than the average for the whole dataset. Two significant falls in the average of the pollen season start were found in 2007 and 2014. Besides, taking into account the 2-3-year rhythm of high and low concentrations of birch pollen in the atmospheric air, linear trends were fitted for the subsets of high and low abundance seasons. Significant changes in Betula pollen season start dates were only determined for the highly abundance seasons, while the results for seasons with a low concentration did not allow rejecting the hypothesis about the lack of a linear trend in the changes in the studied parameter. Moreover, a significant polynomial relationship was found between the beginning of a pollen season and the average values of monthly temperatures preceded a season. These analyses show that the start dates of the Betula pollen season are getting significantly earlier. The dynamics of changes differ between seasons with high and low concentrations of pollen.

Changes in Timing of Spring Onset, Pollen Exposure, and Burden of Allergic Disease in the Northeastern United States

BACKGROUND AND AIM: Ongoing climate variability and change is altering the timing of spring onset, a critical event that signifies the start of tree pollen season in North America. There is a paucity of data regarding how such changes in the timing of spring onset impact burden of allergic disease in the Northeast United States. METHODS: We processed Landsat and MODIS observations for New York and Maryland during 2001-2015 to derive the start of spring (SOS) using double logistic model and aggregated them to county level. We then calculated yearly deviations in SOS for each county for MD and NY from their respective long term median values (2001-2015). These deviations were categorized as very early, early, normal, late and very late. We linked these yearly deviations in SOS with asthma hospitalization for MD and NY during 2001-2015, based on the county of residence. We used general additive (quasi Poisson) and mixed-effect (negative binomial) models to investigate the association between changes in the timing of spring onset and asthma hospitalization. RESULTS:Very early onset of spring was associated with a 17% increase in asthma hospitalization in Maryland during spring season (incident rate ratio [IRR], 1.17; 95% CI, 1.07-1.28). Likewise late onset of spring was associated with a 7% increase in asthma hospitalization (IRR, 1.07; 95% CI, 1.00-1.15). Adjustments for extreme heat event and particulate matter with aerodynamic diameter less than 2.5 microns (PM2.5) did not change result for very early onset of spring, but late onset was no longer statistically significant. Similar analysis for NY is ongoing and will be covered in the presentation. CONCLUSIONS:Our findings suggest that early onset of spring that are tied to warming climate may increase burden of allergic disease such as asthma. KEYWORDS: Climate Change, phenology, asthma, pollen, allergy

A systematic review of the effects of temperature and precipitation on pollen concentrations and season timing, and implications for human health.

Climate and weather directly impact plant phenology, affecting airborne pollen. The objective of this systematic review is to examine the impacts of meteorological variables on airborne pollen concentrations and pollen season timing. Using PRISMA methodology, we reviewed literature that assessed whether there was a relationship between local temperature and precipitation and measured airborne pollen. The search strategy included terms related to pollen, trends or measurements, and season timing. For inclusion, studies must have conducted a correlation analysis of at least 5 years of airborne pollen data to local meteorological data and report quantitative results. Data from peer-reviewed articles were extracted on the correlations between seven pollen indicators (main pollen season start date, end date, peak date, and length, annual pollen integral, average daily pollen concentration, and peak pollen concentration), and two meteorological variables (temperature and precipitation). Ninety-three articles were included in the analysis out of 9,679 articles screened. Overall, warmer temperatures correlated with earlier and longer pollen seasons and higher pollen concentrations. Precipitation had varying effects on pollen concentration and pollen season timing indicators. Increased precipitation may have a short-term effect causing low pollen concentrations potentially due to "wash out" effect. Long-term effects of precipitation varied for trees and weeds and had a positive correlation with grass pollen levels. With increases in temperature due to climate change, pollen seasons for some taxa in some regions may start earlier, last longer, and be more intense, which may be associated with adverse health impacts, as pollen exposure has well-known health effects in sensitized individuals.

A First Pre-season Pollen Transport Climatology to Bavaria, Germany.

Climate impacts on the pollen season are well-described however less is known on how frequently atmospheric transport influences the start of the pollen season. Based on long-term phenological flowering and airborne pollen data (1987–2017) for six stations and seven taxa across Bavaria, Germany, we studied changes in the pollen season, compared pollen and flowering season start dates to determine pollen sources, and analyzed the likelihood of pollen transport by HYSPLIT back trajectories. Species advanced their pollen season more in early spring (e.g., Corylus and Alnus by up to 2 days yr−1) than in mid spring (Betula, Fraxinus, Pinus); Poaceae and Artemisia exhibited mixed trends in summer. Annual pollen sums mainly increased for Corylus and decreased for Poaceae and Artemisia. Start of pollen season trends largely deviated from flowering trends, especially for Corylus and Alnus. Transport phenomena, which rely on comparisons between flowering and pollen dates, were determined for 2005–2015 at three stations. Pre-season pollen was a common phenomenon: airborne pollen was predominantly observed earlier than flowering (median 17 days) and in general, in 63% of the cases (except for Artemisia and Poaceae, and the alpine location) the pollen sources were non-local (transported). In 54% (35%) of these cases, back trajectories confirmed (partly confirmed) the pre-season transport, only in 11% of the cases transport modeling failed to explain the records. Even within the main pollen season, 70% of pollen season start dates were linked to transport. At the alpine station, non-local pollen sources (both from outside Bavaria as well as Bavarian lowlands) predominated, in only 13% of these cases transport could not be confirmed by back trajectories. This prominent role of pollen transport has important implications for the length, the timing, and the severity of the allergenic pollen season, indicating only a weak dependency on flowering of local pollen sources.

Consequences of climate change on airborne pollen in Bavaria, Central Europe

Climate change affects the reproductive life cycles of plants, including pollen production, which has consequences for allergic respiratory diseases. We examined climatic trends at eight locations in Bavaria, Southern Germany, with pollen time series of at least 10 years (up to 30 years in Munich). Climate change in Bavaria was characterized by a rise in temperature, but not during the winter. There is also a trend towards a more continental climate in Bavaria, which is significant in the Alps in the south of the territory. The influence of climate change depended on pollen type. Wind-pollinated arboreal species (e.g. Alnus, Betula and Cupressaceae/Taxaceae) showed advances in the start and end dates of pollen seasons and an increase in pollen load. These changes correlated negatively with late-winter (February) and spring temperatures (April). For herbaceous species, like Poaceae and Urticaceae, an earlier season was observed. Although precipitation is not a limiting factor in Southern Germany, water availability in the spring did influence the magnitude of grass pollen seasons. The effect of climatic change on the characteristics of pollen seasons was also more pronounced at higher altitudes, significant at > 800 m above sea level. Our results show that trends for start, end dates and intensity were similar at all locations, but only statistically significant at some. If we assume that earlier and more intense pollen seasons result in increases in prevalence and severity of allergic diseases, then the effect of climate change on public health in Bavaria may be significant.

Variability in the Betula pollen concentrations in the atmosphere of six urban areas in Slovakia in 2018

Betula pollen is one of the most important aeroallergens during the spring months in the central European countries. In 2018, pollen monitoring was conducted in six urban areas (Bratislava, Banská Bystrica, Košice, Nitra, Trnava, and Žilina) in Slovakia. Investigations were carried out using a volumetric Hirst-type pollen trap (Burkard). Betula pollen season timing was determined by the 90% method when the start and end of the season were defined as the date when 5% and 95%, respectively of the total pollen sum was reached. The pollen season start date was recorded earliest in Bratislava (April 8th) and latest in Banská Bystrica (April 12th). The highest both seasonal total pollen concentration (7,390 P/m3) and birch pollen allergen risk were found in Banská Bystrica. The shortest pollen season was recorded in Žilina (13 days) and the longest in Košice (25 days). Peak daily pollen concentrations ranged between 1,567 P/m3 in Žilina and 202 P/m3 in Košice.

Analysis of Corylus pollen season in Poland in 2020

In Poland hazel is one of the earliest flowering plants and in phenology it belongs to indicator plants that mark the beginning of early spring. Hazel pollen grains contain allergens that are a cause of pollen allergy during the early spring period. The aim of the present study was to compare Corylus pollen seasons in 2020 in the following 11 cities located in different regions of Poland: Szczecin, Bydgoszcz, Zielona Gora, Wroclaw, Opole, Sosnowiec, Piotrkow Trybunalski, Warsaw, Lublin, Olsztyn, and Bialystok. This research was conducted using the volumetric method and Burkard or Lanzoni pollen samplers. Pollen season duration was determined by the 95% method. This study analyzed the specific parameters of the pollen season (start, end, peak value, peak date, annual total) and also determined the number of days with a concentration exceeding the threshold values at which the first allergy symptoms in people sensitized to hazel pollen and symptoms in all allergic patients occur, respectively. The hazel pollen season in 2020 began relatively early, between January 11th and February 2nd. The season start was recorded earliest in Opole and latest in Olsztyn and Bialystok. The study found that the pollen season started earlier in the western part of Poland than in the eastern regions. The highest maximum Corylus pollen concentration was recorded in Lublin (388 P/m3), whereas the lowest one in Bydgoszcz (48 P/m3). The maximum daily concentration of Corylus pollen grains was recorded in different periods in the individual cities, while the peak concentration values occurred between January 31th and March 4th. The highest risk of allergy in people sensitive to the pollen of this taxon was found in Lublin since the most days with a pollen concentration exceeding the threshold value were observed in this city. Lublin was found to have the highest annual total values and they were 1.6–5.6 times higher than in the other cities. The highest annual pollen sums and peak values as well as the highest number of days with a concentration exceeding the threshold value had also been recorded in Lublin previously.

Grass pollen season in selected cities of Poland in 2019

The pollen of grass is the primary trigger of pollen allergies during the summer months. It causes some of the most severe and difficult-to-treat symptoms. During the flowering of grass, over 90% of patients allergic to grass pollen suffer from allergic conditions. The symptoms caused by grass pollen allergens appear in some patients after exceeding the concentration of 20 grains in m3 of air. The aim of this study was to compare Poaceae pollen seasons in 2019 in 11 cities located in different regions of Poland. Pollen monitoring was conducted in Bialystok, Bydgoszcz, Sosnowiec, Lublin, Olsztyn, Szczecin, Piotrkow Trybunalski, Warsaw, Opole, Zielona Gora and Wroclaw. Airborne pollen was monitored by the volumetric method using Burkard or Lanzoni pollen samplers. Pollen season length was determined by the 98% method, where the start of the season was defined as the date when 1% of the seasonal pollen total was trapped and the end of the season as the date, when 99% of the seasonal pollen total was reached.The pollen season start date was recorded earliest in Zielona Gora (April 27th), latest in Szczecin (May 25th). The highest grass pollen concentration values were found in Lublin, Piotrkow Trybunalski and Warsaw, whereas the lowest ones in Bialystok. The annual grass pollen sum was highest in Lublin (4715 pollen grains), whereas it was lowest in Bialystok (1256 pollen grains). A relatively high pollen count was also recorded in Warsaw (4106 pollen grains) and Zielona Gora (4077 pollen grains). The longest grass pollination season was recorded in Zielona Gora (139 days) and the shortest in Szczecin (110 days). In the remaining measuring points, grass pollen in the air maintained from 112 to 131 days. The highest grass pollen allergen risk occurred in Lublin, Olsztyn and Zielona Gora and the lowest in Bialystok.

The analysis of Betula pollen season in Poland in 2019

The aim of this study was to compare Betula pollen seasons in 2019 in 12 cities located in different regions of Poland. Pollen monitoring was conducted in Bialystok, Bydgoszcz, Cracow, Lublin, Olsztyn, Opole, Piotrkow Trybunalski, Sosnowiec, Szczecin, Warsaw, Wroclaw, and Zielona Gora. Airborne pollen was monitored by the volumetric method using Burkard or Lanzoni pollen samplers. Pollen season length was determined by the 98% method. The pollen season start date was recorded earliest in Wroclaw and Zielona Gora, and latest in Bialystok. The highest Betulapollen concentration values were found in Lublin, whereas the lowest ones in Bialystok. In most of the cities, the maximum daily Betula pollen concentration was recorded on April 19th or 20th. Exceptionally, in Wroclaw the peak value occurred on April 8th, while in Bialystok as late as April 29th. The annual pollen sum reached the highest values in Warsaw and the lowest ones in Bialystok. The highest risk of allergy in people sensitive to the pollen of this taxon was found in Bydgoszcz, Zielona Gora, Szczecin, Opole, and Warsaw

Temporal trends in airborne pollen seasonality: evidence from the Italian POLLnet network data

Airborne pollen reflects local vegetative composition and is a proxy for flowering phase. Long-term pollen data might reflect changes in biodiversity and phenology, attributable also to the effect of climate change. The present study, based on pollen data collected within the Italian aerobiological network POLLnet, aimed to verify whether there is any evidence of temporal changes in pollen season timing and its relation with meteorological variables. To this purpose, nine stations located in North and Central Italy were selected, and twelve pollen taxa, both arboreal and herbaceous, were considered. For each taxon and station, 11–17-year datasets of airborne pollen concentration within the period 2000–2016 were analysed. Four different pollen season descriptors were elaborated (start, end and peak date, season length) and analysed their temporal trend, also in relation to temperature and precipitation. Overall, the results showed a negative temporal trend in pollen season starting date, which indicates a tendency towards an earlier flowering for Corylus, Quercus, Gramineae and Urticaceae in all stations (even if statistically significant in six out of 36 cases). The effect of meteorological parameters was evidenced by negative correlations between pollen season starting date and temperature. With the exception of Olea, Ambrosia and Artemisia, all the remaining pollen taxa showed significant (negative) correlations between pollen season start date and average temperature of the previous months in at least half of the stations. As for precipitation, no relevant correlations were detected with pollen season parameters. The results are also interpreted considering the different biogeographic areas in which the nine stations are located. Long-term pollen dataset is useful in phenological studies and for the detection of climate change effects.

Spatio-temporal monitoring and modelling of birch pollen levels in Belgium

In Belgium, ~ 10% of the people is estimated to suffer from allergies due to pollen emitted by the birch family trees. Timely information on forthcoming pollen exposure episodes using a forecasting system can allow patients to take preventive measures. To date, the only available information on pollen concentrations in Belgium comes from five stations that monitor daily airborne birch pollen concentrations, but real-time and detailed spatial information is lacking. Pollen transport models can both quantify and forecast the spatial and temporal distribution of airborne birch pollen concentrations if accurate and updated maps of birch pollen emission sources are available and if the large inter-seasonal variability of birch pollen is considered. Here we show that the SILAM model driven by ECMWF ERA5 meteorological data is able to determine airborne birch pollen levels using updated maps of areal fractions of birch trees, as compared to the pollen observations of the monitoring stations in Belgium. Forest inventory data of the Flemish and Walloon regions were used to update the default MACCIII birch map. Spaceborne MODIS vegetation activity combined with an updated birch fraction map and updated start and end dates of the birch pollen season were integrated into SILAM. The correlation (R2) between SILAM modelled and observed time series of daily birch pollen levels of 50 birch pollen seasons increased up to ~ 50%. The slopes of the linear correlation increased on average with ~ 60%. Finally, SILAM is able to capture the threshold of 80 pollen grains m−3 exposure from the observations.

Pollen calendars and maps of allergenic pollen in North America

Pollen is a common allergen that causes significant health and financial impacts on up to a third of the population of the USA. Knowledge of the main pollen season can improve diagnosis and treatment of allergic diseases. Our objective in this study is to provide clear, quantitative visualizations of pollen data and make information accessible to many disciplines, in particular to allergy sufferers and those in the health field. We use data from 31 National Allergy Bureau (NAB) pollen stations in the continental USA and Canada from 2003 to 2017 to produce pollen calendars. We present pollen season metrics relevant to health and describe main pollen season start and end dates, durations, and annual pollen integrals for specific pollen taxa. In most locations, a small number of taxa constitute the bulk of the total pollen concentration. Start dates for tree and grass pollen season depend strongly on latitude, with earlier start dates at lower latitudes. Season duration is correlated with the start dates, such that locations with earlier start dates have a longer season. NAB pollen data have limited spatiotemporal coverage. Increased spatiotemporal monitoring will improve analysis and understanding of factors that govern airborne pollen concentrations.