Cluster Analysis of Variations in the Diurnal Pattern of Grass Pollen Concentrations in Northern Europe (Copenhagen) and Southern Europe (Córdoba)

From an allergological point of view, Poaceae pollen is one of the most important type of pollen that the population is exposed to in the ambient environment. There are several studies on intra diurnal patterns in grass pollen concentrations, and agreement on the high variability. However, the method for analysing the different patterns is not yet well established. The aim of the present study is therefore to examine the method of pattern analysis by statistical clustering, as well as relating the proposed patterns to time of season and meteorological variables at two highly different biogeographical locations; Córdoba, Spain and Copenhagen, Denmark. Airborne pollen is collected by Hirst type volumetric spore traps and counted using an optical microscope at both sites. The counts were converted to two-hours concentrations and a new method based on cluster analysis was applied with the aim of determining the most frequent diurnal patterns in pollen concentrations and their dependencies of site, season and meteorological variables. Three different well defined diurnal patterns were identified at both locations. The most frequent pattern in Copenhagen was associated with days having peak pollen concentrations in the evening (maximum between18h-20h), whereas the most frequent pattern at Córdoba was associated with days having peak pollen concentrations in the afternoon (maximum between 14h-16h). These three patterns account for 70% of days with no rain and pollen concentrations above 20 grains m-3. The most frequent pattern accounts for 40% and 57% of the days in Córdoba and Copenhagen respectively. The analysis clearly shows the great variation in pollen concentration pattern, albeit a dominating pattern can be found. It was not possible to explain all the differences in the patterns by the meteorological variables when examined individual. Clustering method is estimated to be an appropriate methodology for studying aerobiological phenomena with high variability

Identifying Urban Sources as Cause of Elevated Grass Pollen Concentrations using GIS and Remote Sensing

We examine here the hypothesis that during flowering, the grass pollen concentrations at a specific site reflect the distribution of grass pollen sources within a few kilometres of this site.We perform this analysis on data from a measurement campaign in the city of Aarhus (Denmark) using three pollen traps and by comparing these observations with a novel inventory of grass pollen sources. The source inventory is based on a new methodology developed for urbanscale grass pollen sources. The new methodology is believed to be generally applicable for the European area, as it relies on commonly available remote sensing data combined with management information for local grass areas. The inventory has identified a number of grass pollen source areas present within the city domain. The comparison of the measured pollen concentrations with the inventory shows that the atmospheric concentrations of grass pollen in the urban zone reflect the source areas identified in the inventory, and that the pollen sources that are found to affect the pollen levels are located near or within the city domain. The results also show that during days with peak levels of pollen concentrations there is no correlation between the three urban traps and an operational trap located just 60 km away. This finding suggests that during intense flowering, the grass pollen concentration mirrors the local source distribution and is thus a local-scale phenomenon. Model simulations aimed at assessing population exposure to pollen levels are therefore recommended to take into account both local sources and local atmospheric transport, and not to rely only on describing regional to long-range transport of pollen. The derived pollen source inventory can be entered into local-scale atmospheric transport models in combination with other components that simulate pollen release in order to calculate urban-scale variations in the grass pollen load. The gridded inventory with a resolution of 14m is therefore made available as supplementary material to this paper, and the verifying grass pollen observations are additionally available in tabular form

Stor variation i græspollen er en udfordring i vejledningen til allergikere - resultater fra ny dansk pollenforskning "Large variations in grass pollen concentrations are a challenge in the guidance of hayfever patients – new results from Danish research”

Pollenallergi rammer op mod en femtedel af Danmarks befolkning og forringer deres hverdag og livskvalitet. Et af de vigtigste værktøjer,en pollenallergiker har, er information om, hvornår der er pollen i luften. Denne information anvender allergikere til at planlægge indtag af medicin og tilrettelæggelse af hverdagen. Således kan de begrænse deres symptomer så meget som muligt. En primær kilde tilinformation er pollenmålinger fra Viborg og København. Ny forskning fra Aarhus Universitet (AU) og Astma Allergi Danmark afdækker, at der er væsentlige lokale forskelle I mængden af græspollen. Denne variation gælder især for dage med høje pollental. Resultaterne indikerer, at særligt på dage med høje pollental for græs er nærheden til locale kilder meget vigtig. På samme tid er de lokale koncentrationer ikke nødvendigvis korreleret med pollenmålinger fra de nationale målestationer i Viborg og København.Information om døgnvariationen i pollen er vigtig for pollenallergikerne. De nye studier indikerer store forskelle fra dag til dag, I forhold til hvornår de højeste koncentrationer forekommer, og at dette billede ændrer sig over pollensæsonen. Viden om døgnvariation, og hvad der styrer den, er endnu langt fra fyldestgørende i forhold til at kunne formidle denne information til pollenallergikere. Vores studier peger i retning af, at de højeste koncentrationer af græspollen hyppigst forekommer tidligt på aftenen, men at de kan forekomme på alle tider af døgnet

Seasonal Variation in Diurnal Atmospheric Grass Pollen Concentration Profiles

In this study, the diurnal atmospheric grass pollen concentration profile within the Danish city of Aarhus was shown to change in a systematic manner as the pollen season progressed. Although diurnal grass pollen profiles can differ greatly from day-to-day, it is common practice to establish the time of day when peak concentrations are most likely to occur using seasonally averaged diurnal profiles. Atmospheric pollen loads are highly dependent upon emissions, and different species of grass are known to flower and emit pollen at different times of the day and during different periods of the pollen season. Pollen concentrations are also influenced by meteorological factors – directly through those parameters that govern pollen dispersion and transport, and indirectly through the weather-driven flowering process. We found that three different profiles dominated the grass pollen season in Aarhus – a twin peak profile during the early season, a single evening profile during the middle of the season, and a single midday peak during the late season. Whilst this variation could not be explained by meteorological factors, no inconsistencies were found with the theory that it was driven by a succession of different grass species with different diurnal flowering patterns dominating atmospheric pollen loads as the season progressed. The potential for exposure was found to be significantly greater during the late-season period than during either the early- or mid-season periods

An Assesment of the Potential for Co-exposure to Allergenic Pollen and Air Pollution in Copenhagen, Denmark

Background.Co-exposure to air pollutants and allergenic pollen can elicit or exacerbate a number of conditions in susceptible individuals, including allergic airway diseases. Both concentrations and diurnal patterns are relevant when assessing potential health effects. Methods.To assess which pollutants may be of particular relevance when investigating co-exposure with pollen, we examined yearly variation and diurnal patterns of pollutants on days with high pollen levels, and also for the remaining part of the pollen season. This analysis included measurements of grass and birch pollen, sulphur dioxide (SO2), ozone (O3), nitrogen dioxide (NO2) and particulate matter (PM) in the period 1997-2012. Results.O3 concentrations were found to be higher on peak pollen days and high O3 concentrations coincide both seasonally and diurnally with high pollen counts, potentially leading to clinically relevant simultaneous co-exposure. NO2 and SO2 did not appear to coincide in concentration peaks with pollen counts, and concentrations were well below potential thresholds for adjuvant effects to the allergic reaction. Neither diurnal nor seasonal concentration peaks in PM were found to coincide with peaks in pollen concentrations, however daily average PM concentrations were higher on peak pollen days than on non-peak days. Conclusion. This study indicates that when considering co-exposure effects from pollen and pollutants, O3 appears to be the most relevant pollutant to further examine for clinical effects of simultaneous co-exposures