Co-exposure to highly allergenic airborne pollen and fungal spores in Europe.

The study is aimed at determining the potential spatiotemporal risk of the co-occurrence of airborne pollen and fungal spores high concentrations in different bio-climatic zones in Europe. Birch, grass, mugwort, ragweed, olive pollen and Alternaria and Cladosporium fungal spores were investigated at 16 sites in Europe, in 2005-2019. In Central and northern Europe, pollen and fungal spore seasons mainly overlap in June and July, while in South Europe, the highest pollen concentrations occur frequently outside of the spore seasons. In the coldest climate, no allergy thresholds were exceeded simultaneously by two spore or pollen taxa, while in the warmest climate most of the days with at least two pollen taxa exceeding threshold values were observed. The annual air temperature amplitude seems to be the main bioclimatic factor influencing the accumulation of days in which Alternaria and Cladosporium spores simultaneously exceed allergy thresholds. The phenomenon of co-occurrence of airborne allergen concentrations gets increasingly common in Europe and is proposed to be present on other continents, especially in temperate climate.

Outdoor airborne allergens: Characterization, behavior and monitoring in Europe.

Aeroallergens or inhalant allergens, are proteins dispersed through the air and have the potential to induce allergic conditions such as rhinitis, conjunctivitis, and asthma. Outdoor aeroallergens are found predominantly in pollen grains and fungal spores, which are allergen carriers. Aeroallergens from pollen and fungi have seasonal emission patterns that correlate with plant pollination and fungal sporulation and are strongly associated with atmospheric weather conditions. They are released when allergen carriers come in contact with the respiratory system, e.g. the nasal mucosa. In addition, due to the rupture of allergen carriers, airborne allergen molecules may be released directly into the air in the form of micronic and submicronic particles (cytoplasmic debris, cell wall fragments, droplets etc.) or adhered onto other airborne particulate matter. Therefore, aeroallergen detection strategies must consider, in addition to the allergen carriers, the allergen molecules themselves. This review article aims to present the current knowledge on inhalant allergens in the outdoor environment, their structure, localization, and factors affecting their production, transformation, release or degradation. In addition, methods for collecting and quantifying aeroallergens are listed and thoroughly discussed. Finally, the knowledge gaps, challenges and implications associated with aeroallergen analysis are described.

Atmospheric pollen allergen load and environmental patterns in central and southwestern Iberian Peninsula.

Over one quarter of the population in industrialised countries suffers from some type of allergy and inhaled aeroallergens from pollen are the primary cause of allergic ailments. The networks for monitoring biological air quality measure the airborne pollen concentrations that characterize periods of exposure to major airborne aeroallergens but there are certain discrepancies in relation to the allergen-pollen dynamic. In this paper we analyse the airborne allergens Ole e 1, Phl p 1, Phl p 5 and Pla a 1, and interpreted the adjustments and mismatches in their concentrations in relation to airborne pollen. The influence of main environmental patterns was considered. The study was conducted in two urban areas of the centre and southwest of the Iberian Peninsula (Toledo in Spain and Évora in Portugal). Monitoring for pollen followed the standard protocol using Hirst volumetric spore traps and allergenic particles were quantified by ELISA assay. The results indicate that the discrepancies in this relationship were affected by the weather conditions up to 6 days prior. Precipitation and humidity above normal values caused a higher concentration of the allergen Pla a 1. This effect occurred in reverse in the case of humidity for the allergens Ole e 1 and Phl p 1. Humidity and precipitation generated the same pattern in the allergen-pollen relationship in both Phl p 1 and Phl p 5. Our findings show consistent results that allow to interpret the rate of discrepancy between allergen and pollen, and it can be used to improve allergy risk prediction models generated from atmospheric pollen.

Causes of increased pollen exposure during Saharan-Sahel dust intrusions.

Airborne particulate matter such as mineral dust comes mainly from natural sources, and the African regions of Sahara and Sahel originate large amounts of the aerosols dispersed worldwide. There is little knowledge about the influence of dust episodes on airborne pollen concentrations, and although the centre and southeast of the Iberian Peninsula are frequently affected by dust intrusions, until now, no specific works have analysed the effect of these episodes on airborne pollen concentrations in these areas. The aims of this study were to analyse the simultaneous occurrence of airborne pollen peaks and Saharan-Sahel dust intrusions in the central and south-eastern Iberian Peninsula, and to study the weather conditions - air mass pathways and conditions of air temperature, relative humidity and atmospheric pressure - that influence the airborne pollen concentrations during dust episodes. The results showed that the rise in airborne pollen concentrations during dust episodes is apparent in inland Iberian areas, although not in coastal areas in the southeast where pollen concentrations are even observed to decrease, coinciding with prevailing easterly winds from the sea. Total pollen concentrations and specific pollen types such as Olea, Poaceae and Quercus showed an increase in the central Iberian Peninsula during dust episodes when two meteorological phenomena concur: 1) prevailing winds from extensive areas of major wind-pollinated pollen sources over a medium or short distance (mainly from western and southwestern areas); and 2) optimal meteorological conditions that favour pollen release and dispersal into the atmosphere (mainly high temperatures and subsequently low humidity in central areas). Both conditions often occur during the Saharan-Sahel dust intrusions in the centre. Maximum pollen peaks are therefore most likely to occur during dust episodes in the central Iberian Peninsula, thus dramatically increasing the risk of outbreaks of pollinosis and other respiratory diseases in the population.

Near-ground effect of height on pollen exposure.

The effect of height on pollen concentration is not well documented and little is known about the near-ground vertical profile of airborne pollen. This is important as most measuring stations are on roofs, but patient exposure is at ground level. Our study used a big data approach to estimate the near-ground vertical profile of pollen concentrations based on a global study of paired stations located at different heights. We analyzed paired sampling stations located at different heights between 1.5 and 50 m above ground level (AGL). This provided pollen data from 59 Hirst-type volumetric traps from 25 different areas, mainly in Europe, but also covering North America and Australia, resulting in about 2,000,000 daily pollen concentrations analyzed. The daily ratio of the amounts of pollen from different heights per location was used, and the values of the lower station were divided by the higher station. The lower station of paired traps recorded more pollen than the higher trap. However, while the effect of height on pollen concentration was clear, it was also limited (average ratio 1.3, range 0.7-2.2). The standard deviation of the pollen ratio was highly variable when the lower station was located close to the ground level (below 10 m AGL). We show that pollen concentrations measured at >10 m are representative for background near-ground levels.

Comprehensive analysis of different adhesives in aerobiological sampling using optical microscopy and high-throughput DNA sequencing.

The standardization and unification of the procedures to analyze and quantify the airborne pollen concentrations are very important topics. In this work, the effectiveness of the two most used adhesives in aerobiological sampling, silicone prepared with cyclohexane solvent (Silicone) and petroleum jelly (Vaseline), was compared under outdoor conditions. This comparison was carried out using the traditional method based on the identification and quantification by optical microscopy (OM) of the airborne pollen and the novel methodology by high-throughput sequencing analysis (HTS). Globally, the results from both methods of analysis (OM and HTS) showed a good agreement between the two adhesives tested regarding the abundance of the main pollen types present in the samples: Cupressaceae, Olea, Poaceae, Platanus, Quercus. We concluded that the results from both adhesives are comparable data. Furthermore, the comparisons between methodologies, OM vs. HTS, showed that both techniques can accurately identify the most abundant pollen types in the atmosphere for the studied periods, with a good agreement of their relative abundances especially when the airborne pollen diversity is low but showing some divergences as the number of pollen types increases.

Modeling pollen time series using seasonal-trend decomposition procedure based on LOESS smoothing.

Analysis of airborne pollen concentrations provides valuable information on plant phenology and is thus a useful tool in agriculture-for predicting harvests in crops such as the olive and for deciding when to apply phytosanitary treatments-as well as in medicine and the environmental sciences. Variations in airborne pollen concentrations, moreover, are indicators of changing plant life cycles. By modeling pollen time series, we can not only identify the variables influencing pollen levels but also predict future pollen concentrations. In this study, airborne pollen time series were modeled using a seasonal-trend decomposition procedure based on LOcally wEighted Scatterplot Smoothing (LOESS) smoothing (STL). The data series-daily Poaceae pollen concentrations over the period 2006-2014-was broken up into seasonal and residual (stochastic) components. The seasonal component was compared with data on Poaceae flowering phenology obtained by field sampling. Residuals were fitted to a model generated from daily temperature and rainfall values, and daily pollen concentrations, using partial least squares regression (PLSR). This method was then applied to predict daily pollen concentrations for 2014 (independent validation data) using results for the seasonal component of the time series and estimates of the residual component for the period 2006-2013. Correlation between predicted and observed values was r = 0.79 (correlation coefficient) for the pre-peak period (i.e., the period prior to the peak pollen concentration) and r = 0.63 for the post-peak period. Separate analysis of each of the components of the pollen data series enables the sources of variability to be identified more accurately than by analysis of the original non-decomposed data series, and for this reason, this procedure has proved to be a suitable technique for analyzing the main environmental factors influencing airborne pollen concentrations.

Characterisation of the airborne pollen spectrum in Guadalajara (central Spain) and estimation of the potential allergy risk.

Aerobiological research into airborne pollen diversity and seasonal variations in pollen counts has become increasingly important over recent decades due to the growing incidence of asthma, rhinitis and other pollen-related allergic conditions. Airborne pollen in Guadalajara (Castilla-La Mancha, Spain) was studied over a 6-year period (2008-2013) using a Hirst-type volumetric spore trap. The highest pollen concentrations were recorded from February to June, coinciding with the pollen season of the pollen types that most contribute to the local airborne pollen spectrum: Cupressaceae (32.2%), Quercus (15.1%), Platanus (13.2%), Olea (8.3%), Populus (7.8%) and Poaceae (7.2%). These are therefore critical months for allergy sufferers. The pollen calendar was typically Mediterranean and comprised 25 pollen types. Between January and March, Cupressaceae pollen concentrations exceeded allergy risk thresholds on 38 days. Other woody species such as Olea and Platanus have a shorter pollen season, and airborne concentrations exceeded allergy risk thresholds on around 13 days in each case. Poaceae pollen concentrations attained allergy risk levels on 26 days between May and July. Other highly allergenic pollen types included Urticaceae and Chenopodiaceae-Amaranthaceae, though these are less abundant than other pollen types in Guadalajara and did not exceed risk thresholds on more than 3 and 5 days, respectively.

Effect of land uses and wind direction on the contribution of local sources to airborne pollen.

The interpretation of airborne pollen levels in cities based on the contribution of the surrounding flora and vegetation is a useful tool to estimate airborne allergen concentrations and, consequently, to determine the allergy risk for local residents. This study examined the pollen spectrum in a city in central Spain (Guadalajara) and analysed the vegetation landscape and land uses within a radius of 20km in an attempt to identify and locate the origin of airborne pollen and to determine the effect of meteorological variables on pollen emission and dispersal. The results showed that local wind direction was largely responsible for changes in the concentrations of different airborne pollen types. The land uses contributing most to airborne pollen counts were urban green spaces, though only 0.1% of the total surface area studied, and broadleaved forest which covered 5% of the study area. These two types of land use together accounted for 70% of the airborne pollen. Crops, scrubland and pastureland, though covering 80% of the total surface area, contributed only 18.6% to the total pollen count, and this contribution mainly consisted of pollen from Olea and herbaceous plants, including Poaceae, Urticaceae and Chenopodiaceae-Amaranthaceae. Pollen from ornamental species were mainly associated with easterly (Platanus), southerly (Cupressaceae) and westerly (Cupressaceae and Platanus) winds from the areas where the city's largest parks and gardens are located. Quercus pollen was mostly transported by winds blowing in from holm-oak stands on the eastern edge of the city. The highest Populus pollen counts were associated with easterly and westerly winds blowing in from areas containing rivers and streams. The airborne pollen counts generally rose with increasing temperature, solar radiation and hours of sunlight, all of which favour pollen release. In contrast, pollen counts declined with increased relative humidity and rainfall, which hinder airborne pollen transport.

Spatiotemporal analysis of olive flowering using geostatistical techniques.

Analysis of flowering patterns in the olive (Olea europaea L.) are of considerable agricultural and ecological interest, and also provide valuable information for allergy-sufferers, enabling identification of the major sources of airborne pollen at any given moment by interpreting the aerobiological data recorded in pollen traps. The present spatiotemporal analysis of olive flowering in central Spain combined geostatistical techniques with the application of a Geographic Information Systems, and compared results for flowering intensity with airborne pollen records. The results were used to obtain continuous phenological maps which determined the pattern of the succession of the olive flowering. The results show also that, although the highest airborne olive-pollen counts were recorded during the greatest flowering intensity of the groves closest to the pollen trap, the counts recorded at the start of the pollen season were not linked to local olive groves, which had not yet begin to flower. To detect the remote sources of olive pollen several episodes of pollen recorded before the local flowering season were analysed using a HYSPLIT trajectory model and the findings showed that western, southern and southwestern winds transported pollen grains into the study area from earlier-flowering groves located outside the territory.

Airborne pollen of allergenic herb species in Toledo (Spain).

This study analysed airborne pollen counts for allergenic herb taxa in Toledo (central Spain), a major tourist city receiving over 2 million visitors per year, located in the region of Castilla-La Mancha. The taxa selected were Chenopodiaceae-Amaranthaceae, Plantago, Poaceae and Urticaceae, all of which produce allergenic pollen giving rise to serious symptoms in pollen-allergy sufferers. Aerobiological data were recorded over a 6-year period (2005 to 2010) using the sampling and analysis procedures recommended by the Spanish Aerobiology Network. The abundance and the temporal (annual, daily and intradiurnal) distribution of these pollen types were analysed, and the influence of weather-related factors on airborne pollen counts was assessed. Pollen from herbaceous species accounted for 20.9% of total airborne pollen in Toledo, the largest contributor being Poaceae, with 8.5% of the total pollen count; this family was also the leading cause of respiratory allergies. Examination of intradiurnal variation revealed three distinct distribution patterns: (1) peak daily counts for Chenopodiaceae-Amaranthaceae and Plantago were recorded during the hottest part of the day, i.e. from 1400 to 1600 hours; (2) Urticaceae displayed two peaks (1400-1600 and 2200 hours); and (3) Poaceae counts remained fairly stable throughout the day. Two main risk periods were identified for allergies: spring, with allergies caused by Urticaceae, Plantago and Poaceae pollen, and summer, due to Chenopodiaceae-Amaranthaceae pollen.

Models for forecasting airborne Cupressaceae pollen levels in central Spain.

The influence of meteorological variables on airborne Cupressaceae pollen levels in central Spain was analyzed, and prediction models based on polynomial and multiple regressions were used to predict pollen counts throughout the pollen season. The Cupressaceae pollen type was selected in view of both its abundance in the atmosphere of the central Iberian Peninsula (particularly from January to March) and its allergenic importance. Sampling was performed uninterruptedly over a 5-year period, using a Hirst volumetric sampler and the sampling method established by the Spanish Aerobiology Network. Temperature displayed the strongest (positive) correlation with Cupressaceae pollen counts. Polynomial and multiple regression analysis showed that maximum temperature was the most influential variable included in prediction models. The prediction equations obtained for the study period were reasonably satisfactory, accounting for 48% and 59% of the variation in airborne pollen levels.

Aerobiological study in east-central Iberian Peninsula: pollen diversity and dynamics for major taxa.

A study was made of airborne pollen counts in Cuenca (east-central Iberian Peninsula, Spain), using data obtained over a 3-year period (2008-2010). This is the first such study carried out in the World Heritage city of Cuenca, situated in the large region of Castilla-La Mancha. Air monitoring was performed using the sampling and analysis procedures recommended by the Spanish Aerobiology Network. Sampling commenced in mid- 2007, and provided the first recorded pollen-spectrum for the area. The greatest pollen-type diversity was recorded in spring, whilst the highest pollen counts (over 80 percent of the annual total) were observed between February and June. The lowest counts were found in September, November and December. The 10 leading taxa, in order of abundance, were: Cupressaceae, Quercus, Urticaceae, Pinus, Olea, Poaceae, Populus, Platanus, Chenopodiaceae-Amaranthaceae and Plantago. The pollen calendar was thus typically Mediterrean, and comprised the 27 pollen types reaching 10-day mean counts of over 1 grain/m(3) of air. Maximum concentration values during the day were recorded between 12:00-20:00, coinciding with the highest temperatures and lowest humidity levels. The pollen types responsible for most allergies in the city of Cuenca, ordered by the number of days on which risk levels were reached, were: Poaceae, Urticaceae, Cupressaceae, Olea, Platanus and Chenopodiaceae-Amaranthaceae.

Intradiurnal variations of allergenic tree pollen in the atmosphere of Toledo (central Spain).

To study the impact of inhaling airborne pollen on health, it is important to know not only their average daily concentrations but also the intradiurnal behaviour of these biological particles. This study reports the bi-hourly distribution of the arboreal airborne pollen types more abundant in the atmosphere of Toledo (central Spain), many of them triggering important allergic processes in Toledo citizens and tourist visitors. Knowledge of bi-hourly pattern atmospheric variation pollen may help pollinosis patients to adopt preventive measures and plan their outdoor activities accordingly. Intradiurnal variation has been studied for the arboreal pollen types: Cupressaceae, Fraxinus, Olea, Platanus, Populus, Quercus and Ulmus, during the period 2005-2008. The main hourly pollen concentrations were observed during sunlight hours and the maximum pollen values obtained at midday and in the afternoon, except for pollen types Quercus and Platanus, whose maximum pollen concentrations were obtained during the night. The statistical analyses performed to compare pollen concentration and main hourly meteorological variables proved to be significant for most of the taxa. The results show a significant and positive effect of temperature, solar radiation and wind speed on the daily variability undergone by atmospheric pollen. Relative humidity influenced in a negative way on the intradiurnal variation of pollen in the atmosphere of Toledo.

Pollen spectrum and risk of pollen allergy in central Spain.

The present work analyses the airborne pollen dynamic of the atmosphere of Toledo (central Spain), a World Heritage Site and an important tourist city receiving over 2 millions of visitors every year. The airborne pollen spectrum, the annual dynamics of the most important taxa, the influence of meteorological variables and the risk of suffering pollen allergy are analysed. Results of the present work are compared to those obtained by similar studies in nearby regions. The average annual Pollen Index is 44,632 grains, where 70-90 percent is recorded during February-May. The pollen calendar includes 29 pollen types, in order of importance; Cupressaceae (23.3 percent of the total amount of pollen grains), Quercus (21.2 percent), and Poaceae and Olea (11.5 and 11.2 percent, respectively), are the main pollen producer taxa. From an allergological viewpoint, Toledo is a high-risk locality for the residents and tourist who visit the area, with a great number of days exceeding the allergy thresholds proposed by the Spanish Aerobiological Network (REA). The types triggering most allergic processes in Toledo citizens and tourists are Cupressaceae, Platanus, Olea, Poaceae, Urticaceae and Chenopodiaceae-Amaranthaceae. Allergic risk increases in 3 main periods: winter (January-March), with the main presence of the Cupressaceae type; spring, characterized by Poaceae, Olea, Platanus and Urticaceae pollen types; and, finally, late summer (August-September), characterized by Chenopodiaceae- Amaranthaceae pollen type, which are the main cause of allergies during these months.