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 describe

Human plague: An old scourge that needs new answers

Yersinia pestis, the bacterial causative agent of plague, remains an important threat to human health. Plague is a rodent-borne disease that has historically shown an outstanding ability to colonize and persist across different species, habitats, and environments while provoking sporadic cases, outbreaks, and deadly global epidemics among humans. Between September and November 2017, an outbreak of urban pneumonic plague was declared in Madagascar, which refocused the attention of the scientific community on this ancient human scourge. Given recent trends and plague’s resilience to control in the wild, its high fatality rate in humans without early treatment, and its capacity to disrupt social and healthcare systems, human plague should be considered as a neglected threat. A workshop was held in Paris in July 2018 to review current knowledge about plague and to identify the scientific research priorities to eradicate plague as a human threat. It was concluded that an urgent commitment is needed to develop and fund a strong research agenda aiming to fill the current knowledge gaps structured around 4 main axes: (i) an improved understanding of the ecological interactions among the reservoir, vector, pathogen, and environment; (ii) human and societal responses; (iii) improved diagnostic tools and case management; and (iv) vaccine development. These axes should be cross-cutting, translational, and focused on delivering context-specific strategies. Results of this research should feed a global control and prevention strategy within a “One Health” approach

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 50m 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 10m AGL). We show that pollen concentrations measured at >10m are representative for background near-ground levels

Atmospheric transport reveals grass pollen dispersion distances

Identifying the origin of bioaerosols is of central importance in many biological disciplines, such as human health, agriculture, forestry, aerobiology and conservation. Modelling sources, transportation pathways and sinks can reveal how bioaerosols vary in the atmosphere and their environmental impact. Grass pollen are particularly important due to their widely distributed source areas, relatively high abundance in the atmosphere and high allergenicity. Currently, studies are uncertain regarding sampler representability between distance and sources for grass pollen. Using generalized linear modelling, this study aimed to analyse this relationship further by answering the question of distance-to-source area contribution. Grass pollen concentrations were compared between urban and rural locations, located 6.4 km apart, during two years in Worcestershire, UK. We isolated and refined vegetation areas at 100 m × 100 m using the 2017 CEH Crop Map and conducted atmospheric modelling using HYSPLIT to identify which source areas could contribute pollen. Pollen concentrations were then modelled with source areas and meteorology using generalized linear mixed-models with three temporal variables as random variation. We found that the Seasonal Pollen Integral for grass pollen varied between both years and location, with the urban location having higher levels. Day of year showed higher temporal variation than the diurnal or annual variables. For the urban location, grass source areas within 30 km had positive significant effects in predicting grass pollen concentrations, while source areas within 2–10 km were important for the rural one. The source area differential was likely influenced by an urban-rural gradient that caused differences in the source area contribution. Temperature had positive highly significant effects on both locations while precipitation affected only the rural location. Combining atmospheric modelling, vegetation source maps and generalized linear modelling was found to be a highly accurate tool to identify transportation pathways of bioaerosols in landscape environments

Sentinel-2 satellite and HYSPLIT model suggest that local cereal harvesting substantially contribute to peak Alternaria spore concentrations

Alternaria is a human/animal allergen and plant/animal pathogen. Cereal harvesting emits a large amount of Alternaria spores into the atmosphere. However, estimating the peak spore periods and source areas from large areas is often a challenge because of insufficient observation stations. The purpose of this study was to examine, using remote sensing and an atmospheric transport and dispersion model, the contribution of cereal harvesting to peak Alternaria spore concentrations. Daily Alternaria spores were collected using Hirst-type traps in 12 sites in Europe for the period 2016-2018. Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) back-trajectory and dispersion model was integrated with Sentinel-2 satellite imagery, Corine Land Cover 2018 (CLC2018) and Eurostat cereal data 2016 to map the Alternaria spore peaks and source areas in the 12 sites. Ground truth harvest data, collected at Worcester, UK, in 2018, and meteorological data were used to determine any effect of cereal harvesting and weather on peak spore concentrations. The results showed that the Sentinel-2 satellite detected agricultural areas that underwent intensive harvesting and this coincided with a rapid increase of Alternaria spore concentrations. Furthermore, local agricultural areas cultivated with cereals were the main sources of the peak Alternaria spore concentrations in all the study sites. Remote agricultural and non-agricultural sources, to a lesser extent, contributed to the peak spore concentrations at some sites, e.g. Borstel, Leicester and Worcester. Temperature during the harvesting periods (July and August) was found to significantly contribute to the peak spore concentrations. Overall, the study showed that it is possible to use Sentinel-2 satellite data alongside atmospheric transport and dispersion models to estimate periods of peak Alternaria spore concentrations and sources at a continental scale. This approach can be replicated for other bioaerosols that affect human health, agriculture and forestry

Sentinel-2 satellite shows that local cereal harvesting substantially contributes to peak Alternaria spore concentrations in Central-Northern Europe

Alternaria is a plant and animal pathogen and human aeroallergen. Cereal harvesting emits large amount of Alternaria spores into the atmosphere. However, estimating the peak spore periods from large areas is often a challenge because of insufficient observation stations. The purpose of this study was to examine, using remote sensing, the contribution of cereal harvesting to peak Alternaria spore concentrations for the period 2016-2018. Sentinel-2 satellite imagery alongside corine land cover 2018 (CLC2018) and Eurostat data on cereal production were integrated to map the potential sources contributing to the peak of Alternaria spore concentrations at 12 central-northern European sites. Ground truth cereal harvesting at Worcester and meteorological data for all sites were examined for their effect on daily Alternaria spore concentrations. Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) backward trajectory and dispersion modelling was used to simulate the dispersion and deposition of the spores from the air masses. The results showed that minimum NDVI values of agricultural areas were detected at a time when intensive harvesting happened and this coincided with a rapid increase of Alternaria spore concentrations. Furthermore, local agricultural areas cultivated with cereals were the main sources of the peak Alternaria spore concentrations in all the study sites. Remote sources also potentially contributed to the peak Alternaria spore concentrations. Natural sources, e.g. pastures, grasslands and green urban areas, to a lesser extent, also contributed to the peak spore concentrations at some sites, e.g. Borstel, Leicester and Worcester. Temperature and precipitation during the harvesting periods (Jul and Aug) were found to significantly contribute to the peak spore concentrations. Overall, the study showed that it is possible to estimate periods of peak Alternaria spore concentrations over large areas using Sentinel-2 satellites. This approach can be replicated for other bioaerosols that affect health, agriculture and forestry

Effect of Height on Pollen Sampling in Relation to Pollen Exposure at Ground Level

Pollen monitoring networks around the world are mainly based on rooftop-located stations on buildings. Thus, measured airborne pollen levels could be different from ground level, where most allergic individual reside. Until now, the effects of height of sampling on pollen concentration are not well documented. The aim of this meta-analysis was to analyse these effects using a large number of twin sampling stations. Pollen data from 45 twin-stations Hirst-type volumetric spore traps were analyzed, with a maximum distance of 5km between the twin traps, from 25 different locations. To compare the effect of height, the mean of the daily ratio of the amounts of pollen registrered at different heights was used. The values of the lowest station were divided by the higher station. Stations between 1.5m and 50 agl were considered. The results showed that the traps at lower height registered generally higher pollen concentration (average pollen ratio higher than 1), although the behaviour of the ratio differed per pollen type. For instance, both Poaceae and Betula showed that as the height differenc eincreased, the pollen ratio was higher up to a certain height difference when the ratio stabilizes (around 1.5). On the other hand, the standard deviation of the pollen ratio was greater for the traps closer to ground level. Therefore the height difference is a factor which explains the pollen ratio in conjunction with other variables such as the minimum height of the lower trap or the distance between the spore traps. These findings are highly relevant to clinical practice, as the relationship between pollen exposure at ground level and monitored airborne pollen concentrations at roof-top elvel are determined. Thus, the optimal pollen monitoring height could be optimized based on these result

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