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According to WHO, by 2050, at least one person out of two will suffer from an allergy disorder resulting from the accelerating air pollution associated with toxic gas emissions and climate change. Airborne pollen, and associated allergies, are major public health topics during the pollination season, and their effects are further strengthened due to climate change. Therefore, assessing the airborne pollen allergy risk is essential for improving public health. This study presents a new computational fluid dynamics methodology for risk assessment of local airborne pollen transport in an urban environment. Specifically, we investigate the local airborne pollen transport from trees on a university campus in the north of France. We produce risk assessment maps for pollen allergy for five consecutive days during the pollination season. The proposed methodology could be extended to larger built-up areas for different weather conditions. The risk assessment maps may also be integrated with smart devices, thus leading to decision-aid tools to better guide and protect the public against airborne pollen allergy.

From anther dehiscence to its atmospheric journey, airborne pollen grains can come into contact with other particulate matter (PM) and the external wall of pollen grains can be polluted by adhered atmospheric particles. Pollen and PM are some of the most common asthma triggers. The aim of this review was to discuss literature reporting pollen–particle complexes in the outdoor environment so their potential role in enhancing the risk of allergy could be examined. Twenty-five studies report pollen–particle complexes observed in outdoor conditions. PM adhesion onto the pollen surface was investigated in the literature by three different experimental approaches: direct collection from anthers, bulk exposure of pollen to PM in polluted areas, and direct sampling of airborne pollen during pollination. Four processes are proposed to explain deposition of PM on the surface of pollen grains: sticking of particles to anthers and pollen during dehiscence, airborne pollen-particles coagulation, wet and dry scavenging of pollen and particles, and co-deposition of PM and pollen in the respiratory system. Despite potential adverse health effects, the magnitude of pollution of pollen by PM is poorly understood. To address this issue, we suggest the following guidelines for research: (1) Possible artifacts during sampling and handling of anthers must be carefully avoided; (2) Control pollen grains (i.e. non-polluted) should be carefully selected; (3) A better knowledge of pollen atmospheric deposition and resuspension is needed; (4) The health effects of pollen-particles complexes need more attention regarding symptoms and allergic sensitization; (5) Use of individual pollen samplers could give a depiction of the degree of pollution of pollen that is actually inhaled.

This review summarizes the available data related to the effects of air pollution on pollen grains from different plant species. Several studies carried out either on in situ harvested pollen or on pollen exposed in different places more or less polluted are presented and discussed. The different experimental procedures used to monitor the impact of pollution on pollen grains and on various produced external or internal subparticles are listed. Physicochemical and biological effects of artificial pollution (gaseous and particulate) on pollen from different plants, in different laboratory conditions, are considered. The effects of polluted pollen grains, subparticles, and derived aeroallergens in animal models, in in vitro cell culture, on healthy human and allergic patients are described. Combined effects of atmospheric pollutants and pollen grains-derived biological material on allergic population are specifically discussed. Within the notion of “polluen,” some methodological biases are underlined and research tracks in this field are proposed.

The multiwavelength Mie–Raman–fluorescence lidar of the University of Lille has the capability to measure three aerosol backscattering coefficients, two extinction coefficients and three linear depolarization ratios, together with fluorescence backscattering at 466 nm. It was used to characterize aerosols during the pollen season in the north of France for the period March–June 2020. The results of observations demonstrate that the presence of pollen grains in aerosol mixture leads to an increase in the depolarization ratio. Moreover, the depolarization ratio exhibits a strong spectral dependence increasing with wavelength, which is expected for the mixture containing fine background aerosols with low depolarization and strongly depolarizing pollen grains. A high depolarization ratio correlates with the enhancement of the fluorescence backscattering, corroborating the presence of pollen grains. Obtained results demonstrate that simultaneous measurements of particle depolarization and fluorescence allows for the separation of dust, smoke particles and aerosol mixtures containing the pollen grains.

Birch is the most allergenic tree species in Northern and Central Europe. Airborne birch pollen concentrations are observed to be on the rise for several decades. Health hazard due to birch pollen grains (BPGs) can worsen due to particulate air pollution. The prevalence of the intimate mixture of BPGs with atmospheric particulate matter (APM) at the single pollen grain level is still unraveled. In this study, APM transfer mechanisms to birch catkins and BPGs prior to pollination were investigated at an urban-industrial and a peri-urban site in Northern France. The surface of catkins was heavily polluted with micrometer-sized particles. Conversely, BPGs were relatively unpolluted with on average 0.1 particle.BPG −1 . Differences in the chemical composition of adhered particles were observed as a function of the sampling sites. In contrast, no significant difference was found in terms of surface concentrations of APM adhered to BPGs and catkins between the two sites. Comparison of the number of particles deposited per pollen grain according to whether they were harvested from catkins or collected while airborne suggests that particulate pollution of pollen occurs preferentially after pollen shedding, either by impaction or coagulation mechanisms with other suspended APM or by pollen settling on dust-contaminated surfaces followed by resuspension.

The lipid fraction of birch pollen grains (BPGs) is not yet fully described, although pollen lipid molecules may play a role in the allergic immune response. The mechanisms by which atmospheric pollutants modify allergenic pollen grains (PGs) are also far from being elucidated despite high potential effects on allergic sensitization. This work is a contribution to a better description of the lipid profile (both external and cytoplasmic) of BPGs and of alterations induced by gaseous air pollutants. Several lipid extractions were performed using organic and aqueous solvents on BPGs following exposure to ozone and/or nitrogen dioxide and under conditions favoring the release of internal lipids. Ozone reacted with alkenes to produce aldehydes and saturated fatty acids, while nitrogen dioxide was shown to be unreactive with lipids. NO 2 exhibited a protective effect against the reactivity of alkenes with ozone, probably by competition for adsorption sites. The decreased reactivity of ozone during simultaneous exposure to NO 2 /O 3 raised the possibility of a Langmuir-Hinshelwood mechanism. Oxidation reactions induced by exposure of BPGs to ozone did not substantially modify the extraction of lipids by aqueous solvent, suggesting that the bioaccessibility of lipids was not modified by oxidation. On the contrary, the rupture of PGs appeared to be a key factor in enhancing the bioaccessibility of bioactive lipid mediators (linoleic and α-linolenic acids) in an aqueous solution. The internal lipid fraction of BPGs has specific characteristics compared with external lipids, with more abundant hexadecanoic acid, tricosanol, and particularly unsaturated fatty acids (linoleic and α-linolenic acids). Several mechanisms of action of gaseous pollutants on allergenic pollen were identified in this study: gaseous air pollutants can (i) modify the external lipid fraction by reactivity of alkenes, (ii) adsorb on the surface of PGs and be a source of oxidative stress after inhalation of PGs, and (iii) promote the release of cytoplasmic bioactive lipids by facilitating pollen rupture.

The advent of automatic pollen and fungal spore monitoring over the past few years has brought about a paradigm change. The provision of real-time information at high temporal resolution opens the door to a wide range of improvements in terms of the products and services made available to a widening range of end-users and stakeholders. As technology and methods mature, it is essential to properly quantify the impact automatic monitoring has on the different end-user domains to better understand the real long-term benefits to society. In this paper, we focus the main domains where such impacts are expected, using Europe as a basis to provide qualitative estimates and to describe research needs to better quantify impacts in future. This will, in part, also serve to justify further investment and help to expand monitoring networks.

The dataset presents a 43 year-long reanalysis of pollen seasons for three major allergenic genera of trees in Europe: alder (Alnus), birch (Betula), and olive (Olea). Driven by the meteorological reanalysis ERA5, the atmospheric composition model SILAM predicted the flowering period and calculated the Europe-wide dispersion pattern of pollen for the years 1980–2022. The model applied an extended 4-dimensional variational data assimilation of in-situ observations of aerobiological networks in 34 European countries to reproduce the inter-annual variability and trends of pollen production and distribution. The control variable of the assimilation procedure was the total pollen release during each flowering season, implemented as an annual correction factor to the mean pollen production. The dataset was designed as an input to studies on climate-induced and anthropogenically driven changes in the European vegetation, biodiversity monitoring, bioaerosol modelling and assessment, as well as, in combination with intra-seasonal observations, for health-related applications.

Grass pollen grains are an important source of aeroallergens eliciting respiratory allergic diseases worldwide. In the field of allergology, Phleum pratense pollen is considered as a model for other grass taxa. Upon contact with the aqueous phase of mucosa membranes, lipids are co-delivered from pollen grains with allergens. Lipid molecular species have pro-allergic, pro-inflammatory and immunomodulatory effects on the cells of the allergic immune response. The quantitative analysis of Phleum pratense pollen lipids is missing in the literature. In this work, the total mass of lipids extractable by methylene chloride was determined to be 22 ± 1 µg per mg of Phleum pratense pollen. Eighteen percent of the lipidic mass was quantified and identified by gas chromatographic analysis. Identified lipids included alkanes, alkenes, saturated and unsaturated fatty acids, aldehydes and alcohols. Pollen samples harvested at different times and locations showed a very similar lipidic pattern, both qualitatively and quantitatively. Laboratory ozone exposure of pollen substantially modified its lipidic composition by reactions of ozone with alkenes leading to the production of fatty acids and aldehydes. A deeper knowledge of the lipids released by pollen grains, including pollen from polluted areas, is essential for a better understanding of the chemical environment at the cellular level where allergic reactions take place.