Assessing the Allergenic Load of Tree Species in Kharkiv, Ukraine, Based on Aerial Pollen Survey

Large cities generally provide their populations with a sufficient standard of living, which contributes to a comfortable existence; however, city living can also negatively impact the health of its inhabitants. For several decades, researchers have observed an increase in allergies and related conditions among individuals who live in large industrial cities (D’Amato 2001; Rodinkova 2013a; Melnychenko 2015; Kuchcik et al. 2016; Cariñanos et al. 2019; Chiara et al. 2021). This has led to the hypothesis that air pollution leads to decreased immunity and increased allergies (de Lira-Quezada et al. 2024; Carvajal et al. 2025), which requires additional controls and monitoring for possible pathogens such as pollen.

Long-term aeropalynological observations provide bases for the creation of pollination calendars, which highlight particularly allergenic plants (D’Amato 2001; Rodinkova 2013a; Melnychenko 2015; Cariñanos et al. 2019; Kremenska et al. 2019; Frolov and Dudar 2020; Magyar et al. 2022; ARPAE 2024; Cervigón et al. 2024). Geographic information system (GIS) technologies are now used to create 2D and some 3D maps of the zones in cities with high plant pollen production (McInnes et al. 2017; Fernández-Alvarado and Fernández-Rodríguez 2023; Austrian Pollen Information Service 2025; Krwanji et al. 2025). Such maps will allow optimization of green-space distribution in cities and selection of appropriate tree species for landscaping (Sokolenko et al. 2023). Studies of pollen dispersal strategies have allowed scientists to identify the anemophilous plant species as more hazardous (Hruska 2003; D’Amato et al. 2007; Cariñanos and Marinangeli 2021; Magyar et al. 2022). Other studies have revealed a high sensitivity of plants’ generative organs to air pollution caused by human activities, which affects pollen viability and morphology (Shvets 2011; Bessonova et al. 2013; Matiashuk and Tkachenko 2021). These observations provide a basis for using pollen to monitor toxins and mutagens in the environment. A number of studies are looking at the effects of climate change on the structure and characteristics of pollen and pollination (Alcázar et al. 2024; Ščevková et al. 2024; Venkatesan et al. 2025). The problems of standardization and regulation of the use of allergenic plants in landscaping were discussed (Cariñanos and Casares-Porcel 2011). However, there is no universally accepted classification of plant allergenicity in Ukraine and in the world (Hruska 2003; D’Amato et al. 2007; Cariñanos and Marinangeli 2021; Chiara et al. 2021; Magyar et al. 2022).

In Ukraine and elsewhere, aeropalynological research began in the 1930s and became systematic in the 1970s (Vorobets and Kalynovych 2010; Frolov and Dudar 2020), when the International Association for Aerobiology (IAA) and the World Allergy Organization (WAO) were formed and included many European countries and the United States (IAA 2025; WAO 2025). The Ukrainian cities of Vinnytsia and Zaporizhzhia have joined the European Aeroallergen Network (EAN)(Rodinkova 2002; Maleeva et al. 2018; Kremenska et al. 2019). Pollen aerobiological studies are also conducted in Kyiv and Lviv (Vorobets and Kalynovych 2010; Frolov and Dudar 2020).

Examination of a typical urban landscape indicates the presence of a significant number of trees and shrubs that can cause allergies. This problem has occurred because potential allergenicity was rarely considered when planning urban landscaping (Cariñanos and Marinangeli 2021; Katz et al. 2024). Thus, in recent decades, researchers have assessed the allergenic loads of parks or other green areas according to the species composition of plants with varying degrees of allergenicity (Hruska 2003; Cariñanos et al. 2019; Chiara et al. 2021; Nowak and Ogren 2021; Fernández-Alvarado and Fernández-Rodríguez 2023; Kabisch et al. 2024).

In Kharkiv, as in many Ukrainian cities, the majority of existing trees are approaching the end of their natural life span, which makes large-scale renewal of urban plantings inevitable in the near future. Traditionally, the selection of woody plants for landscaping in Ukraine has been guided by climatic suitability and aesthetic considerations. However, current methodological recommendations do not take into account the negative impact of biopollutants, such as allergenic pollen, on public health. Despite the global relevance of this issue, Kharkiv has remained largely unexplored from the perspective of aerobiology. Establishing baseline data on airborne pollen composition and its allergenic potential is therefore essential for informed decision making in urban landscaping.

Air monitoring was conducted from 2019 to 2025 in Kharkiv, but only PM2,5 and other nonbiological substances were measured (Bodak and Dyadechko 2020; Kharkiv Regional State Administration 2024). Thus, an assessment of the allergenic load of plants used for landscaping in Kharkiv is important and will aid in the development of a scientific basis for plant selection.

The simplest method for capturing pollen from the air on a horizontal surface involves using the Durham gravimetric pollen collector (Durham 1946). The advantage of the method is its simplicity and cheapness, as well as the ability to get a clear idea of the qualitative composition of aerosols. The vast majority of modern aeropalynological measurements are carried out using volumetric methods. This research method is supported by the IAA and EAN and is used by most researchers. The air along with the pollen is collected by Hirst-type samplers, such as VPPS 2000 (Lanzoni s.r.l., Bologna, Italy) or the Burkard 7-day recorder spore-trap (Burkard Manufacturing Co. Ltd., Hertfordshire, United Kingdom)(Galán Soldevilla et al. 2007). The volumetric method is accepted as the main method for monitoring the presence of pollen in the air, as it is more accurate and better reflects the amount of pollen inhaled by humans (Cornell et al. 1961; Galán Soldevilla et al. 2007; Vorobets and Kalynovych 2010; Boullayali et al. 2024). However, the gravimetric method can be used for a preliminary survey to measure the prevalence of pollen in the air when volumetric pollen samplers are not available.

Recent studies highlight a shift toward automated, sensor-based, and algorithmic pollen monitoring systems that enhance temporal resolution of aerobiological data. Devices integrating optical imaging, fluorescence, and machine-learning algorithms now allow real-time identification and counting of airborne pollen (Buters et al. 2024; Chaves et al. 2024; Lucas and Bunderson 2024). These approaches represent a major advancement beyond traditional gravimetric and volumetric techniques, reducing manual workload while improving analytical reliability.

In this study, pollen from woody plants and its allergenicity were examined in two administrative districts of Kharkiv: Novobavarskyi and Saltivskyi. The aim was to analyze the species diversity of woody plants with allergenic properties and their allergenic load during the growing season using aerial pollen survey. To achieve this, we conducted the following tasks: (1) measurement of the amount of pollen from woody plant species with potential allergenicity, and (2) determination of the periods with the highest pollen allergenic loads in the two administrative districts of Kharkiv using aerial pollen survey.

The structure and species composition of urban tree vegetation largely determine the variability observed in aerobiological pollen data. For instance, in 2010, maximum B. pendula pollen concentrations (grains/m³) recorded with a “Burkard Sporewatch” sampler at a 15-m height reached 1,450 in Vinnytsia, 2,364 in Poltava, 931 in Donetsk, 60 in Dnipro, 317 in Odesa, and 46 in Simferopol (Rodinkova 2013b). In our study, the highest concentration measured with Durham traps at the same height was 135 grains/m³. These values are consistent with aerobiological data from other Ukrainian cities, indicating that the results are reliable and reflect regionally comparable levels of airborne pollen, despite local differences in vegetation composition and microclimatic conditions.

While the Durham sampler measures pollen deposition (grains/cm²) rather than true airborne concentrations, several studies have shown that these values can be converted into approximate volumetric equivalents using Stokes’ law and established correction factors (Durham 1946; Belmonte et al. 2000; Jones et al. 2024). Although such conversions inevitably involve uncertainty related to pollen type, grain size, and meteorological conditions, the resulting values correlate well with patterns obtained from volumetric samplers. For this reason, expressing our results as pollen grains/m³ provides a useful and interpretable measure of airborne pollen exposure in Kharkiv, where volumetric monitoring has not yet been implemented.

Aerial pollen survey in two sites in Kharkiv detected pollen from sixteen species of woody plants, both indigenous and introduced. In general, the assortment of species in each district of Kharkiv may differ slightly. Several factors affect the species diversity and air pollen concentrations of different districts of the city. For example, in Novobavarskyi district, J. regia is planted by residents in private gardens near their houses for food purposes. Because the young trees have not yet entered the reproductive phase, pollen was not detected for these species. Ligustrum vulgare pollen was not detected, likely because the hedges are cut before flowering.

The pollen we recorded was mainly from anemophilous plants. These plants do not have attractive flowers but release large amounts of pollen and are planted in large quantities. Species with ornamental flowers, such as T. cordata, A. hippocastanum, and A. platanoides, release less pollen compared with previously discussed species and are less frequently planted. Our findings, which indicate a more appropriate use of dioecious plants should be considered in landscaping (with pistillate flowers only), are consistent with those of other researchers (Kuchcik et al. 2016; Nowak and Ogren 2021; Magyar et al. 2022).

It is also possible to confirm the relevance of the obtained data by correlating the amount of pollen grains present in the air at the survey sites (Table 3) with pollen production coefficients (Po) according to Magyar et al. (2022) and the scale of pollen grain concentration in the air according to Rodinkova and Bilous (2009). On this scale, low, moderate, high, and very high pollen concentrations correspond to < 15 pollen grains/m³; 15 to 90 pollen grains/m³; 91 to 1,500 pollen grains/m³; and > 1,500 pollen grains/m³, respectively. For species with Pos of 1, concentrations lower than 90 pollen grains/m³ were recorded at the survey sites in Kharkiv, i.e., they released a moderate concentration of pollen according to the Rodinkova and Bilous scale, except for P. nigra var. italica. This is a popular tree species for landscaping in Ukrainian cities; therefore, despite its low pollen productivity, it released high amounts of pollen in our study sites. Also, tree species that released more than 90 pollen grains/m³, i.e., high pollen concentrations according to the Rodinkova and Bilous scale, have coefficients of 2 according to Magyar et al. (2022), except for J. regia, which is rare in the region; thus, only moderate amounts of its pollen were recorded at the survey sites.

In addition to a plant’s potential to produce large amounts of pollen, it is essential to consider how much of that pollen is actually released into the surrounding air. In this study, we focused primarily on pollen collectors positioned at a height of 1.5 m, corresponding to the average human breathing zone. Collectors placed at 15 m contained 1.5 to 3.5 times fewer pollen grains than those at 1.5 m (Table 3). Several factors may explain this difference: some pollen types are relatively large and not fully anemophilous; physical obstacles such as foliage or buildings may have reduced pollen dispersion; and variations in wind direction or velocity could also have influenced deposition. However, because of the high variability and limited sample size, the data obtained at 15 m did not reach statistical significance and should be interpreted with caution. Additional measurements are required to confirm these preliminary findings.

This study represents the first systematic assessment of airborne tree pollen in Kharkiv, a large Eastern European city where the majority of existing trees are approaching or have already reached their age limits. As urban green infrastructure renewal becomes increasingly urgent, the selection of tree species for future plantings must take into account not only climatic adaptation and aesthetic considerations but also the allergenic burden associated with pollen release. Our results provide baseline data on the seasonal dynamics, taxonomic composition, and relative allergenic potential of the most common woody species in Kharkiv.

In the Novobavarskyi and Saltivskyi districts of Kharkiv, aerial pollen survey revealed pollen from 16 species of woody plants, the vast majority of which are anemophiles from the Salicaceae and Sapindaceae families. They are represented by dioecious and monoecious trees (evergreen, deciduous) and shrubs (evergreen, semi-evergreen, deciduous). We found that species with significant allergenic properties included not only introduced species but also indigenous species, such as B. pendula and C. avellana. Corylus avellana, B. pendula, P. sylvestris, and male specimens of J. sabina release significant amount of pollen with very high degrees of allergenicity.

The PL has been proposed to calculate levels of allergenic pollen during a particular period of the growing season. It combines both the quantitative indicator of air saturation with pollen grains and the qualitative characteristic of allergenicity of the studied tree species using their CARE-S indices.

In early and mid-May, pollen from the largest number of tree species was recorded at both sites, with B. pendula and P. sylvestris having the most allergenic pollen. The concentration of pollen grains in the air and the allergenic load index were highest during this period. The period between late May and early June also has a high allergenic load index. This is when the highest depositions of P. sylvestris and J. sabina pollen are found in the air. Thus, the most likely periods for allergies in Kharkiv residents occur during the pollination of allergenic tree species in the first half of May and in early June. However, when species begin flowering depends on temperature conditions, and these are not the same each year.

To understand the full picture, it is necessary to conduct aerial pollen monitoring in Kharkiv, using the volumetric method, which gives more accurate results, as well as to conduct aerial pollen monitoring of herbaceous plant species. This will allow us to identify the areas most likely to affect allergy sufferers, provide recommendations for further planning of landscaping works and reconstruction, and create a pollination calendar.

Thus, although Ukrainian scientists conduct aeropalynological research in the fields of medicine and ecology, the network of aerial pollen monitoring stations in Ukraine should be expanded, but this requires funding, modern equipment, trained professionals, and a legislative framework. Such a framework will make it possible to create a list of plants and consider their specific features to obtain the positive effect of their ecosystem services and create a green network in the city that will be safe for the health of its dwellers.

The authors reported no conflicts of interest.