Birch pollen grains are one of the most important groups of atmospheric biological particles that induce allergic processes. The fluctuation pattern of birch pollen seasons in selected cities of Poland is presented. Measurements were performed by the volumetric method (Burkard and Lanzoni 2000 pollen samplers). The distributions of the data were not normal (Shapiro–Wilk test) and statistical error risk was estimated at a significance level of <em>α</em> = 0.05. Pollen season was defined as the period in which 95% of the annual total catch occurred. The linear trend for the selected features of the pollen season, skewness, kurtosis and coefficient of variation (<em>V</em>%) were also analyzed. During the 12–14 years of study, the beginnings of birch pollen seasons were observed 7–14 days earlier, the ends were noted 5–10 days earlier, and the days with maximum values occurred 7–14 days earlier compared to the long-term data. The left-skewed distribution of the pollen season starts in most sampling sites confirms the short-lasting occurrence of pollen in the air. The threat of birch pollen allergens was high during the pollen seasons. If vegetation is highly diverse, flowering and pollen release are extended in time, spread over different weeks and occur at different times of the day. Flowering time and pollen release are affected by insolation, convection currents, wind, and turbulence. Therefore, pollen seasons are characterized by great inter-annual variability.

Exposure to airborne pollen allergens results in allergic symptoms in subjects who are sensitized. The paper presents diurnal variation in the counts of airborne allergenic pollen of selected trees (Betula L., Alnus Mill., Corylus L., Fagus L. and Ulmus L.) in two localities differing in the degree of urbanization: the city of Szczecin (urban) and the village of Gudowo, West Pomerania in northwest Poland (rural) in the years 2012–2014. The measurements were made by the volumetric method using a Burkardtype sampler operating in a continuous mode. The greatest similarities in the beginning of the main pollen season between the two sites studied were observed for birch and elm trees, while in the length of the main pollen season, for birch and alder trees. Pollen counts of alder and hazel reached higher levels in the rural area, while the levels of ash tree pollen counts were higher in the urban area. The level of birch tree pollen counts was similar in the two sites studied. For the majority of taxons observed in the urban and rural areas the dynamics of hourly changes in tree pollen counts were similar. The pollination peak was noted in the daytime, usually in the afternoon. For ash and elm trees increased pollen counts were observed at nighttime, while the birch tree pollen counts were at a high level for most of the 24 h cycle. The knowledge of seasonal and diurnal variations in tree pollen counts is crucial for prevention in patients with allergic rhinitis, sensitized to tree pollen allergens.

The aim of the study was to investigate the concentration of <em>Alnus</em> L., <em>Corylus</em> L. and <em>Betula</em> L. pollen in the village of Gudowo (Western Pomerania, Poland) in the years 2012–2014 in order to estimate the threat of allergenic tree pollen in this rural region. Measurements were performed using the volumetric method (VPPS Lanzoni 2000 pollen sampler). The duration of the pollen season was determined by the 98% method, taking days on which, respectively, 1% and 99% of the annual total pollen grains appeared as the beginning and end of the season. Pollen grains from hazel occurred in the air as the first ones, before pollen grains from alder and birch. The earliest beginning of the hazel pollen season was recorded in 2012, whereas alder and birch pollen seasons started the earliest in 2014. Daily maximum pollen concentrations of the investigated taxa were recorded in 2014. Birch pollen allergens posed the largest threat to pollinosis sufferers. In the years 2012–2014, pollen concentrations equal or higher than threshold values, at which people with pollinosis show allergic symptoms, were recorded most frequently for birch, hazel, and alder (25, 19, and 14 days, respectively). The highest hourly alder pollen concentration was recorded at 16:00 and in the case of hazel at 15:00. The diurnal distribution of birch pollen concentrations does not show any distinct peaks.

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A b s t r a c tThis paper presents the course of the pollen season of selected allergenic taxa (Secale spp., Rumex spp., Plantago spp., Urtica spp., Artemisia spp., Chenopodiaceae and Poaceae) in Szczecin (2009) and Gudowo (Western Pomerania, Poland) (2009)(2010), and also the flowering pattern of Chenopodium album, Artemisia vulgaris and Secale spp. Pollen deposition was studied by the gravimetric method using a Durham sampler. In 2010 the flowering period of the studied taxa was shorter than in 2009 and its onset was observed later; the maximum values of daily pollen deposition were lower. Pollen grains of most of the taxa studied appeared in the atmosphere of the city earlier than in the rural area, but in the rural area significantly higher values of daily deposition were recorded. The effect of weather conditions on pollen fall in Szczecin in 2009 was analysed. Statistically significant positive correlations with pollen deposition were found only with maximum, minimum, and mean air temperature, dew point and maximum wind speed, while a negative correlation was found with precipitation and -only for Rumex pollen grains -with air humidity and pressure.