Analysis of Corylus pollen season in Poland in 2020

In Poland hazel is one of the earliest flowering plants and in phenology it belongs to indicator plants that mark the beginning of early spring. Hazel pollen grains contain allergens that are a cause of pollen allergy during the early spring period. The aim of the present study was to compare Corylus pollen seasons in 2020 in the following 11 cities located in different regions of Poland: Szczecin, Bydgoszcz, Zielona Gora, Wroclaw, Opole, Sosnowiec, Piotrkow Trybunalski, Warsaw, Lublin, Olsztyn, and Bialystok. This research was conducted using the volumetric method and Burkard or Lanzoni pollen samplers. Pollen season duration was determined by the 95% method. This study analyzed the specific parameters of the pollen season (start, end, peak value, peak date, annual total) and also determined the number of days with a concentration exceeding the threshold values at which the first allergy symptoms in people sensitized to hazel pollen and symptoms in all allergic patients occur, respectively. The hazel pollen season in 2020 began relatively early, between January 11^th and February 2^nd. The season start was recorded earliest in Opole and latest in Olsztyn and Bialystok. The study found that the pollen season started earlier in the western part of Poland than in the eastern regions. The highest maximum Corylus pollen concentration was recorded in Lublin (388 P/m³), whereas the lowest one in Bydgoszcz (48 P/m³). The maximum daily concentration of Corylus pollen grains was recorded in different periods in the individual cities, while the peak concentration values occurred between January 31^th and March 4^th. The highest risk of allergy in people sensitive to the pollen of this taxon was found in Lublin since the most days with a pollen concentration exceeding the threshold value were observed in this city. Lublin was found to have the highest annual total values and they were 1.6–5.6 times higher than in the other cities. The highest annual pollen sums and peak values as well as the highest number of days with a concentration exceeding the threshold value had also been recorded in Lublin previously.