Allergenic airborne grass pollen in Szczecin, Poland.

Grass pollens are known as very potent aeroallergens. The aim of the study was to analyse the grass pollen season in Szczecin (western Poland) in the years 2000-2003 and to establish a relationship between the meteorological conditions and the pollen counts of Poaceae. The meteorological parameters analysed were the maximum and mean air temperature, relative humidity, amount of precipitation and wind speed. Measurements were performed mainly by the volumetric method. In parallel, gravimetric monitoring was conducted in 4 Szczecin city districts in order to establish the spatial distribution of pollen in aeroplankton. Pollen seasons were defined as the periods in which 95 % of the total catch occurred. In the 4 years studied, the lowest concentration of grass pollen was observed in 2000 with the maximum value of 123 pollen grains in 1 m3 per 24 h. In subsequent seasons, the concentration of Poaceae pollen increased and the highest concentration of grass pollen, equal to 809 pollen grains in 1 m3 per 24 h was noted in 2003. The majority of Poaceae species have constant periods of pollen release and the high number of their species means that the pollen season is long and lasts from the beginning of May until the middle of September. The longest pollen season was observed in the year 2000 when the lowest pollen count was found. In sensitive persons the symptoms of pollinosis occur after some threshold pollen count value, which for grass is 30 grains in 1 m3 per 24 h. Therefore, the greatest threat from Poaceae pollen allergens is noted from the middle of May and until the end of July, and at the beginning of September. Analysis of the pollen distribution in different Szczecin city districts determined by the gravimetric method, has shown that the highest exposure to grass pollen allergens occurs in the districts Zelechowa and Sródmieście, in the area with parks, villas and gardens or garden allotments. However, in the pollen season the threshold Poaceae pollen count value is usually exceeded in the entire city. Statistically significant correlations have been found between the grass pollen count in the air and the maximum wind speed, air temperature, amount of precipitation and relative air humidity. The pollen count of grass is determined by the diversity of local flora and weather conditions, especially by the air temperature and relative humidity.