The Identification of Morphology, Structure and Study of Seasonal Variation of Airborne Fraxinus Excelsior Pollen Grains in the Tehran

Background: European ash (Fraxinus excelsior) is a common cause of asthma, allergic rhinitis and allergic conjunctivitis. Therefore, it is essential to study the period and duration of the flowering in airborne in each region/area. In this research, was to evaluate the relation between ash pollen counts with meteorological and air pollution factors in Tehran for six years. Methods: At the First, the districts of Tehran were classified as northern, southern, eastern, western and central regions and the near of Tehran is the control zone. Pollen samples were collected from F. excelsior trees planted in the areas of Tehran and also in non-polluted area Situated outside the city. Scanning electron microscopy was used to examine and compare shapes and structures of non-polluted and polluted pollens.  An attempt was made to pollen counts determined by the two methods (volumetric7-day spore trap and gravimetric durham method) during six years (the Jan2010 to jun2015). Airborne ash Pollens were collected on a slide for 24 hour period and the slides were stained and examined under microscope. The relationship between the ash pollen counts, and the meteorological parameters including the mean values of high/ low rates of temperature, sunshine hours, high/ low relative humidity, wind speed and raining was investigated. Also air pollution data, such as Co, NO2, SO2, O3, and PM10 and PM2.5 were all obtained from the five study areas in Tehran for finding their relation by grass pollens count. Results: Our microscopic examinations showed that air pollution considerably improved the fragility of pollen exine, causing numerous cracks in its surface and facilitating pollen content liberation. A pollen calendar of ash pollen types was identified in the six years study period areas of Tehran.  Pollen production was higher in the south and center area and was lower in the other areas of Tehran. Major pollen seasons were recognized Jan to April. Highest pollen counts were obtained in March and lowest in the Jan.  The ash pollen calendar and its association with meteorological and air pollution factors related mainly to daily temperature, sunshine hours, wind speed and Co, NO2 and PM2.5. Conclusions:  The ash pollens seasonal variation that is specific for each area in each country can help allergic patients for decision in their life in every day and for physicians to attend allergic disease management. So we hope these data be use full for patients and physicians in Tehran (capital of Iran). Finally, the results showed pollutant can be a cause of extending the period of pollination.