Significance of sampling height of airborne particles for aerobiological information.

Pollen and spore counts from Burkard traps for routine pollen and spore sampling placed at 15 m above ground and at ground level were compared. Daily counts of most pollen types were higher on the ground than at roof level, but the counts were significantly correlated. The ratios of pollen frequencies at high and low levels varied between 1.0 and 11.5. The most prominent differences were recorded for herbaceous pollen (e.g. Artemisia counts 11.5 and Poaccae counts 4.4 times higher at ground level) and in Botrytis and Ustilaginales spores. Tree pollen grains and basidiomycetous spores were more equally distributed. Wind speed did not affect the variation of pollen frequencies at either height. Large spores are not so unevenly distributed as previously supposed. Artemisia and grass pollen was detected 1 to 2 weeks earlier at ground level than on the roof. It is therefore concluded that especially the beginning of flowering should be monitored at a low level.

Pollen seasons: forecasts of the most important allergenic plants in Finland.

Occurrence of airborne pollen in Finland has been studied for 10 years in Turku (southern Finland), 8 years in Oulu, 4 years in Kuopio (central Finland) and 7 years at Kevo (northern Lapland). Observations on the pollen seasons of alder, birch, grasses and mugwort are presented. All these pollens occur in south and mid- Finland in quantities capable of causing allergy symptoms. Except for birch pollen, allergenic pollens occur in far lower concentrations than in central Europe. In northern Lapland only birch and pine pollen concentrations are high. Pollens may occur without signs of local flowering when there are southerly winds. This finding suggests that long-distance transport is an essential contributing factor to the occurrence of pollens. There are wide year-to-year variations in the start of pollen seasons and the quantities of pollens. The variations in the start of birch and grass pollen seasons could very much depend on the mean temperature in April. However, a forecasting model based on this and other spring-time temperature parameters often fails to give sufficiently accurate forecasts.

Forecasting the presence of atmospheric pollens.

The forecasting process includes several aspects. The scientific aspects include (i) a priori observations, like statistics of weather attributes during recent years, variation of earlier atmospheric pollen amounts, and general correlations between weather factors and pollen frequencies. (ii) The present-day observations are made closer to the flowering season, and they include e.g. the development of the present and forecasted weather, the development of the flower buds, and information obtained from other countries. The practical aspects include effective television, radio and newspaper service, necessary education and information, rapid data analysis and transfer systems, and good national and international cooperation.

Localization of allergenic molecules in pollen grains.

The wall of the mature pollen grain contains several layers, of which the outermost, the exine, is formed by the mother plant. Numerous proteins are incorporated in the exine. During the normal germination process on the stigma, these proteins interact with the stigmatic proteins. The interaction results into either enhancement or cessation of the pollen tube growth. It has been shown that most of these proteins diffuse into surrounding solutions already in a few seconds. They also cause allergic reactions in man. The diffusion of proteins and their allergic properties are not dependent on the germination of the pollen grains, and probably not either on their viability. The pollen grains of conifers are very weak allergens; their structure and function are different from those of the remaining flowering plants.