Po PolskuAllergen Research Center, Warsaw, Poland
Published in: R. Spiewak (Editor): "Pollens and Pollinosis: Current Problems". Institute of Agricultural Medicine, Lublin (Poland) 1995, pages 18-20.
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Plant pollen grains represent some of the most clinically important allergen sources. It is estimated that 5 to 15 per cent of population suffer from seasonal allergic rhinitis and conjunctivitis (in the age group 19-25 it can be as high as 20 per cent). Pollen grains are male gametes produced by flowering plants. The major allergenic pollen grains come from wind-pollinated plants. Wind-born pollen grains from individual species vary in size, ranging from 17 to 60 µm. For a particle to be clinically significant as an aeroallergen it must be present in significant numbers, be widespread and allergenic.
The major allergens are proteins found in the outer wall and cytoplasm of the pollen grains. Allergenic reactions ensue in susceptible individuals when the pollen grains fall on the respiratory epithelia and their content is released. A characteristic feature of pollen sensitivity is its seasonal pattern of occurrence at the time when pollen is most frequent in the atmosphere. The allergenic content of the atmosphere also varies according to climate, geography and vegetation. The number of pollen grains required to provoke disease is not very clear but studies indicate that the number varies with prior exposure. Thus, the amount of pollen required to initiate symptoms at the beginning of the hay fever season is greater that at the end of the season, an effect known as "priming effect". Studies suggest that between 10 and 50 grains per 1 m3 of the air represent threshold exposure concentration. Taudorf and Moseholm report that in less sensitive individuals 4-10 times higher exposure may be necessary to provoke equivalent symptoms (Taudorf and Moseholn, 1988). In our studies (Rapiejko et al, 1995) the level of 53 pollen grains per 1 m3 was determined as threshold exposure concentration in allergic individuals staying in Warsaw at the beginning of the pollen season (air pollution is an important factor) and 71 grains per 1 m3 in individuals spending that time at Masuran Lakes.
Knowledge of the current atmospheric pollen concentration and pollen forecast is of great interest for clinicians and allergic patients. It allows to achieve better management (prevention, symptomatic treatment and immunotherapy) of hay fever symptoms. A quantitative and qualitative variation in pollen count in each year creates the necessity of constant airborne pollen study. It is also essential to give clinicians and patients an access to the data.
The registration of pollen and spore content of the air has been performed in the USA since 1916 and in the United Kingdom since 1942. In Poland, M. Obtulowicz started palynological study for medical purposes in 1939. In the following years the studies were carried out: 1962 in Krakow and Rabka - A. Weiss, 1969 in Warsaw - M. Dabrowski, 1973-1974 in Warsaw - E. Zawisza, 1976 in Bydgoszcz - R. Gniazdowski, 1978-1979 in Lodz - K. Buczylko and M. Wnuk, since 1982 in Krakow - K. Szczepanek, since 1985 in Krakow - K. Obtulowicz with Burkard volumetric spore trap, since 1987 in Rabka - R. Kurzawa, P. Gawel with Burkard volumetric spore trap, 1988-1990 in Lodz - P. Rapiejko and K. Buczylko, 1989 in Zakopane, Ruciane Nida, and on the top of Kasprowy Wierch (Tatra Mountains) - P. Rapiejko, since 1989 in Warsaw - P. Rapiejko with volumetric spore trap, 1990-1991 in Warsaw - K. Binka, since 1992 in Lodz - K. Buczylko with a volumetric spore trap, since 1992 in Gdansk - M. Latalowa with Burkard volumetric spore trap. Detailed pollen calendars prepared by E. Zawisza for Warsaw (1973-1974) and by K. Szczepanek and K. Obtulowicz for Krakow contributed largely to Polish allergology. In 1989 the first pollen report, worked out by the Allergy Research Center, appeared in print in the "Express Ilustrowany" daily newspaper, Lodz. It gave the start to pollen monitoring network working troughout the country, from which the current data are sent to the Allergen Research Center main office in Warsaw.
At present (Sempember 1995) the Center carries on pollen measurement in 17 continuous operation stations and 5 seasonal ones. It cooperates with the network of 5 measuring stations led by professor K. Szczepanek from Jagiellonian University, Kraków and with self-dependent stations: in Kraków professor K. Obtulowicz - Collegium Medicum of Jagiellonian University, in Lodz professor K. Buczylko - Allergy Center, in Rabka professor R. Kurzawa and P. Gawel, in Gdansk professor M. Latalowa - Gdansk University, in Poznan A. Stach and T. Hoffman - Allergy Center. Data from Poland are sent to European Data Bank in Vienna. Pollen information (current data reports and forecasts) elaborated by Allergen Research Center is available to the public through radio broadcast, television and newspapers. More detailed data have been provided to physicians in the form of Pollen Monitor Bulletin since January 1995.
The basis of any method of pollen sampling is to provide a sticky surface upon which the grains can adhere and through which they may be microscopically examined.
Three groups of sampling devices can be distinguished:
a) gravity samplers,
b) rotating-arm impactors and
c) suction samplers.
The simplest method to collect airborne pollen grains is to let them settle on a sticky surface, where they can be analysed microscopically later. This method is quite commonly used because of its simplicity and low costs. It offers advantages when qualitative data or, at most seasonal prevalence trends are studied and is sufficient especially for comparatively large and abundant particles. Microscope slides or plastic tapes serve as sticky surface. Slides are coated with vaseline, glycerin jelly or other special solution and are exposed during short periods of time.
In 1946 Durham described a standard sampling device. The device is simple to use or construct, is portable and lacks power requirements. Durham sampler provides support for a 1 x 3 inch microslide which is mounted 1 inch above a 9-inch diameter disc. A second 9-inch disc serves as a rain shield and the two are attached by three 4-inch struts. The device is usually placed 150-180 cm above the ground level or at the roof level. Pollen count is expressed here as a number of grains per 1 cm2. Unfortunately, in the natural environment the catch is affected by wind speed, turbulence and the orientation of a slide in respect to wind direction. It has ben shown that the turbulence deflects smaller particles and favours larger ones - 15 µm and above. However, with increased wind velocity there is increased efficiency in the capture of smaller particles. Sometimes the usage of bigger sticky surface is advised. Open dishes such as Petri dishes, beakers, cuvets serve this purpose very well. They offer advantages at times of rainfalls. The autor carried out pollen measurement with Petri dishes placed at roof level of meteorological station at Kasprowy Wierch, Tatra Mountains. Frequent snowfalls did not disturb the study.
Suction samplers extract pollen grains from measured volumes of aspirated air. These devices offer special advantages for the collection of relatively small particles, as those are more responsive to drag forces. Burkard sampler is the most commonly used in Europe and recommended volumetric spore trap. In the device particles are trapped on a sticky tape on a clock-driven drum behind the entrance orifice. The drum moves 2 mm per hour, thus the concentration of airborne particles can be calculated hourly. Pollen count is expressed here as a number of grains per 1 cubic meter. In 1991 in Poland VST-1 Alergo-RP volumetric spore trap was constructed (P. Rapiejko, L. Domanski). Small size, weight and possibility of working in the field (storage battery) are the advantages of this device. It is very useful in seasonal measurement such as holiday season at health resorts.
Each of devices mentioned above has its advantages and disadvantages. The choice depends on the purpose of the study. The purpose has also influence on the selection of the sampling point, which is very important thing. In fact there is no strict standard for the height or position of the sampler. Most sampling sites are situated at 10-30 meters above the ground level. This is supposed to be high enough not to be affected by local disturbance factors. Studies have shown that the first pollen grains are observed at ground level 1-2 weeks earlier than at roof level. So sampling at lower level is helpful in predicting a pollen season. It is advised to set one sampling device at higher, the other at lower level.
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