In an experimental field study, airborne particulate birch and grass pollen allergens were sampled with a cascade impactor on the roof of an office building in the centre of a middle-sized town in Sweden. The impactor separated particles into eight size fractions. Simultaneously, inhalable pollen allergens in the indoor air were sampled in offices of the building. Significant amounts of the outdoor pollen allergens were found on particles much smaller than the pollen grains. These small particles could penetrate the fine filters (quality F6) of the building’s ventilation system. By taking into account the effectiveness of the installed ventilation filters, the pollen allergen concentration indoors could be well predicted, thus pointing out the supply air as the main source of indoor pollen allergens. Comparison of data from workdays with those from weekends indicated that secondary emissions of pollen allergens brought indoors by people (on clothes, hair, shoes etc.) were insignificant.

In an experimental study, ventilation filters of high quality (F7 & F9) were tested regarding their efficiency in collecting birch pollen allergens in outdoor air. The birch pollen grain concentration in outdoor air was measured at the same time as pollen allergen and particle number concentrations were measured before and after the tested ventilation filters, thus enabling collection efficiency calculations. Simultaneously, the size distribution of birch pollen allergens was measured in outdoor air using a cascade impactor. The study confirms previous indications that pollen allergens may occur in outdoor air in particles much smaller than pollen grains, and can penetrate ventilation filters to a larger extent than might be expected. This entails that although the high quality filters collect most of outdoor air pollen allergens, a significant exposure dose to these allergens can occur in the indoor environment, especially when considering the fact most people stay much more indoors than outdoors. The study also confirms previous similar indications attained with grass pollen allergens, in that the allergenic particles tend to penetrate ventilation filters to a greater extent than other airborne particles.

In an experimental study, commonly used ventilation fine filters were tested regarding their efficiency in collecting airborne particles and grass pollen allergens from outdoor air. Grass pollen allergen and particle number concentrations were measured before and after the filters, enabling collection efficiency calculations. Simultaneously, the size distribution of grass pollen allergens was measured in outdoor air using a cascade impactor. The study confirms previous indications that pollen allergens occur in the outdoor air as particles much smaller than pollen grains, and can penetrate ventilation filters to a larger extent than might be expected. The initially high collection efficiency of synthetic, electrostatically charged filters declined significantly with time of use (dust load), whereas glass fiber filters showed steady performance. A slight tendency for pollen allergenic matter to penetrate ventilation filters more than other airborne particles was noted, but no difference in the response to electrostatic charge of filters could be seen.

Catalytic combustion of methane was carried out using platinum catalysts supported on low-and high-surface area alumina (denoted respectively as LSA and HSA) and platinum supported on silica. Methane conversion was the highest for platinum supported on LSA alumina, smaller for Pt/HSA alumina and the smallest for Pt/silica. However, the 3 wt.% Pt/HSA catalyst was found to show the highest selectivity.

The number of people sensitized to the major birch pollen allergen Bet v 1 in industrialized countries is vast and still rising. The purpose of this study was to develop a method with sensitivity high enough to measure the Bet v 1 content of a few birch pollen grains without the interference of environmental factors such as diesel particles, ozone level, humidity, temperature and precipitation. Grains were collected from catkins at two locations in Sweden over a period of 5 years. Allergens were extracted over polytetrafluoroethylene (PTFE) filters and Bet v 1 quantification was made with a luminescence immunoassay. The average content of Bet v 1 was 3.6 ± 0.6 pg per pollen grain for samples collected in three different pollination seasons. This is the first in a series of controlled experiments on the release of the major allergen Bet v 1 from birch pollen grains.