According to the 2013 issue of the German Federal Health Gazette, around 15 to 20 percent of the population in Germany suffers from hay fever. Because Europeans and North Americans spend over 90 percent of their time in closed rooms, pollen concentrations in buildings need to be taken into account. In addition to meteorological factors, the type and frequency of room ventilation was also taken into account in the study published in the specialist journal “Indoor Air”.
During their investigations, the authors concentrated on birch pollen, as it triggers allergic reactions with particular frequency, as does grass pollen. Birches are ‘colonizers’ (pioneer plants), which means that they begin with their reproduction phase early. As wind-pollinated plants, they produce particularly large amounts of pollen, which results in their high potential for causing allergies.
For the study, birch pollen concentrations were measured in five different rooms and in front of the adjacent windows in April 2015. Among other things, the rooms differed in how they were aired or ventilated.
The mobile pollen traps were placed at a height of 1.2 meters, which corresponds to the average height at which a person breathes when working at their desk. They were located at a distance of 2.5 meters from the corresponding room window. A second pollen trap was attached to each of the window sills.
Furthermore, a standard Burkard pollen trap was installed on the building roof at a height of 15 meters next to the meteorological station to measure the baseline concentration. This measurement of pollen in the surrounding air was taken daily from March to November according to the standards of the European Aeroallergen Network (EAN).
From April 13 to 29, the blooming of 56 birches in the near surroundings was observed. Ten of the trees were located in the direct vicinity of the offices examined, and the remaining 46 were located at a distance of 0.5 to 15 kilometers. The data on the general weather situation, on the other hand, came from a station of Germany’s National Meteorological Service (DWD) in Freising. Directly in front of the rooms, the temperature, humidity, and wind speed and direction were also measured.
Huge differences between individual rooms
As was expected, the pollen concentrations in the rooms were generally lower than outside. The pollen concentration ratios measured ranged from seven to 75 percent. This is because the airing/ventilation strategy plays a big role: For example, for the purposes of the study, one of the rooms was aired for five minutes every two hours. This room exhibited the lowest pollen concentration compared to a neighboring room in which the window was left tipped open all the time.
The concentration was also higher in a room with an open window and in a chemical laboratory with automatic air extraction. Periodic, intensive airing can reduce pollen concentrations by up to two thirds as compared to the maximum pollen concentrations achieved in a room in the study. Hence, for a particularly effective way of keeping birch pollen out, the authors advise those suffering from pollen allergies to only air the rooms they are located in periodically and intensively.
One other influencing factor is the amount of foot traffic in an office. Over time, the pollen concentration in a room increases. This may suggest a correlation with the number of colleagues entering and leaving a room, as pollen attaches itself to clothing. Furthermore, pollen also accumulates in household dust if cleaning is not done at all or only infrequently. This even takes place outside the pollen season. Hence, for allergy sufferers, regular dusting is an important measure to minimize allergic reactions.
A. Menzel, M. Matiu, Michaelis, S. Jochner: Indoor birch pollen concentrations differ with ventilation scheme, room location, and meteorological factors, Indoor Air 2016. DOI: 10.1111/ina.12351
Technical University of Munich
Professorship of Ecoclimatology
Prof. Dr. Annette Menzel