Siitepolykausi lisaa terveysongelmia

Pollen season increases health problems and even mortality

Pollen forecasts appear in weather forecasts around mid-March when alder and hazel start to bloom. It is common knowledge that people with asthma and allergies get symptoms but the APTA project showed that the start of the pollen season also increases mortality due to respiratory and cardiovascular diseases.


“The APTA project produced new results on the health effects of pollen. We made a completely new observation that a drastic start of the pollen season, i.e. the abundant flowering of alder, increases mortality due to respiratory diseases by as much as 20% and mortality due to cardiovascular diseases by 9%”, says Professor Jouni Jaakkola from the University of Oulu, leader of the project.

The APTA project also included a meta-analysis of 12 studies that suggests that increase of ten pollen grains per cubic metre of air increases lower respiratory tract symptoms and other allergy and asthma symptoms.

“Upper respiratory tract symptoms and eye symptoms can increase even more, but short-term exposure did not affect pulmonary function”, says Professor Jaakkola.

This was the first time that the individual pollen exposure and symptoms of people with allergic rhinitis and/or asthma were studied.

“We measured the pollen exposure of 20 people with asthma and allergic rhinitis for four weeks with personal pollen samplers. The participants also kept a symptom and medication diary.”

Peak pollen concentrations increased typical allergy symptoms, such as watering of the eyes, runny nose and itching, on the very same day. Skin and lower respiratory tract symptoms, such as wheezing, appeared in two to three days.

After the pollen peak, the symptoms remained at a higher level even though the exposure lowered, for example, due to rain. A new pollen peak exacerbated the symptoms again.

APTA (the Influence of Air Pollution, Pollen and Ambient Temperature on Asthma and Allergies in Changing Climate) is a research project funded by the Academy of Finland. The participants include researchers from the field of environmental health and geography from the University of Oulu and Professor Jaakko Kukkonen’s team from the Department of Meteorology.

Less grass pollen in urban areas

In the APTA project, geographers and researchers in environmental health measured pollen concentrations at the breathing height and compared the results with land use.

“We had 16 observation stations in the Helsinki metropolitan area where we collected data on the concentrations of birch and grass pollen at the height of 1.5 metres”, says Adjunct Professor Timo Hugg from the Center for Environmental and Respiratory Health Research (CERH).

Collaboration with geographers provides researchers in environmental health with access to land use materials and geographic information methods that can be used to model and forecast pollen concentrations both locally and regionally.

A team led by Jan Hjort, Professor of Physical Geography, University of Oulu, modelled measured pollen concentrations from urban gradient in relation to land use and other environmental variables.

“Land use had a clear effect on the amount of grass pollen in inspired air: the more urban the setting, the less grass pollen in the air”, comment Hugg and Hjort on the results of the cooperation.

On the average, there were large differences in the amount of grass pollen between the Helsinki city centre and Espoo. During the flowering period, there are only a few pollen grains per cubic metre of air in the city centre but dozens in the outskirts of Espoo.

“The threshold for evoking allergic symptoms is a few dozen pollen grains per cubic metre of air.  Theoretically, city centres could provide an escape for people with hay fever”, says Timo Hugg.

The concentrations also varied distinctly depending on the time of the day: there was considerably less pollen in the air in the morning than in the afternoon. As the temperature increased, the amount of pollen increased.

There is no escape from birch pollen, however, not even in an urban area.

”During the peak flowering season, the concentration of birch pollen can exceed 1,000 grains per cubic metre of air, even in city centres. In the spring, there are also inorganic particles and compounds, such as road dust and air pollution, in the air in addition to pollen, and this cocktail can be dangerous to people with asthma or allergies”, says Timo Hugg.


Pollen forecasts are prepared in Turku

Birch pollen is one of the most important pollens that cause allergy, and this spring can prove particularly difficult for people with allergies – abundant flowering of birch is predicted because conditions last summer were particularly favourable for the development of flower buds.

But how is the pollen concentration studied and how are forecasts prepared based on this data? Annika Saarto is the head of the Aerobiology Unit of the University of Turku, responsible for pollen forecasts. The Unit also participates in the APTA project.

“We have nine observation stations around Finland were pollen data is collected with a Burkard spore trap. The device’s adhesive tape moves at 2 mm per hour, and the collected pollen is analysed within a two-hour window”, says Saarto.

The Burkard pollen traps are placed approximately 15 metres above the ground. One trap is located on the roof of a building in the Linnanmaa campus of the University of Oulu.

During the pollen season, the adhesive tape is replaced twice a week and sent to Turku for analysis. The tapes are processed in a laboratory, the pollen is counted using a microscope and the number of pollen grains per cubic metre of air is calculated based on the result.

“Our pollen forecasts are based on the Finnish Meteorological Institute's weather forecasts and pollen distribution models”, explains Saarto.

Long-range transport must be taken into account because the wind carries pollen all the way from Central and Southern Europe. If the wind is from the south when birch trees are flowering in Southern Finland, people can have allergy symptoms in Lapland even though flowering has not started yet in the north.

Text: Satu Räsänen

Main photo: Mikko Törmänen

Last updated: 29.5.2019