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8/05/2009 - Press release

Air pollution also causes asthma in adults

The greater the amount of pollution due to suspended particulate matter from traffic in residential areas, the greater the risk of developing asthma. This not only affects children, but also non-smoking adults. This was the conclusion reached by the SAPALDIA cohort study backed by the Schweizerischen Nationalfonds (Swiss National Foundation on Scientific Research) in collaboration with the Centre for Research in Environmental Epidemiology (CREAL).

Asthma is an inflammatory disease of the respiratory tract. It is accompanied by permanent hypersensitivity to a large amount of stimuli and causes attacks of respiratory failure. Asthma is the most common chronic disease in children; however adults can also develop this disease. Suspended particulate matter emitted by traffic is especially dangerous to human health, as it is linked to the emergence of asthma in non-smokers.

The study was conducted in Switzerland, from 1991 to 2002, within the framework of the SAPALDIA study from which a total of 2,725 non-smokers between the ages of 16 and 60 were selected. During this time, 41 people from a total of 2,725 (1.5% of all studied) developed the disease as non-smokers. This is the news presented by the SAPALDIA cohort study, which was published in the journal Thorax (*).

Arguments for a debate on town planning

The 41 cases of asthma were not randomly distributed throughout Switzerland, but rather mostly emerged in built-up areas with heavy traffic. In areas where traffic was not as heavy, the risk of developing asthma was reduced. Dr. Nino Künzli, researcher from the Centre of Research in Environmental Epidemiology (CREAL) and the Municipal Institute for Medical Research (IMIM), as well as the main contributor to the study who recently became a professor at the Institute for Social and Preventive Medicine at the University of Basel, states: “Our results contribute to the debate on town planning regarding the type of buildings that should be built and how far they should be from heavy traffic.” According to Künzli, the only regulation of this kind in existence – in California new schools cannot be built less than 300 metres away from motorways – tallies with the conclusions of the study.

Global model Researchers calculated the exposure of those studied with a global model, combining the emissions of suspended particulate matter from traffic during the entire period with meteorological data such as wind and rainfall information. In this way, researchers could establish the exposure time to suspended particulate matter for the eight regions from which the subjects came.

From 1991 to 2002, in Switzerland, average air pollution due to suspended particulate matter from traffic dropped from 2.84 to 2.25 micrograms per m3. In reference to this, the reduction in pollution in urban areas such as Basel and Geneva was greater than in rural areas such as Davos or Montana, where in 1991 the air was already clean. Although the reduction of pollutant emission is good news, new cases of asthma continue to emerge. “This is reason enough to only sell cars with minimal or no pollutant emissions,” states Künzli.

Researchers restricted their study to people who had never smoked. Tobacco smoke essentially contains the same pollutant substances as those produced by traffic, but in higher concentrations. For this reason, although they may not be exposed to air pollution, the risk of developing asthma is greater for smokers.

(*) Nino Künzli, Pierre-Olivier Bridevaux, L.-J. Sally Liu, Raquel Garcia-Esteban, Christian Schindler, Margaret W. Gerbase, Jordi Sunyer, Dirk Keidel, Thierry Rochat, from the SAPALDIA team (2009): Traffic-Related Air Pollution Correlates with Adult-Onset Asthma among Never-Smokers. Thorax Published Online First: 8 April 2009. DOI: 10.1136/thx.2008.110031

SAPALDIA (Swiss Cohort Study on Air Pollution and Lung Diseases in Adults) The objective of the SAPALDIA study is to discover the causes that trigger changes in respiratory and allergic symptoms over time. In 1991 the cohort study measured the pulmonary function and possible allergies of 9,651 participants, who were chosen randomly from eight different areas. In 2002, 8,047 people provided new information on the condition of their health. Another health examination should take place in 2010.

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