Led by the Barcelona Institute of Global Health (ISGlobal), Spain, the new study set out to investigate whether exposure to air pollution could reduce the positive effect of physical activity on lung function, both in current smokers and in those who have never smoked.

Although a previous study conducted by some of the same researchers already found that regular physical activity was associated with better lung function among smokers, the research did not analyse exposure to air pollution.

For the new study, the researchers analysed data from 2,801 non-smokers and 1,719 smokers from nine European countries — Belgium, France, Germany, Italy, Norway, Spain, Sweden, Switzerland and the United Kingdom.

Participants were aged between 27 and 57 at the beginning of the study and followed for a period of ten years.

During this time participants were asked to complete spirometry tests to assess lung function. They were classified as being active if they exercised twice or more times a week and for at least one hour.

Exposure to air pollution was estimated as the annual average concentration of nitrogen dioxide (NO2), a pollutant generated by traffic, and particulate matter PM10, which are particles of pollution less than 10 microns across, and the smaller fine particulate matter, PM2.5, which are particles smaller than 2.5 microns in diameter that can penetrate deeply into the respiratory tract.

The findings, published in the journal Environment International, showed that regular physical activity was associated with higher levels of lung function among current smokers, regardless of the level of air pollution in their city.

For participants who had never smoked, physical activity did appear to have benefits for lung function for those living in areas with low or medium levels of air pollution, although the results were less clear for those who lived in urban areas with higher levels of pollution.

“The results reinforce the message that physical activity is beneficial for health, including respiratory health,” commented Elaine Fuertes, first author of the publication. “However, our data suggest that the benefits of physical activity may be reduced among non-smokers living in cities with high air pollution levels. If confirmed, this means that policies aimed at controlling air quality levels would maximise the benefit of physical activity promotion policies.”

European research published earlier this year also found that exercise can still help reduce the risk of a heart attack even when carried out in areas with moderate to high levels of traffic pollution.