A new large-scale study has found that exposure to outdoor air pollution appears to be linked with decreased lung function and an increased risk of developing the long-term condition chronic obstructive pulmonary disease (COPD).
Carried out by Canadian, Swiss and UK researchers, the new study looked at data gathered from 3 03, 887 individuals aged 40 to 69 years old taking part in UK Biobank, a large long-term study which includes genomic data on more than half a million UK residents.
As part of the study, participants answered health questionnaires and had their lung function measured using spirometry tests, which assess lung function by measuring how much air can be breathed out in one forced breath.
The researchers also used an air pollution model to estimate participants' exposure in their homes to levels of three types of pollution: particulate matter (PM10); fine particulate matter (PM2.5), which are particles smaller than 2.5 microns in diameter that can penetrate deeply into the respiratory tract; and nitrogen dioxide (NO2).
All are produced by burning fossil fuels from car and other vehicle exhausts, power plants and industrial emissions.
The findings, published in the European Respiratory Journal, showed that for every annual average increase of five micrograms per cubic meter of PM2.5 in the air that participants were exposed to at home, participants showed a reduction in lung function similar to the effects of two years of aging.
For participants living in areas with PM2.5 concentrations above World Health Organization (WHO) annual average guidelines of ten micrograms per cubic meter (10 μg/m3), the rate of COPD was four times higher than among people who were exposed to passive smoking at home. The rate was half that of people who have ever been a smoker.
Although lung function normally declines as we age, the researchers say that the results suggest that air pollution may contribute to this aging process and add to the evidence that exposure to polluted air harms the lungs. COPD, which causes inflammation in the lungs and a narrowing of the airways, making breathing difficult, is estimated to be the third leading cause of death worldwide, with the rate of COPD deaths also expected to increase over the next ten years.
Study author Anna Hansell commented on the study saying, "In one of the largest analyses to date, we found that outdoor air pollution exposure is directly linked to lower lung function and increased COPD prevalence. We found that people exposed to higher levels of pollutants had lower lung function equivalent to at least a year of aging.
"Worryingly, we found that air pollution had much larger effects on people from lower income households. Air pollution had approximately twice the impact on lung function decline and three times the increased COPD risk on lower-income participants compared to higher-income participants who had the same air pollution exposure."
"However, further research is needed to investigate the differences in effects between people from lower- and higher-income homes."