Air pollution ages our lungs faster and increases the risk of developing chronic obstructive pulmonary disease (COPD). While lung function declines typically as we age, new research now shows that air pollution contributes to the aging process.
The large study of 303,887 individuals, aged 40-69 years, shows that outdoor air pollution exposure is directly linked to lower lung function and increased COPD prevalence. People exposed to higher levels of pollutants had lower lung function equivalent to at least a year of aging, says the study, which adds to the growing evidence that breathing in polluted air harms the lungs.
COPD is a long-term condition, which is linked to reduced lung function. It causes inflammation in the lungs and a narrowing of the airways, making breathing difficult. According to the Global Burden of Disease (GBD) project, COPD is the third leading cause of death worldwide, and the number of global COPD deaths is expected to increase over the next ten years.
The study also found that for each annual average increase of five micrograms per cubic meter of particulate matter (PM2.5) in the air that a person was exposed to at home, the associated reduction in lung function was similar to the effects of two years of aging.
“Ambient concentrations of particulate matter and nitrogen dioxide air pollution were associated with lower lung function and increased COPD prevalence. Stronger (adverse) lung function associations were seen for males, individuals from lower income households, and ‘at-risk’ occupations, and higher COPD associations for obese, lower income, and non-asthmatic participants," says the findings.
It adds, “We found significant reductions in lung function, even at relatively low levels of ambient PM2.5, thereby echoing the need for more actions to be taken to control air pollution,” says the research team.
According to the World Health Organization (WHO), PM is a standard proxy indicator for air pollution, affecting more people than any other pollutant. Particles with a diameter of 2.5 microns or less are the most damaging as they can penetrate the lung barrier and enter the blood system. Chronic exposure to particles contributes to the risk of developing cardiovascular and respiratory diseases, as well as lung cancer.
The types of pollutants the researchers examined for their study included particulate matter (PM10), fine particulate matter (PM2.5) and nitrogen dioxide (NO2), which are produced by burning fossil fuels from the car and other vehicle exhausts, power plants and industrial emissions.
According to the WHO, outdoor air pollution is estimated to have caused 4.2 million premature deaths worldwide in 2016. “This mortality is due to exposure to small particulate matter of 2.5 microns or less in diameter (PM2.5), which cause cardiovascular and respiratory disease, and cancers,” says WHO.
For the current study, the researchers used a validated air pollution model to estimate the levels of pollution that people were exposed to at their homes when they enrolled in the UK Biobank study. Participants had to answer detailed health questionnaires as part of the data collection. Lung function was measured using spirometry tests, which were performed by medical professionals at Biobank assessment centers at enrolment between 2006 and 2010.
Further, the research team conducted multiple tests to assess how long-term exposure to higher levels of the different air pollutants was linked to changes in the participants' lung function. The participants' age, sex, body mass index (BMI), household income, education level, smoking status, and exposure to second-hand smoke were also accounted for in the assessment.
Among participants living in areas with PM2.5 concentrations above the WHO annual average guidelines of ten micrograms per cubic meter, COPD prevalence was four times higher than among people who were exposed to passive smoking at home, and prevalence was half that of people who had been smokers, the findings state.
The current EU air quality limit for PM2.5 is 25 micrograms per cubic meter, which is higher than the levels that were found as being linked to reduced lung function in the study.
The research team also observed considerably stronger associations for lung function and COPD among individuals from lower income households. They found that 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.
“The greater vulnerability of lower-income individuals to the respiratory health effects of air pollution exposure is in line with previous studies, and is likely due to numerous factors, including more childhood respiratory infections, poorer housing conditions and indoor air quality, poor nutrition and occupational exposures,” says the paper.
The international team included researchers from the Research Institute of the McGill University Health Centre (Montreal), University of Leicester (UK), Imperial College London, and King's College London, among others. They are now conducting further studies to look at whether genetic factors interact with air pollution and its impact on health.
The study was published in the European Respiratory Journal.