Exposure to air pollution has long been associated with the development of serious health issues, such as lung cancer. The European Union set air quality limits, stating that air pollution must not exceed 25 micrograms per cubic meter. But new research suggests exposure to air pollution can kill at levels well below these limits.
To reach their findings, published in the Lancet, a team of international researchers reviewed data spanning almost 20 years from 367,251 residents of large cities over 13 European countries.
The data was taken from 22 studies that were part of the European Study of Cohorts for Air Pollution Effects (ESCAPE).
Using land-regression models to estimate residents' air pollution exposure, the researchers linked the average annual air pollution concentrations of nitrogen oxides and particulate matter to their home addresses.
They also monitored the residents' traffic density on their nearest road, as well as total traffic on all major roads within 100 meters.
The participants were followed-up for an average of 13.9 years. During that time, 29,076 died from natural causes.
Death risk increased even with low exposure
From the analysis, the researchers found that the greatest health threat was from long-term exposure to fine-particle air pollution with a diameter of less than 2.5 micrometers (PM2.5), even within concentrations that were below the European Union (EU) limit of 25 micrograms per cubic meter (25 µg/m3).
Furthermore, it was found that for every increase of 5 µg/m3 in annual exposure to PM2.5, the risk of dying from natural causes increases by 7%.
Commenting on their research, the investigators say:
"Our findings show that long-term exposure to fine particulate air pollution is associated with natural-cause mortality, even at concentration ranges well below the present European annual mean limit value."
They say their findings were significant, even after adjusting for factors such as smoking status, socioeconomic status, physical activity, education level and body mass index (BMI).
EU limits 'should move toward WHO recommendations'
The current World Health Organization (WHO) guideline is 10 µg/m3 - significantly lower than the EU limit.
The investigators say their findings support the idea that significant health benefits can be achieved if the EU moves toward the WHO target.
Commenting in an editorial linked to the study, Jeremy P. Langrish and Nicholas L. Mills, of the University of Edinburgh in the UK, agree that the EU limits should be reviewed:
"These data, along with the findings from other large cohort studies, suggest that further public and environmental health policy interventions are necessary and have the potential to reduce morbidity and mortality across Europe.
Movement towards more stringent guidelines, as recommended by WHO, should be an urgent priority."
Medical News Today recently reported on a study suggesting that exposure to air pollution during pregnancy may increase the risk of low birthweight babies.