Prolonged exposure to tiny particles of soot or dust found in traffic fumes and industrial emissions may be more deadly below current European Union (EU) air quality limits than previously thought, according to new research examining two decades of data from over 360 000 residents of large cities in 13 European countries.
The study, published in The Lancet, estimates that for every increase of 5 microgrammes per cubic metre (5 µg/m3) in annual exposure to fine-particle air pollution (PM2·5), the risk of dying from natural causes rises by 7%.
“A difference of 5 µg/m3 can be found between a location at a busy urban road and at a location not influenced by traffic”, explains study leader Dr Rob Beelen from Utrecht University in the Netherlands. “Our findings support health impact assessments of fine particles in Europe which were previously based almost entirely on North American studies.”
Using data from the European Study of Cohorts for Air Pollution Effects (ESCAPE), the investigators pooled data from 22 cohort studies including 367 251 people. Annual average air pollution concentrations of nitrogen oxides and particulate matter were linked to home addresses using land-regression models to estimate exposures. Traffic density on the nearest road and total traffic load on all major roads within 100m of the residence were also recorded.
Among the participants, 29,076 died from natural causes during the average 13·9 years of follow up.
The results showed that long-term exposure to fine particles with a diameter of less than 2·5 micrometres (PM2·5) posed the greatest threat to health even within concentration ranges well below the limits in current European legislation.
The association between prolonged exposure to PM2·5 and premature death remained significant even after adjusting for a wide range of confounding factors such as smoking status, socioeconomic status, physical activity, education level, and body-mass index.
The researchers also noted an effect of gender—with PM2·5 associated with excess mortality in men but not in women.