December 9th, 2013

European Air Pollution Standards May Need to be Strengthened

A large new analysis published in the Lancet has found a strong association between long-term exposure to air pollution and the risk of dying. The results suggest that European standards for air quality may need to be strengthened.

The European Study of Cohorts for Air Pollution Effects (ESCAPE) analyzed data from 22 European  studies, including 367,251 participants followed for an average of 13.9 years. Nearly 30,000 deaths from natural causes occurred during followup. ESCAPE is the first large multicenter study to examine long-term exposure to air pollution and mortality across many different European settings. The authors adjusted their findings to account for a broad range of confounding factors, including smoking, socioeconomic status, physical activity, education level, and body-mass index.

Overall, the investigators found a consistent 7% increase in mortality (hazard ratio 1.07, CI 1.02-1.13) for every 5 μg/m3 increase in air pollution (particulate matter with diameters smaller than 2·5 μm). This association remained significant even when air pollution levels were well below the existing European Commission air quality standards, which uses a threshold of 25 μg/m3. The WHO and the U.S. — with thresholds at 10 and 12 25 μg/m3, respectively — have considerably stronger standards.

“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,” explained the study leader Rob Beelen (Utrecht University, NL), in a Lancet press release. “Our findings support health impact assessments of fine particles in Europe which were previously based almost entirely on North American studies.”

One striking and unexplained finding was that the increase in mortality was found only in men. The Lancet publication focuses on overall natural-cause mortality. A second paper will focus on cause-specific results, but the authors briefly report that they found significant increases in the incidence of lung cancer and stroke mortality, but, surprisingly, not for mortality from ischemic heart disease or respiratory disease.

In an accompanying comment, Jeremy Langrish and Nicholas Mills write that “despite major improvements in air quality in the past 50 years” the new study highlights “the continuing effects of air pollution on health. 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.”



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