smog

Living near a busy road can kill you

Early April saw some unusually smoggy days across much of Western Europe, resulting in widespread media attention to air pollution.
(See, for example, here, here and here.) On one day, air quality in some parts of London was worse than in Beijing. Further attention has been drawn to the issue by a number of recent official reports, including one from the World Health Organisation, which has declared that air pollution is now the world’s biggest single environmental threat to health.

As has been noted, media coverage can give a misleading picture of the health risks of air pollution. Coverage tends to focus on short-term peaks, such as those seen recently in Western Europe, but the health risks of air pollution are primarily related to long term exposure, and show no ’safe threshold’ effect. Elevated baseline levels of pollution are thus more of a problem than occasional peaks.

There’s another important aspect of air pollution that often goes unnoticed; small geographical differences can have a marked effect on exposure to air pollution and thus on risk of adverse health effects. For example, living near a busy road appears to substantially increase air pollution-related mortality. A study published last year in the Lancet (press summary here) investigated the effects of very local differences in air quality on mortality by pooling 22 European cohort studies. The investigators found that an increase in average annual fine particulate (PM2.5) exposure of 5 µg/m3 was associated with a 7% increase in the risk of dying from all natural causes. This is approximately the difference between living on a busy urban road and living in a traffic-free area. The finding was robust in the face of correction for various possible confounding factors. Continue reading

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