Air pollution and life expectancy: is there a relation?

The great smog disasters of the past have made clear that air pollution can kill people in a matter of days: extremely high concentrations of air pollution building up under conditions of low wind speed and stable atmospheric conditions have been associated with excess deaths in the Meuse Valley, Belgium (1930); Donora, PA, United States (1948); and London, United Kingdom (1952). In the developed market economies, great efforts have since been made to curtail air pollution related to the use of fossil fuels such as coal and oil, and exposures to substances such as SO2 and soot have been dramatically reduced. For a while it was thought that ambient concentrations of air pollution had become so low as to have no discernible influence on mortality or morbidity in the population any more. However, a series of recent studies have shown that even at low concentrations of substances-such as ozone and fine particulate matter in air-day to day variations in mortality, respiratory and cardiovascular hospital admissions, symptom exacerbations among asthmatic patients, lung function in schoolchildren, etc are still associated with day to day changes in concentrations of air pollution.' Although such findings are important in their own right, they do not directly prove that long term exposure to air pollution at present levels in the developed market economies increases the prevalence of (chronic) diseases in the population, possibly leading to decreased survival and hence, reduced life expectancy: the associations found between day to day variations in mortality and air pollution may, for example, represent a "harvesting" effect-that is, an advancement of death by a few days or weeks in subjects already about to die from other causes anyway. Clearly, such effects would not lead to discernible effects oflong term exposure to air pollution on life expectancy in the population. There is some evidence, however, that long term exposure to relatively low concentrations of ambient air pollution leads to a measurable reduction of survival in the population. In this paper, I briefly review the evidence, focusing on effects of airborne particulate matter, and I provide a simple estimate of the effect that long term exposure to air pollution may have on life expectancy, based on this evidence.