Research and analysis

COMEAP: long-term exposure to air pollution: effect on mortality

A report by the Committee on the Medical Effects of Air Pollutants (COMEAP).

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The Committee on the Medical Effects of Air Pollutants (COMEAP) produced in 2001 a report on the long-term effects of particulate air pollution on mortality. Research in this field has progressed rapidly since then and we present in this report a summary of the new evidence and quantitative estimates of the impact of the longterm effects of particulate pollution on mortality.

We have looked in detail at the evidence linking long-term exposure to air pollutants and effects on mortality. In doing this we have assessed the possible effects of a range of factors that may affect or confound the reported associations. Whilst in this report we focus on effects on mortality, the effects of long-term exposure to air pollution on morbidity and the effects of short-term exposure to air pollution, including effects on infants, will be dealt with separately and are not covered by this report.

We are left with little doubt that long-term exposure to air pollutants has an effect on mortality and thus decreases life expectancy. In this report we have recommended coefficients which, when used in conjunction with methods developed for the Department of Health and the European Commission by the Institute of Occupational Medicine, will allow calculation of the potential impact on mortality and life expectancy of specified reductions in concentrations of air pollutants. We have not undertaken these calculations as part of the work reported here. These calculations will be undertaken at a later stage and presented as a supplementary paper to this report. This work will not involve the evaluation of specific policy interventions.

The evidence base regarding the effects of long-term exposure to air pollutants has strengthened since our 2001 report. This strengthening comprises both extensions to, and reanalysis of, the results of the studies we looked at in 2001 and publication of a number of European cohort studies and studies of the effects of policy initiatives. The evidence as a whole points strongly to an association between long-term exposure to particulate air pollution and effects on mortality. The evidence also points to PM2.5 1 as the most satisfactory index of particulate air pollution for quantitative assessments of the effects of policy interventions. The best studied effects and those which we recommend for use in quantification exercises are effects on all-cause mortality, on cardiopulmonary mortality and on lung cancer mortality.

Evidence relating to the possible effects of long-term exposure to the common air pollutant gases (sulphur dioxide, nitrogen dioxide and ozone) is less well developed and we do not make any recommendations in favour of quantifying the effects of long-term exposure to these compounds. This may become possible if more evidence accumulates.