Outdoor air pollution: assessing the environmental burden of disease at national and local levels
Environmental burden of disease series, No. 5
In a recent estimate, outdoor air pollution was found to account for approximately 1.4% of total mortality, 0.5% of all disability-adjusted life years (DALYs) and 2% of all cardiopulmonary disease (World Health Report 2002). This guide outlines a method for quantifying selected health impacts associated with outdoor air pollution. Such an estimate can be performed at the level of a country or city, according to locally available exposure and health data, and can be used as input to decision-making regarding for example transport options or standard setting in air quality.
The exposure variable for air pollution used in this guide is particulate matter (PM) measured as either PM10 or PM2.5 (i.e. PM less than 10 μm or 2.5 μm in diameter, respectively). Population exposure is characterized by exposure concentrations and the numbers of people exposed at the various exposure levels. Concentrationresponse functions from the epidemiological literature are then applied to the exposed population. These functions relate ambient PM concentrations to cases of premature mortality, and enable the attributable risk to be calculated. The following health outcomes are considered in this guide: adult cardiovascular diseases and lung cancer associated with long-term exposure to PM2.5, all-cause mortality for all ages associated with short-term exposure to PM10, and infant and childhood mortality from respiratory diseases associated with PM10 exposure. Outdoor air pollution has been associated with many more health outcomes, for example asthma exacerbation. However the evidence is currently not sufficient to make recommendations for quantitative methods that are applicable at global level.
The guide reviews the scientific evidence for the effects of air pollution on both mortality and morbidity. It summarizes the steps for calculating the disease burden, discusses associated uncertainties and illustrates the method using a step-by-step numerical example for Bangkok, Thailand.