Health Impact Assessment of long-term exposure to particulate air pollution: methodological and practical considerations.

Abstract

Background Quantitative Health Impact Assessment (HIA) aims to create predictions of the impacts on health of changes in the human environment. Typically, this requires the assessor to bring together data on the environmental changes envisaged, the populations affected, and the health outcomes likely to be impacted by the changes. At the heart of the calculations will be a concentration-(or exposure- or dose-)response coefficient or function, quantifying how environmental change is expected to increase or decrease the rate of the health outcome in the population. Any HIA requires clear statements of the question(s) being asked: are we interested in quantifying the current health burden against a (counterfactual) cleaner scenario; or is our focus the future effects of policy changes; or perhaps both? Methods It’s been widely accepted that particulate air pollution affects mortality: although other health effects are also related, mortality dominates multiple-outcome assessments. Recent evidence has accumulated that points to risks for cardiovascular death in particular. HIAs based on mortality usually rely on the application of life-table methods to predict changes in life expectancy, but burden calculations require many assumptions, and predictions about the future many more. These, and the availability of input data for calculations, will inform the design of a HIA. These issues have arisen in EU projects such as CAFE and HEIMTSA; in work for the UK government’s Committee on the Effects of Air Pollutants (COMEAP) e.g. for their report of 2010; and as part of the English health service’s localisation agenda. Many of the issues involved will be illustrated in detail in the context of case studies of the health effects of transport policies on cities, within the current EU project TRANSPHORM.