Health impact assessment of air pollution: providing further evidence for public health action.

Many epidemiological studies have demonstrated the importance of air pollution as a risk factor and characterised dose-response relationships between health endpoints and pollutants. The association between particulate matter (PM) and health is generally regarded as causal, and a nonthreshold linear relationship with, for example, mortality and hospital admission has been observed in several settings. The ubiquitous PM air pollution is likely to have a large overall impact on human health, even if risks are relatively small. There have recently been a large number of papers reporting quantitative estimations of the health impact of PM on health, as measured by the proportion of excess events that are attributable to PM exposures in the general population, mainly in industrialised countries. For example, in the eight largest Italian cities it has been estimated that concentrations beyond 30 microg x m(-3) are responsible for about 3,500 extra deaths per year. A similar study has been carried out for France, Austria and Switzerland. These evaluations fill a knowledge gap between the laboratory and clinical studies on the pathophysiological mechanisms, the epidemiological research on the nature and strength of the association at the population level, and the risk management needs for developing appropriate preventive policies. Some limitations in the methodology deserve further research, however health impact assessment type studies are informative and effective tools of communication with the general public and policy makers.