Health effects or risk estimates that are expressed as total-population averages do not represent differences across vulnerable sub-populations. An increase in air pollution exposure that produces a small shift in overall risk may conceal more substantial impacts on a small proportion of vulnerable persons. The implication is that health benefits of pollution reduction – or the effects of increased pollution – are likely to be unevenly distributed within a population. While the use of total-population risks is a valid approach for public health protection, it is increasingly recognized that more attention on vulnerable groups is necessary.
Certain characteristics, commonly age and underlying disease, have been used to define susceptible individuals or populations in epidemiological and other studies of air pollution health impacts. Measures of socio-economic status and other, mostly exposure-related factors such as outdoor activity have also been considered. These can also be thought of as factors that characterise vulnerability to air pollution, but have not been explored in that context.
In this report, information related to susceptibility, exposure and social-economic factors is drawn from the literature to describe vulnerability to air pollution-associated health effects. Population characteristics and factors that contribute to vulnerability are identified and discussed. Their inter-relationships are shown, and the importance of considering their influence in assessing differential risks is underscored. Notably, for populations vulnerable largely due to the physiological aspects of age, exposure-related and social factors may have a significant role and can be more amenable to prevention. Developing a better understanding of population vulnerability can inform future research and action plans. Extension of this work has implications for development of wider, more targeted and more efficient policy measures to reduce health impacts of air pollution.