Particulate air pollution and health inequalities: a Europe-wide ecological analysis

Background
Environmental disparities may underlie the unequal distribution of health across socioeconomic groups. However, this assertion has not been tested across a range of countries: an important knowledge gap for a transboundary health issue such as air pollution. We consider whether populations of low-income European regions were a) exposed to disproportionately high levels of particulate air pollution (PM10) and/or b) disproportionately susceptible to pollution-related mortality effects.

Methods
Europe-wide gridded PM10 and population distribution data were used to calculate population-weighted average PM10 concentrations for 268 sub-national regions (NUTS level 2 regions) for the period 2004–2008. The data were mapped, and patterning by mean household income was assessed statistically. Ordinary least squares regression was used to model the association between PM10 and cause-specific mortality, after adjusting for regional-level household income and smoking rates.

Results
Air quality improved for most regions between 2004 and 2008, although large differences between Eastern and Western regions persisted. Across Europe, PM10 was correlated with low household income but this association primarily reflected East–West inequalities and was not found when Eastern or Western Europe regions were considered separately. Notably, some of the most polluted regions in Western Europe were also among the richest. PM10 was more strongly associated with plausibly-related mortality outcomes in Eastern than Western Europe, presumably because of higher ambient concentrations. Populations of lower-income regions appeared more susceptible to the effects of PM10, but only for circulatory disease mortality in Eastern Europe and male respiratory mortality in Western Europe.

Conclusions
Income-related inequalities in exposure to ambient PM10 may contribute to Europe-wide mortality inequalities, and to those in Eastern but not Western European regions. We found some evidence that lower-income regions were more susceptible to the health effects of PM10.