Inter-municipal commuting and impact of PM10 on mortality in the Lombardy region, Italy

Background. In evaluating the impact of air pollution on human health, the assumption of a static population is usual. However, daily commuting between home and work/school place may influence the impact estimate in the presence of different levels of exposure over the area of interest. Mobility in the Lombardy region is important, with the largest percentage of resident population which moves daily to its job or school place among the Italian regions. Moreover the air pollution levels are heterogeneus, with very high concentrations in the Po river plain. Aims. Our aim was to quantify the short term impact of PM10 exposure on mortality in the Lombardy region during 2007, accounting for inter-municipality school and job commuting. Methods. We used inter-municipality commuting flows from the 2001 census to estimate the yearly number of attributable deaths in each municipality. We assumed that the commuters were exposed to the PM10 levels of the municipality where they work or study for one third of their ti...