Finally, one final social characteristic we looked at is the unemployment rate. Fig. 7 shows the relation between the population density and the unemployment rate. Briefly, we see that the unemployment rate and the population density are positively correlated. We will interpret those results in the next section. Finally, Fig. 8 is a map of the socio-economic principal characteristics of the municipality, where the polluted zones have been represented in order to conclude about the relation between a polluted area and the corresponding population which live close these sites.