The opposite phenomenon is observable for a number of Polish LUZs. Yet, Madrid experiences high levels of concentration for each type of pollutant as opposed to Estonia which records a low level of pollution. Figures 3, 4 and 5 highlight the importance of understanding the differences across pollutants as some areas are very affected by one pollutant and much less by others. Furthermore, Table 2 below shows that the correlations between pollutants do not exceed 0.5 which is relatively low. Derived from CORINE Land Cover (CLC), UMZ data covers the whole EU-27 at 200-meters resolution for those urban areas that are considered to contribute to urban tissue and function. Geospatial data on land-use for each urban area are obtained by superimposing the LUZ boundaries and the UMZ spatial data, for each LUZ, data collected on urbanisation allow the study of different components of urban form: number of fragments, share of artificial area, share of agricultural area, share of wetland, share of forest area, population density, population decentralisation (with respect to the core city) and the LUZ surface.