The purpose of this paper is the assessment of the environmental air pollution in a very densely inhabited area in the southern Italy, which is characterised by serious general contamination. Because the air pollution may have an impact on human health, this area was identified in 1998 as a National Interest Priority Site and comprises a large part of agricultural lands belonging to over 60 municipalities between Naples and Caserta provinces. This study characterises the air pollution affecting this area by estimating the total annual emissions of the major pollutants (CO, NOX, VOC, PM and heavy metals) and showing their municipal spatial disaggregation. In this study a bottom-up methodology was employed, then focusing at regional level instead of national and comprising local and specific parameters. The pollutants emitted from several sources in the area under investigation were obtained by direct measurements of the principal industrial point sources, whereas the emissions from diffuse sources were calculated on the basis of local activity indicators and specific emission factors concerning the relevant activities in this area. The results obtained in this research have identified local critical factors.