The dataset contains files with environmental measurements that were obtained from ad-hoc targeted field campaigns in six ICARUS cities (i.e. Athens, Thessaloniki, Madrid, Stuttgart, Ljubljana, Brno). The dataset is organized in a series of subfolders each one named according to the city name and which includes all the data measured in that specific ICARUS city. Each of these subfolders contains several files which include: the location where the measurements were carried out, the time stamp, the air pollutant concentrations measured (NOx, SO2, CO, O3) as well as the results of the chemical analysis of the PM2.5 samples collected (PAHs, ions, heavy metals, OC/EC). A further file named “GHGs Ground sampling.xlsx” reports the GHGs (CO2, N2O, CH4, SF6) concentration levels measured in the different cities.