Air pollution is a major health environmental risk. In particular, daily exposure to high concentrations of microscopic atmospheric particles (PM10 and PM2.5), is related to increased mortality and morbidity. Many countries are concerned about this issue and have extensive monitoring networks and specific air-quality legislation to establish limit values for PM concentration. In Argentina, very few cities have carried out continuous measurements of air quality. In particular, Buenos Aires city (34.4°S, 58.3°W) has three monitoring stations located at different locations. Buenos Aires and its metropolitan area is the most populated area in the country (12.806.866 inhabitants in 2010 Census). Though ground-based stations provide accurate PM concentration values, they are strongly influenced by local emission sources and do not characterize completely the actual spatial distribution of pollutants in the city. So, this type of monitoring is insufficient to assess the actual level of population exposure. Satellite-based aerosol optical depth (AOD) dataset represent a valid alternative to fill these observational gaps. Several satellites offer AOD products, being the dataset from the MODIS sensors on board TERRA and AQUA (NASA) spacecrafts among the most used for regional air quality studies. In this work, the MODIS 3 Km x 3 Km AOD retrievals for 2014 were employed to evaluate the spatio-temporal variation of atmospheric aerosols over Buenos Aires metropolitan area in a year period. The MODIS dataset was  validated using as ground truth the AOD dataset available from the AERONET CEILAP station (34.5°S,58.5°W) (https://aeronet.gsfc.nasa.gov/). In order to evaluate how well satellite data represent surface measurements, the seasonal AOD maps retrieved from MODIS data were compared with PM measurements at the particular locations of ground-based stations. In this way, the spatio-temporal variation during a whole year of atmospheric aerosols over the largest urban area in Argentina was determined.