This paper presents the relations established between urban morphology and variations in observed air quality within a city centre. A dataset from four monitoring stations in a medium-sized city was collected and clustered by the amount of traffic-generated air pollutants. For each cluster, the relationship between the configuration of the open spaces and average PM10 concentration was established. Results show the impact of urban geometry on the outdoor pollutant concentration, concluding that increasing Sky View Factor and Ratio of Open Spaces lead to a decrease in the PM10 concentration.