This paper employs computational fluid dynamics (CFD) simulations, validated by experimental data, to examine the impact of building configurations on urban airflow and the dispersion of vehicular CO emissions from a ground-level source. The study focuses on two-dimensional (2D) symmetric, step-up and step-down canyons characterized by different building height ratios (BHR) which may be defined as the ratio of height of the downwind building to that of an upwind building (BHR = 1, 0.5, and 2). The findings suggest that the step-down configuration leads to more adverse wind conditions and poorer dispersion of pollutants compared to symmetric and step-up configurations. Furthermore, concentrations tend to be elevated on the leeward side of the wall in the case of step-up and symmetric canyons, whereas the results show the opposite trend for step-down canyons. The findings mentioned above are valuable in comprehending how building configurations can impact both the wind environment and the level of pollutant exposure risk for pedestrians and residents living near roads.