Figure 1.

Map of the Greater Accra Metropolitan Area (GAMA) with locations of ‘fixed’ and ‘rotating’ sites with annual concentrations of (A) NO and (B) NO₂. The colors of NO₂ concentrations indicate comparison to the new World Health Organization (WHO) annual air quality guideline of 10 μg m⁻³. The concentrations at the fixed sites represent annual mean values, and the rotating sites represent season-adjusted mean values (i.e. an estimated annual means). Major and secondary road network were from OpenStreetMap [27] (downloaded in 2019).