Meteorological drivers of ambient PM_2.5 pollution at urban traffic intersections in Accra, Ghana

Accra, Ghana, faces deteriorating ambient air quality due to rapid urbanization and heavy vehicular traffic. However, site-specific influence of meteorological drivers on PM_2.5 at pollution hotspots remains limited. PM_2.5 levels and their association with meteorological parameters at nine traffic hotspots were evaluated. Ambient PM_2.5 concentrations were monitored to capture both harmattan and non-harmattan seasons, using an Aeroqual Ranger portable dust monitor. Daily meteorological data, including temperature, relative humidity, wind speed, and rainfall, were obtained from automatic weather stations operated by the Ghana Meteorological Agency. Pearson correlation analysis was used to evaluate the relationship between PM_2.5 and meteorological parameters. Median PM_2.5 concentrations of 54.90 μg/m³ at high-density, 34.26 μg/m³ at commercial/business, and 16.75 μg/m³ at low-density traffic areas were recorded. These values substantially exceed the WHO 24-h guideline of 15 μg/m³. Ashaiman (median = 54.90 μg/m³) is the most polluted traffic site, due to severe congestion, aged vehicles, and extensive roadside commercial activities. Correlation analysis revealed that temperature exhibited a significant positive association with PM_2.5 (r = 0.353, p < 0.01). Conversely, rainfall, wind speed, and relative humidity during the non-Harmattan season showed negative correlations, consistent with wet deposition and pollutant dispersion. During the Harmattan season, wind speed showed a weak positive association with PM_2.5 (r = 0.079, p = 0.450), attributed to localized dust resuspension and dry atmospheric transport. The findings demonstrate that while meteorological parameters influence PM_2.5, the dominant factor remains localized vehicular emissions at traffic hotspots. This underscores an urgent need for emission-focused policies and targeted interventions to protect the health of exposed urban populations in Accra.