Urban Pollution Burden in Sub-Saharan African (SSA) Cities: Characterizing PM_2.5, PM₁₀, and Black Carbon in Two Contrasting Environments in Accra, Ghana

Fine and coarse particulate matter (PM_2.5, PM₁₀) and black carbon (BC) pose significant health risks in rapidly urbanizing cities in low- and middle-income countries, particularly in sub-Saharan Africa. However, studies pertaining to their local impacts and disparities are less understood in these cities. This study modeled PM_2.5, PM₁₀, and BC differences in Accra, Ghana, to separate the impacts of local urban emissions from regional weather patterns and identify the specific drivers of pollution. Using reference-grade monitors, we conducted year-long, concurrent measurements of PM_2.5, PM₁₀, and BC at two sites with distinct land-use characteristics: a busy high-density urban core and a low-density urban backgroundThe results show significant urban pollution burden exceeding recommended guidelines for PM_2.5 and PM₁₀, with annual mean concentrations at the urban core site higher than the background site for PM_2.5 (38.6 vs 27.9 μg m^–3), PM₁₀ (99.3 vs 71.0 μg m^–3), and BC (7.5 vs 3.7 μg m^–3), underscoring the impact of local traffic and residential activities. A strong seasonal variation was also observed, with pollutant levels increasing significantly at both sites during the dry-Harmattan period (November–March) due to the transport of Saharan dust. Analysis of pollutant ratios (PM_2.5/PM₁₀ and BC/PM_2.5) confirms a shift in aerosol type: coarse mineral dust dominates during the dry-Harmattan, while fine particles from local combustion sources are more prominent in the wet season. Using linear mixed effects models with PM₁₀, the dry season, and daytime (06:00–17:59) as baseline variables, we demonstrated that PM₁₀ pollution constitutes a persistent pollutant more than PM_2.5 and BC at the high-density site, remaining significantly elevated (∼70% excess) regardless of the season. This study provides quantitative evidence of the dual impact of local land-use sources and regional weather on Accra’s air quality. Our findings highlight the need for a two-track management approach that addresses both hyper-local emission sources and the large-scale impacts of seasonal phenomena like the Harmattan.