Unequal Exposure: Spatio-Temporal and Structural Determinants of Personal PM2.5 Exposure in Three Sub-Saharan African Geographies – The Gambia, Kenya, and Mozambique

Background
Personal exposure to fine particulate matter (PM₂.₅) in sub-Saharan Africa remains poorly characterised, obscuring the roles of structural inequities, seasonality, and mobility in shaping dose.
Methods
We undertook 5day per season personal PM₂.₅monitoring among 343 parous women in The Gambia, Kenya, and Mozambique, spanning dry and wet seasons. Minute-resolved personal concentrations were aligned with microenvironment, fuel use, occupation, wealth, and meteorology within an integrated exposure assessment framework incorporating microenvironment classification and structural determinants; ambient PM₂.₅ was measured at nearby health facilities. Results
Across 3,190 person-days, daily median PM₂.₅was 10·4 (7·6–14·7) μg/m³ in The Gambia, 8·1 (6·8–9·8) μg/m³ in Kenya, and 10·9 (9·3–13·5) μg/m³ in Mozambique. Episodic spikes were prominent. WHO 24-h health guideline exceedances were strongly seasonal and site-specific (The Gambia: 55·9% dry vs 13·6% wet; Kenya: 8·9% vs 3·7%; Mozambique: 20·9% vs 28·6%). Exposures were higher away from home, with mid-day peaks (≈12:00– 16:00). At home, biomass/coal users had higher medians than LPG/electricity users. Structural gradients were evident, including population density, occupation, and wealth gradients. Ambient–personal concordance was heterogeneous and context-dependent (R² 0·01–0·56; slopes <1).
Conclusion
Personal PM₂.₅ exposure among pregnant women in these three African settings was shaped by season, mobility, household energy, and structural disadvantage. Household clean-fuel transitions remain essential but are unlikely to fully reduce exposure unless complemented by interventions targeting transport corridors, markets, peri-domestic combustion, and other away-from-home exposure environments.