Unequal exposure: spatio-temporal and structural determinants of personal PM2.5 exposure in three sub-Saharan African geographies-the Gambia, Kenya, and Mozambique.

Abstract

Background: Personal exposure to fine particulate matter (PM_2.5) 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 PM_2.5 monitoring 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 PM_2.5 was measured at nearby health facilities.

Results: Across 3,190 person-days, daily median PM_2.5 was 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 (R ² 0.01-0.56; slopes <1).

Conclusion: Personal PM_2.5 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.