Variability of Airborne Microbial Communities and Associations with Organic Pollutants in African Air Particulate Matter Across Land-Use Types

Abstract

Exposure to particulate matter (PM) is a major global health concern, yet the potential relationships between its chemical and microbial components remains poorly understood, particularly in rapidly urbanizing, understudied settings. This study presents an integrated assessment of polycyclic aromatic hydrocarbons (PAHs), nitrated PAHs (NPAHs), bacteria, and fungi in both fine (PM2.5) and coarse (PM10) aerosols across urban, roadside, and rural sites in sub-Saharan Africa, with a focus on Rwanda across dry and wet seasons. Microbial analysis revealed that the richness and community structure of the airborne bacterial and fungal communities varied with land-use type, linked with PAH/NPAH abundance, PM size fraction, and season. Spearman correlation coefficient confirmed that bacterial communities were more strongly associated with PAH and NPAH compounds, whereas fungal communities were shaped primarily by environmental factors. One bacterial genus, Sphingobium, exhibited evidence of selective enrichment within the PAH rich PM2.5 size fraction, highlighting the potential for direct interaction between the biological and chemical compositions in air. We provide a critical baseline for African cities where air quality data are scarce. Current air quality standards, which prioritize chemical thresholds, overlook the biological burden carried by PM.