Beyond smoke: culturable airborne bacteria associated with informal waste burning in peri-urban South Africa.

Introduction: Informal waste burning is an established source of particulate matter and hazardous combustion emissions in many low- and middle-income settings, yet its potential contribution to biological airborne exposure remains poorly characterized. This study investigated culturable airborne bacteria in active informal waste-burning environments in Hammanskraal, South Africa, and examined their spatial variability and potential relevance to environmental exposure. Methods: A cross-sectional exploratory field investigation was conducted at three active informal waste-burning sites and one non-burning comparison site. Active air samples were collected using a Sampl'Air Pro impactor onto Tryptic Soy Agar at approximate distances of 25, 50 and 100 m from visible combustion areas. Culturable airborne bacterial concentrations were quantified as colony-forming units per cubic meter (CFU/m Results: The highest culturable airborne bacterial concentrations occurred at active waste-burning sites, although concentrations varied substantially among sites. Burn-site concentrations ranged from 91 CFU/m Discussion: Active informal waste-burning environments contained viable culturable airborne bacteria, with markedly elevated concentrations observed at some burning sites relative to the non-burning comparison environment. Distance from active combustion alone did not explain the observed spatial variability; site-specific factors including combustion intensity, plume behavior, environmental disturbance and local meteorology may influence short-term bioaerosol occurrence and warrant investigation using more highly replicated designs. These findings identify viable culturable bacteria as an under-characterized component of informal waste-burning environments and provide a basis for future integrated studies of environmental occurrence, human exposure and potential health relevance.