Characterizing Black Carbon Sources and the Impacts of Open Waste Burning

Open waste burning (OWB) is a widespread practice in many low- and middle-income countries and a significant source of harmful air pollutants, including black carbon (BC), which adversely affects human health and contributes to climate change. Despite these impacts, OWB remains one of the least monitored sources of air pollution. Many existing assessments of environmental and health impacts of OWB rely on emission-based models that depend on multiple assumptions and are therefore subject to substantial uncertainty. Conversely, laboratory-based source apportionment approaches require advanced and costly instrumentation that is often unavailable in under-monitored settings. Consequently, the impacts of OWB on ambient air quality, personal exposure, and human health remain poorly understood. This research aimed to address these evidence gaps by applying practical, medium-cost approaches to investigate the environmental and health impacts of OWB in Blantyre, Malawi, a city with lack of air quality data. This thesis integrated four strands of field-based research. First, a context-appropriate approach was developed to identify local BC sources using the MA200 micro-aethalometer. Controlled field experiments were conducted to establish absorption Ångström exponent (AAE) ranges for fossil fuel and biomass burning sources. Second, this approach was combined with mobile and stationary monitoring to characterize spatial and diurnal patterns of BC concentrations and sources across planned and unplanned neighbourhoods and major roads in Blantyre. Third, personal BC exposure from domestic OWB was quantified for the first time through real-time monitoring of burners and non-burners within the same households, with exposure patterns linked to burning activities. Finally, health impacts were assessed among the population most directly and extremely exposed to OWB: informal waste pickers (IWPs) at Malawi's largest dumpsite, Mzedi. The results show that BC concentrations in Blantyre are comparable to those reported in larger and more densely populated cities in sub-Saharan Africa, driven by multiple sources including OWB. While the contribution of OWB to city-wide ambient BC could not be quantified, individuals directly involved in waste burning and informal waste picking experienced markedly higher personal exposures, revealing a pronounced exposure gradient across population groups and microenvironments. Despite relatively limited evidence of overt respiratory impairment among IWPs, cumulative duration of work at the dumpsite was associated with reduced lung function, suggesting potential long-term health implications of chronic exposure. Overall, the findings highlight OWB as a critical determinant of extreme and inequitable personal exposure and demonstrate that context-adapted monitoring approaches can generate robust evidence to inform targeted air quality and public health interventions in data-scarce settings.