High concentrations of the ambient particulate matter remains a concern on the South African Highveld, particularly in densely populated low-income settlements. These areas have several local emission sources that contribute to poor air quality and are often located close to industrial and other urban areas. The local sources vary in magnitude, space, and time. In South Africa, little has been done to assess the impacts of spatiotemporal variability on the credibility of using isolated ambient observations for regulatory purposes. This study aims to evaluate the intra-urban variability of ambient PM2.5 concentrations in a dense, low-income community. Ambient fine particulate matter (PM2.5) in distinct microenvironments of KwaZamokuhle were simultaneously measured at 4 sites between March and June 2018. These measurements were collected using one permanent ambient monitoring station (AMS) and a temporary network of three E-BAM monitors (Site 2, Site 3, and Site 4). The daily PM2.5 concentrations at AMS, Site 2, Site 3, and Site 4 varied from 10 to 86 µg.m-3, 10 to 103 µg.m-3, 11 to 101 µg.m-3, and 9 to 113 µg.m-3, respectively. Extreme PM2.5 concentrations which exceeded the 24h PM2.5 NAAQS of 40 µg.m-3 were seen during the cold period (May and June); meanwhile, the warm period (March and April) recorded relatively lower PM2.5 episodes across different sections of KwaZamokuhle. During May-June, the highest diurnal concentrations of hourly averaged ambient PM2.5 were recorded at Site 4, in a downward sequence, followed by Site 3, Site 2, and AMS. Furthermore, the results showed that across KwaZamokuhle, Site 4 has the highest proportion of households using solid fuels for domestic purposes (cooking and heating) (55%) and the number of informal dwellings (117 households). Therefore, the study highlights the complexity of quantifying ambient air quality in an area where several local emission sources vary in space and time. Attempts to use monitoring data from a single station to assess ambient air quality, quantify human exposure, or evaluate the potential impacts of mitigation strategies in dense, low-income settlements should be done with care.

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Emissions from residential solid fuel burning in densely populated low-income settlements is a significant source of air pollution over the South African Highveld. The area is densely populated and highly industrialized, resulting in high concentrations of pollutants over the area. Although emissions from industrial sources are much larger, exposure to household emissions poses the most significant risk to human health. Interventions aimed at reducing solid fuel burning in low-income settlements on the Highveld have the potential to reduce exposure, but quantifying their true impact remains a challenge. We aimed to estimate the health and associated economic benefits of the regional implementation of thermal insulation as intervention measure in low-income settlements to predict the potential impact on the regional scale. We used a land use type regression model to estimate pre-intervention PM2.5 concentrations over the Highveld and then used sampled post-intervention air quality data from a pilot offset programme to relate changes in air quality to changes in avoided premature mortalities. We estimate that the large-scale implementation of this intervention could result in 143 avoided premature mortalities with an estimated economic benefit of just under ZAR (2011) 341.6 million, equivalent to USD (2011) 49.4 million.