More than 40% of Cape Town’s metropolitan population is exposed to high or very high levels of air pollution, according to a new study by the University of Cape Town (UCT) which has produced the first high-resolution map of air pollution risk across the area.
The findings have just been published in GeoHealth journal.
The study, led by Dr Meryl Jagarnath of UCT’s Division of Environmental Health, integrated satellite-derived air quality data with a detailed social vulnerability index, offering a novel framework for advancing environmental justice in urban Africa.
Dr Jagarnath says the study, funded by the National Research Foundation, addresses a critical gap in air pollution science. “Conventional approaches to air quality assessment focus primarily on pollutant concentrations, often overlooking the social and structural conditions that shape exposure and health outcomes,” she says.
Using satellite observations from Sentinel-5P, the researchers constructed an air quality index capturing multiple pollutants including nitrogen dioxide (NO2), sulphur dioxide (SO2), ozone (O3), and particulate matter (PM).
The data was combined with a social vulnerability index derived from indicators of demographics, socioeconomic status, housing, infrastructure and land use. By integrating these datasets within a geographic information system, the research identified spatial “hotspots” where high levels of air pollution coincide with high levels of social vulnerability.
The findings showed that approximately 1,9-million people – or 40,3% of Cape Town’s population – live in areas classified as high- to very-high-risk.
“These areas are concentrated in informal settlements and historically disadvantaged neighbourhoods where residents face compounded challenges such as poor housing conditions, limited access to healthcare, and proximity to pollution sources,” says Dr Jagarnath.
According to Dr Jagarnath, Cape Town provides a critical case study for understanding the intersection of environmental and social risk. She says that as one of the most unequal cities in South Africa, Cape Town’s spatial patterns of segregation and deprivation continue to shape both exposure to environmental hazards and the capacity of communities to respond to them.
“The study highlights how these structural inequalities are reflected in the geography of air pollution risk, underscoring the need for approaches that explicitly incorporate environmental justice into air quality management,” she says.
The study was conducted in collaboration with Dr Lerato Shikwambana from the Earth Observation Directorate at the South African National Space Agency. This collaboration brought together expertise in environmental health and satellite-based atmospheric science, enabling the integration of Earth observation data into the assessment of air pollution risk in Cape Town.
“The application of Earth observation represents an important advancement in public and environmental health research,” says Dr Jagarnath, adding that satellite platforms provide continuous, large-scale and high-resolution data on atmospheric pollutants, overcoming the limitations of sparse and unevenly distributed ground-based monitoring networks.
In this study, she says, satellite-derived data provided comprehensive spatial coverage – including areas typically underrepresented in conventional air quality monitoring systems.
The findings have important implications for policy and practice, notes Dr Jagarnath.
“Current air quality management strategies often adopt uniform approaches that do not account for localised differences in exposure and vulnerability,” she says. “The spatially resolved risk maps produced in this study provide a basis for targeted, location-specific interventions enabling policymakers, urban planners, and public health practitioners to prioritise communities at greatest risk.
“Such interventions may include reducing emissions in high-risk areas, improving housing and infrastructure, increasing access to healthcare, and enhancing urban green spaces. By addressing both environmental exposures and underlying social conditions, these strategies have the potential to reduce health inequalities and improve overall population health.”
The study also highlights the value of integrating environmental data into health systems.
Dr Jagarnath says that spatial information on air pollution and vulnerability can support more informed clinical and public health decision-making – particularly for conditions associated with air pollution exposure, including respiratory and cardiovascular diseases.
“More broadly, the study demonstrates the potential of interdisciplinary approaches that combine environmental science, geospatial analysis, and public health,” Dr Jagarnath says. “As cities across Africa continue to grow, the integration of Earth observation into environmental health research offers a scalable and transferable model for assessing and managing urban environmental risks.
“By making visible the spatial distribution of air pollution risk and its intersection with social vulnerability, this study provides critical evidence base for advancing environmental justice in South Africa,” she adds.