Dying to breathe: Many of the priority areas exceeded South Africa’s national ambient air quality standards,
often in regions with high concentrations of vulnerable people. Photo: Delwyn Verasamy
Air pollution is contributing to higher rates of respiratory disease and tuberculosis (TB) in South Africa’s three declared air pollution priority areas, with children, youth and older adults facing the greatest risks, a new epidemiological study has revealed.
Scientists from the South African Medical Research Councili on Tuesday presented the findings of their multi-site study conducted across the Highveld Priority Area (HPA), the Vaal Triangle Priority Area (VTPA) and the Waterberg–Bojanala Priority Areaa (WBPA).
The research, funded by theClean Air Fund, examined the association between ambient (outdoor) air pollution and mortality and morbidity across the country’s most industrialised regions.
The HPA includes Sedibeng and Gert Sibande, the VTPA covers Nkangala and Fezile Dabi and the WBPA comprises the Waterberg and Bojanala districts.
The regions host coal-fired power stations, smelters, petrochemical plants and refineries alongside urban and peri-urban communities. They were all designated based on elevated pollutant concentrations and significant population exposure.
Presenting the findings, professor Caradee Wright, the chief specialist scientist at the MRC’s environment and health research unit, said pollution levels in many of the priority areas exceeded South Africa’s national ambient air quality standards, often in regions with high concentrations of vulnerable people.
The key pollutants of concern include PM2.5 (fine inhalable particles with diameters generally 2.5 micrometers and smaller), which are strongly associated with mortality and respiratory disease and nitrogen dioxide, linked to pneumonia and respiratory deaths. Sulphur dioxide and ozone showed highly seasonal and district-specific effects, with the greatest impacts observed in winter.
“The challenge here is that these areas have many vulnerable groups — children with pre-existing conditions like asthma, older adults with chronic illnesses, pregnant women and other populations in densely populated communities,” Wright said.
“Children breathe differently to adults, so they experience air pollution in a different way. Older adults’ organs are under stress, so pollution adds an additional burden.”
She highlighted a key finding typical of how air pollution affects health: for every 10 micrograms per cubic metre increase in PM2.5, the mortality risk rose by 14% to 19%.
“That is quite a lot,” Wright said. “That’s essentially between one in four, one in five people, being affected by exposure to particulate matter and having it associated with a death outcome.
“There were stronger links with TB and pneumonia in relation to air pollution. Winter months are definitely the time where we see the highest burden,” she said.
“This does imply that there must be other sources besides, for example, the typical industrial sources, which run all the time and one would surmise that it could be domestic solid fuel burning, which people would be doing for heating in their homes.”
Until now, there has been no comprehensive assessment of long-term trends in air pollution in relation to mortality and morbidity in the three air pollution priority areas. The scientists applied a retrospective longitudinal methodology, supplemented by a case-crossover analysis as a sensitivity test, with results stratified by season.
The health effects included the all-cause mortality datasets from Statistics South Africa and morbidity data from the department of health information system.
The morbidity data included pneumonia under five and new cases of TB-related hospital admissions. The health department provided the morbidity data and Stats SA the morbidity datasets. The timeframe was from 1997 to 2023.
While meteorological data were not consistently available, “triangulation across multiple models and regions produced robust findings”, the study added.
In the HPA, the study recorded the highest concentrations of PM2.5 and nitrogen dioxide, particularly in winter, closely linked to increased respiratory mortality.
In the VTPA, strong associations were observed between PM2.5 exposure and TB-related deaths, alongside significant impacts from sulphur dioxide emissions from industrial activity.
In the WBPA, elevated health risks were associated with sulphur dioxide and ozone, reflecting coal-fired power generation and smelting operations. Despite a lower population density, communities in these areas remain at significant risk.
District-level analysis found statistically significant associations between PM10 and sulphur dioxide exposure and increased mortality. Nkangala exhibited the highest
risks, particularly in spring and autumn, probably influenced by seasonal heating practices, regional meteorology and pollutant accumulation.
Fezile Dabi showed a persistent health burden during colder months, while Sedibeng displayed consistently elevated risks in winter and spring due to high baseline exposure and dense populations.
Gert Sibande “showed moderate but impactful pollution events” and Waterberg and Bojanala, though less populated, “still exhibited noteworthy associations”.
The researchers said the findings highlighted the short lag between exposure and mortality, suggesting that acute interventions — such as real-time air quality alerts, emergency healthcare readiness and targeted emissions control during high-risk seasons — could substantially reduce health impacts.
Sustained structural measures were also required in districts with multi-season risks, including stricter enforcement of air quality regulations, monitoring of industrial emissions and urban planning to reduce exposure.
Globally, air pollution is recognised as a leading environmental threat to health. The World Health Organisation estimates that nearly 800 000 premature deaths occur in Africa each year because of poor air quality.
Dr Chantelle Howlett-Downing, a senior scientist at the MRC’s environment and health research unit, said TB remained a major cause of death across the priority areas, with strong seasonal patterns.
The highest TB mortality counts were recorded in Ekurhuleni and Johannesburg, peaking in winter and spring, with more than 7 000 deaths per season reported in Ekurhuleni alone.
The seasonal spikes, she said, were probably driven by winter crowding and poor ventilation, which increased transmission risk. Statistical analysis showed strong correlations in TB mortality across seasons.
Respiratory disease was the single largest mortality burden. Johannesburg recorded more than 29 000 respiratory deaths across all age groups over the study period, with Nkangala and Gert Sibande also showing high numbers.
Winter peaks were pronounced, with Johannesburg experiencing more than 5 800 respiratory deaths in winter alone.
Children and young people bore a disproportionate share of the burden, representing about 42% of respiratory deaths in Nkangala.
Cardiovascular disease also contributed significantly to mortality, with the highest numbers recorded in Johannesburg, Sedibeng and Nkangala. Cardiovascular deaths were more evenly distributed across seasons, although slight winter increases were noted, with older adults accounting for more than 70% of cases.
Morbidity data reinforced the patterns. Hospital admissions for pneumonia in children under five and TB showed strong winter peaks.
A pseudo case-crossover analysis confirmed consistent associations between air pollution and health outcomes, though effect sizes were smaller than those observed in mortality analyses.
For example, PM10 exposure was linked to TB-related pneumonia admissions in the VTPA, while nitrogen dioxide exposure correlated with respiratory hospital visits in the HPA.
The research was conducted as part of a broader Clean Air Fund initiative, which aims to reduce air pollution in South Africa through integrated policy pathways linking air pollution, climate change, health and the economic costs of pollution-related disease.
Vumile Senene, the country lead for the Clean Air Fund in South Africa, said that because the three priority areas suffered the worst air quality in the country, “we wanted to get a better understanding of what people experience in these areas.
“Through other reports that the Clean Air Fund publishes … it is estimated that over 8 million people annually die as a result of air pollution … We hope that through this report, we lay the foundation for the regional work to be done but also we want to input into policies and plans that are currently under way.”
From a policy perspective, Wright emphasised the urgency of action.
“We do need stricter enforcement of our air quality standards,” she added. “It takes investment, commitment and stakeholder buy-in, but if we want to see change, we have to meet those standards. We also need to integrate air quality data into health and energy policy.”
Air pollution remains a significant but preventable health risk. “Coordinated action across environmental, health and energy sectors is urgently needed to reduce premature deaths and protect vulnerable communities.”