How clean is your air? Nitrogen dioxide in every municipality, and its sources from space

The air over parts of Gauteng and Mpumalanga carries up to 4.1 times the nitrogen dioxide the World Health Organization advises. That is a model’s estimate for 2025, not a reading on any street. But it is the same model for the whole country, so it lets you compare your municipality with every other one.

• 70 of 213Municipalities above the World Health Organization’s yearly guideline
• 4.1 timesThe guideline in Govan Mbeki, around Secunda, the highest
• 213 of 213Municipalities with more in winter than in summer

What we measured, and how

Nitrogen dioxide is a gas released when fuel burns, mostly in traffic and in industry. The World Health Organization’s guideline is a yearly average of no more than 10 micrograms in each cubic metre of air (written 10 µg/m³).

South Africa has too few public ground stations to cover every town. So these figures come from a model: the Copernicus Atmosphere Monitoring Service, run for the European Union, combines satellite readings with weather data to estimate the air over the whole planet. Its blocks are about 80 km wide. We averaged them over each municipality, district and province, month by month, back to 2003.

That means every number here is a regional average. A busy road, or a smoky winter evening in one suburb, is smoothed into the region around it. It is not a reading at your address.

Where it is highest

In 2025, 70 of the 213 municipalities were above the guideline, and 28 were above twice the guideline.

The ten highest are all in Gauteng and Mpumalanga:

The lowest are on the north-west edge of the Northern Cape: Khâi-Ma and Richtersveld, both at 1.3.

Province by province

Three provinces are above the guideline. North West, KwaZulu-Natal and Limpopo sit just under it. A province’s figure is the average over all its land, so a clean countryside pulls a province down even where its towns are higher.

The eight big cities

Six of the eight are above the guideline. Cape Town is just over the line. Only Nelson Mandela Bay and Buffalo City are under it.

Why the Highveld

In November 2007 the government declared the Highveld a national air pollution hotspot: the Highveld Priority Area, which covers Ekurhuleni and parts of Gauteng and Mpumalanga, including Govan Mbeki, Emalahleni, Lekwa and Victor Khanye. The Minister’s statement listed the sources: power stations, petrochemical plants, metal smelters, coal mines, and households that still burn coal.

The government’s own air quality plan for the area, published in 2011, counted where the pollution comes from:

The plan counted 11 Eskom coal power stations in the area, among them Kendal, Matla, Kriel and Duvha, and says the petrochemical figure is “dominated by Sasol’s Secunda operations”. These shares are from 2011, built on data from 2004 to 2006; a second plan was gazetted in March 2025.

Our data points the same way. Sulphur dioxide is a gas that comes from burning coal and oil and from smelting. The five municipalities with the most sulphur dioxide in the air above them in 2025 are all on the Mpumalanga Highveld, inside that priority area: Govan Mbeki, Emalahleni, Lekwa, Victor Khanye and Dr Pixley Ka Isaka Seme. (This is the amount in the whole column of air overhead, which is what a satellite sees. It is not what people breathe at ground level.)

The sources, seen from space

These are real pictures from the European Union’s Sentinel-2 satellites, taken at about a quarter past ten on clear winter mornings in 2025. Each shows an area 16 km wide. Nothing has been retouched.

A word of care about what the pictures show. The white plumes are steam and smoke, and the dark streaks beside them are their shadows. Nitrogen dioxide and sulphur dioxide themselves are invisible in a picture like this. So a plume tells you a plant was running that morning, and nothing about how much it emitted. The shares above come from the government’s count, not from the pictures. We chose mornings when the sky was clear and the plumes showed well.

Worse in winter

In all 213 municipalities, the model’s nitrogen dioxide was higher in winter (June to August 2025) than in summer (January, February and December 2025). In Johannesburg, winter ran at 1.6 times summer’s level. In Buffalo City, 3.4 times.

Prof Rebecca Garland of the University of Pretoria has explained why Highveld winters are worse: there is very little rain and the weather is calmer, which can trap pollution close to the ground, and people burn more wood and coal for cooking and heating.

Our place pages show winters and summers averaged over the last five years, so their figures can differ a little from these, which are for 2025 alone.

What it means for your health

Nitrogen dioxide irritates the airways. The United States Environmental Protection Agency says that breathing air with a lot of it, even for a short time, can make breathing diseases worse, asthma above all, and bring on coughing, wheezing or difficulty breathing. Over longer periods it may contribute to people developing asthma. People with asthma, children and older people are most at risk.

Three things that follow from the sources:

• Winter is the worst time, as the section above shows.
• Smoke indoors adds to it. The World Health Organization says that open fires and simple stoves burning coal, wood or paraffin pollute the air inside a home, and that women and children carry most of the harm. It recommends cleaner fuels and better ventilation. In plain words: where you can, let fresh air in.
• Look at real readings where there are stations. The government’s South African Air Quality Information System (saaqis.environment.gov.za) makes its air quality data available to the public, with hourly monitoring data by station.

This is not medical advice, and our figures cannot tell you what you are breathing at your address.

How sure are we?

We checked the model against the City of Cape Town’s own monitoring stations, the one set of ground readings we may lawfully use so far. Over 138 months between 2013 and 2024, the stations averaged 12.3 µg/m³ and the model 10.1: the model read 82% of what the stations measured. That is close on average. Month by month the two only loosely agree (a correlation of 0.31), so do not read much into one month in one place.

Three more things to know:

• The law. South Africa’s own limit for nitrogen dioxide is a yearly average of 40 µg/m³, four times the World Health Organization’s guideline. Three of our municipal figures sit just above 40. That does not show any place breaking the limit: the limit is tested at a monitoring station, and ours are modelled averages over a whole region.
• No trend. We do not say whether the air is getting better or worse. The model’s figures rise steadily from 2003 to 2025 almost everywhere, with no dip in 2020 when the country locked down. That suggests the model is following its own estimates of emissions rather than what happened, so we leave the trend out.
• No particles yet. Fine particles (the dust and smoke that do the most harm to lungs) are not in our data. The model reads them implausibly high over Gauteng and the Highveld, so we are holding them back until ground stations can check them.

Check yours

Look up your own municipality, month by month since 2003: unmapped.co.za/air. Every page says what the figure is, how it compares with the guideline, and that it is modelled. Govan Mbeki’s, for example: unmapped.co.za/air/govan-mbeki.

Sources and credits

• Our air quality dataset, release 2026-11-12 (6,302 records): nitrogen dioxide and ozone near the ground, and the nitrogen dioxide and sulphur dioxide columns, monthly from 2003 to 2025, for every 2026 municipality, district and province. About the dataset.
• Modelled by the Copernicus Atmosphere Monitoring Service: CAMS global reanalysis (EAC4) monthly averaged fields, cells about 80 km, averaged over each place by area. Licence CC BY 4.0, doi.org/10.24381/fd75fff2. Contains modified Copernicus Atmosphere Monitoring Service information 2003 to 2025. Neither the European Commission nor ECMWF is responsible for any use that may be made of the Copernicus information or data it contains.
• The guideline: World Health Organization, WHO global air quality guidelines, 2021. Where the gases come from: WHO, Ambient (outdoor) air pollution, fact sheet, 24 October 2024.
• The Highveld Priority Area: statement by the Minister of Environmental Affairs and Tourism, 26 November 2007.
• Where the Highveld’s pollution comes from: Department of Environmental Affairs, Highveld Priority Area Air Quality Management Plan, 2011, executive summary and Table E1.
• The satellite pictures: Copernicus Sentinel-2 L2A true colour, 10 m, scenes S2C_35JQL_20250729_0_L2A (Secunda), S2B_35JPM_20250704_0_L2A (Kendal) and S2C_35JQL_20250818_0_L2A (Kriel and Matla), from the open copy on Amazon Web Services. Contains modified Copernicus Sentinel data 2025.
• Health: United States Environmental Protection Agency, “Basic Information about NO2”. World Health Organization, “Household air pollution”, fact sheet, 16 December 2025.
• Winter: Prof Rebecca Garland, University of Pretoria, “The air in South African Highveld cities smells foul in the winter. Here’s why”, The Conversation, 19 June 2022 (republished by TechCentral).
• The legal limit: National Ambient Air Quality Standards, Government Notice 1210, Government Gazette 32816, 24 December 2009.
• The ground check: City of Cape Town air quality monitoring stations, hourly readings, Open Data Portal.
• Station data: South African Air Quality Information System (SAAQIS), from its own home page (“It makes data available to stakeholders including the public”; custodian: the South African Weather Service), read 13 November 2026. We link to it; we don’t use its data.
• The map: municipal boundaries from the Municipal Demarcation Board (2026). Rivers on the film’s maps: Natural Earth.

Made by Unmapped Dataworks. The film’s voice is AI-generated.