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Air in Senqu

Air in 2025 (modelled): nitrogen dioxide near the ground averaged 18 µg/m³, 1.8 times WHO’s guideline of 10; winters 23 µg/m³, summers 12 µg/m³.

Nitrogen dioxide (NO2) comes mostly from burning: power stations, vehicles, industry. Near the ground is what people breathe. The column is all of it in the air above, from the ground to the top of the sky, which is what a satellite sees. Sulphur dioxide (SO2) comes mostly from burning coal. Ozone forms in sunlight from other pollutants.

Modelled, not measured: these figures come from the Copernicus Atmosphere Monitoring Service’s reanalysis, a weather and chemistry model that takes in satellite readings. Its cells are about 80 km across, so a busy road or a smoky winter evening in one suburb is smoothed into the region around it. It is not a reading at any address.

2025

WHO’s 2021 guideline for nitrogen dioxide is 10 µg/m³ as a yearly mean. It is a long-term health guideline, not a legal limit (South Africa’s national standard for the yearly mean is set separately), and these are modelled regional means, not readings where you live.

Month by month

MonthNO2 near the groundOzone near the groundNO2 columnSO2 column
December 202512 µg/m³52 µg/m³60 µmol/m²84 µmol/m²
November 202512 µg/m³50 µg/m³72 µmol/m²83 µmol/m²
October 202516 µg/m³54 µg/m³91 µmol/m²108 µmol/m²
September 202520 µg/m³49 µg/m³99 µmol/m²115 µmol/m²
August 202524 µg/m³41 µg/m³106 µmol/m²121 µmol/m²
July 202524 µg/m³33 µg/m³116 µmol/m²128 µmol/m²
June 202524 µg/m³30 µg/m³118 µmol/m²106 µmol/m²
May 202522 µg/m³30 µg/m³112 µmol/m²106 µmol/m²
April 202518 µg/m³29 µg/m³102 µmol/m²92 µmol/m²
March 202518 µg/m³39 µg/m³82 µmol/m²91 µmol/m²
February 202513 µg/m³45 µg/m³72 µmol/m²85 µmol/m²
January 202511 µg/m³51 µg/m³68 µmol/m²100 µmol/m²
December 202411 µg/m³51 µg/m³66 µmol/m²97 µmol/m²
November 202412 µg/m³52 µg/m³67 µmol/m²87 µmol/m²
October 202417 µg/m³57 µg/m³82 µmol/m²109 µmol/m²
September 202419 µg/m³52 µg/m³93 µmol/m²108 µmol/m²
August 202421 µg/m³47 µg/m³101 µmol/m²110 µmol/m²
July 202422 µg/m³33 µg/m³110 µmol/m²113 µmol/m²
June 202422 µg/m³29 µg/m³117 µmol/m²133 µmol/m²
May 202424 µg/m³33 µg/m³115 µmol/m²119 µmol/m²
April 202417 µg/m³32 µg/m³91 µmol/m²100 µmol/m²
March 202416 µg/m³41 µg/m³78 µmol/m²105 µmol/m²
February 202413 µg/m³45 µg/m³69 µmol/m²104 µmol/m²
January 202412 µg/m³43 µg/m³56 µmol/m²79 µmol/m²

Over the last five years the NO2 column averaged 114 µmol/m² in winter against 66 µmol/m² in summer, and the SO2 column 121 µmol/m² against 87 µmol/m²: still winter air holds what is burnt close to the ground, and more is burnt to keep warm.

Every year since 2003

2003: 16 µg/m³2004: 15 µg/m³2005: 15 µg/m³2006: 16 µg/m³2007: 15 µg/m³2008: 15 µg/m³2009: 15 µg/m³2010: 16 µg/m³2011: 16 µg/m³2012: 16 µg/m³2013: 14 µg/m³2014: 16 µg/m³2015: 15 µg/m³2016: 16 µg/m³2017: 16 µg/m³2018: 16 µg/m³2019: 17 µg/m³2020: 17 µg/m³2021: 17 µg/m³2022: 18 µg/m³2023: 17 µg/m³2024: 17 µg/m³2025: 18 µg/m³200320082013201820232025
Nitrogen dioxide near the ground, each year’s mean (modelled). The line is WHO’s yearly guideline, 10 µg/m³.
Show the numbers
Nitrogen dioxide near the ground, the mean of each year, 2003 to 2025: every figure
When or whatFigure
200316 µg/m³
200415 µg/m³
200515 µg/m³
200616 µg/m³
200715 µg/m³
200815 µg/m³
200915 µg/m³
201016 µg/m³
201116 µg/m³
201216 µg/m³
201314 µg/m³
201416 µg/m³
201515 µg/m³
201616 µg/m³
201716 µg/m³
201816 µg/m³
201917 µg/m³
202017 µg/m³
202117 µg/m³
202218 µg/m³
202317 µg/m³
202417 µg/m³
202518 µg/m³

See it in the Copernicus Browser, the European Space Agency’s free viewer, on the newest image: Sentinel-5P, nitrogen dioxide · Sentinel-5P, sulphur dioxide. These are Sentinel-5P’s observed columns for one day, not our modelled yearly figures; days with cloud have gaps.

Every municipality, ranked · Everything we hold for Senqu · On the explore map

Source

Modelled, not measured: these figures come from the Copernicus Atmosphere Monitoring Service’s reanalysis, a weather and chemistry model that takes in satellite readings. Its cells are about 80 km across, so a busy road or a smoky winter evening in one suburb is smoothed into the region around it. It is not a reading at any address.

How we worked this out

What we changed: we averaged the reanalysis’s monthly means over each place by its area in each 0.75 degree cell, turned NO2 and ozone on the model’s lowest level from mass mixing ratio into micrograms per m3 with the month’s air density (surface pressure and temperature), and the columns from kg per m2 into micromol per m2.

Particles (PM2.5, PM10) and sulphur dioxide near the ground are not shown yet: the model reads them far higher over Gauteng and the Highveld than is plausible for a regional mean, so they wait for a check against ground stations.

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. Copernicus Atmosphere Monitoring Service (2020): CAMS global reanalysis (EAC4) monthly averaged fields. Copernicus Atmosphere Monitoring Service (CAMS) Atmosphere Data Store, DOI 10.24381/fd75fff2. Inness, A. and others (2019): The CAMS reanalysis of atmospheric composition, Atmos. Chem. Phys., 19, 3515 to 3556. Under CC BY 4.0.

Dataset: air quality by municipality, release of 12 November 2026.

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