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Air in Port St Johns
Air in 2025 (modelled): nitrogen dioxide near the ground averaged 5.5 µg/m³, under WHO’s guideline of 10; winters 9.1 µg/m³, summers 3.2 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
- 5.5 µg/m³Nitrogen dioxide near the groundThe year’s mean; 0.6 × WHO’s guideline
- 9.1 µg/m³In winterJune to August, against 3.2 µg/m³ in summer (last five years)
- 59 µmol/m²NO2 in the column aboveWhat a satellite sees, not what you breathe
- 53 µmol/m²SO2 in the column aboveMostly from burning coal
- 47 µg/m³Ozone near the groundThe year’s mean
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
| Month | NO2 near the ground | Ozone near the ground | NO2 column | SO2 column |
|---|---|---|---|---|
| December 2025 | 3.3 µg/m³ | 51 µg/m³ | 38 µmol/m² | 35 µmol/m² |
| November 2025 | 3.3 µg/m³ | 52 µg/m³ | 42 µmol/m² | 33 µmol/m² |
| October 2025 | 4.0 µg/m³ | 57 µg/m³ | 56 µmol/m² | 52 µmol/m² |
| September 2025 | 5.0 µg/m³ | 57 µg/m³ | 60 µmol/m² | 61 µmol/m² |
| August 2025 | 7.8 µg/m³ | 49 µg/m³ | 75 µmol/m² | 82 µmol/m² |
| July 2025 | 8.8 µg/m³ | 44 µg/m³ | 78 µmol/m² | 80 µmol/m² |
| June 2025 | 9.8 µg/m³ | 38 µg/m³ | 94 µmol/m² | 73 µmol/m² |
| May 2025 | 8.2 µg/m³ | 40 µg/m³ | 79 µmol/m² | 72 µmol/m² |
| April 2025 | 5.3 µg/m³ | 43 µg/m³ | 57 µmol/m² | 38 µmol/m² |
| March 2025 | 5.0 µg/m³ | 47 µg/m³ | 51 µmol/m² | 37 µmol/m² |
| February 2025 | 2.7 µg/m³ | 44 µg/m³ | 41 µmol/m² | 29 µmol/m² |
| January 2025 | 3.1 µg/m³ | 47 µg/m³ | 40 µmol/m² | 42 µmol/m² |
| December 2024 | 2.9 µg/m³ | 47 µg/m³ | 38 µmol/m² | 43 µmol/m² |
| November 2024 | 3.1 µg/m³ | 57 µg/m³ | 43 µmol/m² | 42 µmol/m² |
| October 2024 | 4.8 µg/m³ | 67 µg/m³ | 48 µmol/m² | 44 µmol/m² |
| September 2024 | 5.4 µg/m³ | 64 µg/m³ | 60 µmol/m² | 57 µmol/m² |
| August 2024 | 11 µg/m³ | 57 µg/m³ | 90 µmol/m² | 75 µmol/m² |
| July 2024 | 9.4 µg/m³ | 46 µg/m³ | 91 µmol/m² | 78 µmol/m² |
| June 2024 | 8.2 µg/m³ | 41 µg/m³ | 75 µmol/m² | 90 µmol/m² |
| May 2024 | 9.7 µg/m³ | 38 µg/m³ | 76 µmol/m² | 77 µmol/m² |
| April 2024 | 5.4 µg/m³ | 44 µg/m³ | 60 µmol/m² | 54 µmol/m² |
| March 2024 | 4.3 µg/m³ | 45 µg/m³ | 48 µmol/m² | 52 µmol/m² |
| February 2024 | 3.2 µg/m³ | 44 µg/m³ | 39 µmol/m² | 42 µmol/m² |
| January 2024 | 3.2 µg/m³ | 42 µg/m³ | 30 µmol/m² | 27 µmol/m² |
Over the last five years the NO2 column averaged 82 µmol/m² in winter against 40 µmol/m² in summer, and the SO2 column 79 µmol/m² against 36 µmol/m²: still winter air holds what is burnt close to the ground, and more is burnt to keep warm.
Every year since 2003
Show the numbers
| When or what | Figure |
|---|---|
| 2003 | 4.9 µg/m³ |
| 2004 | 4.5 µg/m³ |
| 2005 | 4.9 µg/m³ |
| 2006 | 4.7 µg/m³ |
| 2007 | 5.2 µg/m³ |
| 2008 | 4.6 µg/m³ |
| 2009 | 5.1 µg/m³ |
| 2010 | 5.2 µg/m³ |
| 2011 | 4.6 µg/m³ |
| 2012 | 4.9 µg/m³ |
| 2013 | 5.5 µg/m³ |
| 2014 | 5.5 µg/m³ |
| 2015 | 5.2 µg/m³ |
| 2016 | 5.1 µg/m³ |
| 2017 | 4.9 µg/m³ |
| 2018 | 5.3 µg/m³ |
| 2019 | 5.6 µg/m³ |
| 2020 | 5.4 µg/m³ |
| 2021 | 5.4 µg/m³ |
| 2022 | 5.6 µg/m³ |
| 2023 | 5.7 µg/m³ |
| 2024 | 5.9 µg/m³ |
| 2025 | 5.5 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 Port St Johns · 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.