Smelly skies over Joburg: What to know when the ‘rotten egg’ smell returns

Smelly skies over Joburg: What to know when the ‘rotten egg’ smell returns

If you’ve been wandering the streets of Johannesburg over the past weekend, you may have noticed it: that unmistakable “rotten egg” smell hanging over parts of the city. The stench isn’t new in fact, Johannesburg sees a recurring pattern of sulphur odours during the first quarter of the year but it always prompts questions and concerns from residents.

The city has confirmed that this weekend’s smell likely originated from industrial operations in neighbouring Mpumalanga. Though the source is still being traced, authorities emphasise that long-range air movement carries hydrogen sulphide (H₂S) the gas responsible for the foul odour across provincial boundaries.

Why the city smells like sulphur

Johannesburg itself has few heavy industrial operations. The city relies on six ambient air quality monitoring stations and two dedicated hydrogen sulphide sensors in Buccleuch and Alexandra to track pollutants such as sulphur dioxide, nitrogen oxides, ozone, and particulate matter.

H₂S is particularly concerning because it’s detectable even at very low concentrations, and its characteristic smell rotten eggs can travel hundreds of kilometres. The municipality notes that the recent odour was “widespread and not confined to a single location,” pointing to industrial activities east of Gauteng, including power generation and petrochemical plants.

Sasol, which operates one of the largest plants in Secunda, said all its systems were functioning normally and emissions remained within licence limits. “Recent assessments, including independent monitoring, do not indicate exceedances of ambient air quality standards,” the company said.

Health risks and precautions

While a passing whiff is mostly unpleasant, prolonged exposure can pose health risks. The city advises residents, particularly children and the elderly, to remain indoors if the smell is strong and avoid strenuous outdoor activity. Symptoms from H₂S exposure may include:

• Eye and throat irritation

• Headaches and dizziness

• Fatigue

Longer or repeated exposure can lead to respiratory problems and, in rare cases, neurological effects.

Social media buzz

As always, the stench didn’t go unnoticed online. Residents shared memes about “Joburg smelling like a rotten factory” and speculated on the culprit, while others urged neighbours to check on vulnerable family members. Experts stressed that while social media amplifies concern, official channels such as the Johannesburg Environment, Infrastructure and Services Department remain the best source for guidance.

A recurring phenomenon

According to city records, these sulphur odours tend to appear between January and March, influenced by both industrial activity and seasonal wind patterns that carry pollutants across provinces. While unpleasant, the phenomenon is closely monitored, and local authorities continue to track hydrogen sulphide levels to protect residents’ health.

For now, the advice is simple: stay informed, limit outdoor exposure when the smell is strong, and trust that the city’s monitoring systems are keeping an eye on the invisible gas drifting over Joburg’s skyline.