Levy Masiteng
The sulphur-like smell that unsettled residents across large parts of Johannesburg last week was not caused by a local source, but was most likely blown into the city from industrial areas in Mpumalanga, the City of Johannesburg has said.
The explanation followed numerous social media complaints received by the city, with residents in areas like Sandton, Randburg, Roodepoort, Fourways and Parktown reporting a strong, pungent smell reminiscent of “rotten eggs”.
“The odour described by residents as a ‘rotten egg’ smell is more commonly associated with hydrogen sulphide (H₂S),” said the city’s Environment & Infrastructure Services Department (EISD) late on Monday.
According to the department, investigations suggested that the odour was the result of “transboundary” air pollution linked to industrial activity in the Highveld Priority Area, which hosts power generation and petrochemical operations.
“Given the geographical spread of the complaints and prevailing meteorological conditions, it is likely that the City was impacted by a transboundary pollution source.”
The city said the complaints were formally brought to the department’s attention on 16 January.
In response, EISD officials conducted field surveys across the affected areas and confirmed that the odour was widespread and not confined to a single location, “thereby ruling out a localised source within the city”.
The city said current weather patterns were conducive to the long-range transport of air pollutants from the Highveld Priority Area and industrial complexes in Mpumalanga, which include power generation and petrochemical operations.
The characteristics of the reported odour were consistent with emissions typically associated with such activities, according to the city.
It added that Johannesburg does not host major heavy industrial activities, and that all listed industrial operations within the city are licensed and routinely monitored by the Environmental Management Inspectorate to ensure compliance with environmental legislation.
As a precautionary measure, the city said communities are advised to remain indoors during periods of strong sulphur-like odours and avoid strenuous outdoor activities.
“Vulnerable groups, including the elderly and children, should be closely monitored for symptoms such as eye and throat irritation, headaches, dizziness, and fatigue. Prolonged exposure may result in more serious health effects, including respiratory complications and potential neurological impacts.”
Johannesburg operates six ambient air quality monitoring stations that measure particulate matter, sulphur dioxide, oxides of nitrogen and ozone.
However, in light of recurring incidents, the city has also invested in hydrogen sulphide monitoring equipment, currently deployed at the Buccleuch and Alexandra monitoring stations to detect elevated H₂S levels.
Similar sulphur-related odour episodes have occurred intermittently over the past five years, particularly between January and March.
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