The Sasol Secunda synthetic fuel plant in the town of Secunda.
Leon Sadiki/Bloomberg via Getty Images
- Residents in Johannesburg, Ekurhuleni and Pretoria have reported a strong sulphurous odour.
- The smell is likely caused by elevated hydrogen sulphide levels transported from Mpumalanga due to prevailing winds.
- The government says it is tightening emission standards and introducing hydrogen sulphide as a regulated pollutant to better protect public health and prevent future odour episodes.
Since Tuesday, residents across Gauteng – Johannesburg, Ekurhuleni and Pretoria – have been contending with a pungent sulphurous odour.
The Department of Forestry, Fisheries and the Environment attributes the stench to high hydrogen sulphide levels carried from Mpumalanga by dominant south-easterly winds.
Despite the sulphurous odour, the department reported that air quality monitoring data from the South African Air Quality Information System indicated sulphur dioxide levels, while elevated, still complied with National Ambient Air Quality Standards during this period.
However, hydrogen sulphide monitoring data showed sharp peaks at the Secunda, Springs, Irene (Pretoria), Midstream and Buccleuch air quality stations.
“Although there are currently no national ambient air quality standards for hydrogen sulphide, these pollution levels were significantly higher than the World Health Organisation’s recommended threshold for ambient nuisance odour, which is 5.02 parts per billion,” explained the minister’s spokesperson, Zolile Nqayi.
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“Based on these observations, it is highly likely that the complaints raised by the public were prompted by elevated levels of hydrogen sulphide.”
Nqayi further stated that meteorological data confirmed that dominant south-easterly winds facilitated the transport of pollutants from Mpumalanga into Gauteng, impacting Ekurhuleni, Johannesburg and Pretoria.
This type of event has occurred before.
In March 2025, News24 reported on an episode that left Johannesburg smelling like rotten eggs.
In February 2022, residents in Mpumalanga and Gauteng experienced similar sulphurous incidents.
At the time, the department conducted investigations in collaboration with air quality authorities from Mpumalanga, the North West and Gauteng.
Nqayi said Sasol Secunda Operations was identified as a significant contributor to sulphur dioxide and hydrogen sulphide emissions.
A multi-stakeholder task team was subsequently established to investigate complaints and develop a proactive, long-term plan to improve the management of sulphur dioxide and hydrogen sulphide emissions, beyond responses triggered by public complaints.
He added that investigators determined that while Sasol Secunda Operations complied with legal emission limits, these limits failed to sufficiently protect public health, especially for communities surrounding Secunda.
Under certain weather conditions, these emissions can drift from Mpumalanga into Gauteng, triggering the odour episodes now affecting the public.
Legislative improvements
Following the 2022 incident, Nqayi said two key legislative improvements had been identified and were currently being implemented.
He said the government is tightening hydrogen sulphide emission standards for coal gasification to drastically cut releases.
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“The department is also in the process of introducing hydrogen sulphide as a criteria pollutant under the National Environmental Management: Air Quality Act.
“This will allow South Africa to establish national ambient air quality standards for hydrogen sulphide, aligned with international health protection guidelines.”
Consultations with provinces and municipalities on these standards continue, with amendments expected to be completed this year.
Health effects of hydrogen sulphide
Exposure to hydrogen sulphide may cause irritation to the eyes and respiratory system. Other possible health effects include dizziness, headaches, nausea, stomach upset, weakness, irritability and breathing difficulties.
In severe cases, high exposure may lead to convulsions, loss of consciousness or respiratory complications.
Nqayi said:
Children may be particularly vulnerable because they breathe more rapidly relative to their body size and may therefore receive higher exposure levels than adults in the same environment.
“The department therefore urges members of the public in affected areas to report persistent strong odours to local environmental health authorities or health authorities.”
The department reassured the public that it would continue to monitor the situation closely and work with provincial and municipal authorities to identify the sources of emissions and ensure compliance.
Noxolo Sibiya
www.news24.com
