Johannesburg residents are once again worried about the quality of the city’s air. A strong rotten-egg smell has spread across large parts of the metro, caused by elevated levels of hydrogen sulphide and sulphur dioxide.
The City of Johannesburg’s air quality monitoring confirmed that the foul odour experienced between 9 and 11 March was linked to spikes in the two industrial pollutants.
Experts say the pollution likely travelled from the Highveld industrial belt east of Gauteng, where large coal-burning facilities are concentrated.
Strong winds brought in pollution
Lauri Myllyvirta of the Centre for Research on Energy and Clean Air said wind patterns at the time point to emissions from facilities in Mpumalanga moving westwards and accumulating over Gauteng.
“The entire period of 9 to 11 March, when Johannesburg and surrounding areas experienced high pollution levels, wind from the east and conditions that caused pollution from Eskom coal power plants and the Sasol Secunda coal-to-liquids plant to build up in the city,” he said.
Sasol emits rotten-egg smell
He added that hydrogen sulphide is responsible for the rotten-egg smell, and most likely comes from the Sasol facility because it is the only major industrial source of the gas in the region.
The Highveld Priority Area east of Gauteng hosts most of Eskom’s coal-fired power stations alongside Sasol’s petrochemical complex.
Hydrogen sulphide, known for its distinctive odour, can irritate the eyes, nose and throat and may cause breathing difficulties, headaches and dizziness at low concentrations.
Industrial emissions pose health risks
Environmental accountability organisation Just Share said recurring pollution episodes highlight the health risks industrial emissions pose to the region.
Robyn Hugo, Just Share Director of Climate Change Engagement, said there is resistance to acknowledging the scale of industrial emissions linked to the smell.
“The fact that Sasol may be operating within the confines of its air emission licence does not mean that its emissions are at acceptable levels. Sasol is the biggest private emitter of toxic air pollutants in Africa and has already received a number of concessions from government in relation to air pollution,” she said.
“These concessions to industry delay and weaken air quality regulation despite stark evidence of severe human health impacts from industrial pollution.”
City is investigating air quality
City officials said they activated their air quality monitoring systems after receiving complaints from residents across parts of Johannesburg, including Sandton, Randburg, Roodepoort and Fourways. The sulphur-like odour was also noticed earlier this year on 16 January.
City Manager Dr Floyd Brink said the metro immediately launched an investigation through its Environment and Infrastructure Services Department.
“Protecting the health and wellbeing of residents remains our priority. Our technical teams are actively monitoring air quality data and working with other spheres of government to determine the source of the odour and ensure residents are kept informed,” Brink said.
Monitoring stations in Buccleuch and Alexandra detected elevated hydrogen sulphide levels during the episode.
According to Dr Tebogo Modiba, Executive Director of the department, concentrations of hydrogen sulphide peaked at about 36 to 37 parts per billion in Alexandra, while sulphur dioxide reached around 52 parts per billion.
‘Generally low concentrations’
Although the spikes were enough to produce a noticeable smell, officials said the concentrations remained generally low and close to background levels. The city added that Johannesburg itself does not host major heavy industrial operations, confirming that the characteristics of the odour are consistent with emissions typically associated with the Highveld industrial complex east of the metro.
Authorities said the matter has been escalated to the national Department of Forestry, Fisheries and the Environment and the Gauteng provincial government to investigate possible cross-boundary pollution sources while further air quality monitoring continues.
