Africa's wealthiest city lies not far from the country's coal mines, and the rotten-egg smell of sulphur has often been present in the air.
The Minister of Forestry, Fisheries and the Environment, Willie Aucamp, attributed the stink afflicting Johannesburg to hydrogen sulphide emissions from mining and industrial operations as far as 400 km east.
"This (sulphurous smell) came from mines that exceeded their emissions," Aucamp told Reuters in an interview in Johannesburg.
"We don't know which specific mines yet. Investigations are still ongoing."
The app, launching later this year, uses data from hundreds of air-monitoring systems.
It sends out notifications and advises residents on protective measures, such as wearing a mask during pollution surges, although masks only help with smog and soot, not gases like sulfur compounds.
Coal employs tens of thousands of people, provides three-quarters of South Africa's electricity, and a quarter of its liquid fuels, which are converted from coal by Sasol.
Johannesburg resident Philasande Shange, who has asthma, said he developed a cough in February and March, which a health practitioner linked to the city's poor air quality.
"I couldn’t breathe or sleep, and I lost 15kg," Shange told Reuters in an interview in Braamfontein.
Reuters interviewed five residents who reported flu-like symptoms, dizziness, sinus inflammation and asthma flare-ups.
Bruce Mellado, a researcher who pioneered the app SACAQM (South African Consortium of Air Quality Monitoring), said their system had detected a growing frequency of pollution spikes.
South Africa's two biggest polluters, Sasol and state-owned utility Eskom, were granted extensions to emissions exemptions in 2025. Their largest facilities lie east of Johannesburg.
Sasol spokesperson Alex Anderson said in an emailed response to questions that "no operational incidents or abnormal process conditions have been identified that would indicate an uncontrolled or atypical release" of sulfur emissions.
Eskom did not respond to a request for comment.
Authorities point to the need to balance environmental and economic imperatives when justifying lax air quality enforcement. Activists say that it underestimates the economic cost of pollution-related disease.
"We need more community monitoring (to) ... understanding how much air pollution actually costs us," said Rico Euripidou, a campaign coordinator at GroundWork.
Reuters, the news and media division of Thomson Reuters, is the world's largest multimedia news provider, reaching billions of people worldwide every day.
Go to: https://www.reuters.com/
