Government responds to ‘rotten egg’ smell in Gauteng

The department of forestry, fisheries and the environment is probing reports of a strong sulphurous odour detected across parts of Gauteng, particularly in Johannesburg and Ekurhuleni and believes the “rotten egg” smell is probably caused by hydrogen sulphide. In a statement issued on Thursday, the department said it had received reports of the stench on 10 March and was analysing air quality data from the South African Air Quality Information System. Monitoring information showed that whilesulphur dioxidelevels were elevated, they remained within South Africa’s National Ambient Air Quality Standards.

However,hydrogen sulphidereadings recorded noticeable peaks at several monitoring stations, among them Secunda, Springs, Irene in Pretoria, Midstream and Buccleuch in Johannesburg. Although South Africa does not yet have national ambient air quality standards forhydrogen sulphide, the department said the concentrations detected were significantly higher than the World Health Organisation’s recommended nuisance odour threshold of 5.02 parts per billion. The department said prevailing south-easterly winds probably carried polluted air from Mpumalanga into Gauteng, affecting communities across Ekurhuleni, Johannesburg and Pretoria.

This is not the first time residents have experienced such an episode. Similar sulphurous odours were reported across Gauteng and Mpumalanga inFebruary 2022. After that incident, the department said it had worked with air quality authorities from Mpumalanga, North West and Gauteng to investigate the source of the pollution.

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Particular attention was given toSasol’s Secunda operations, which is one of the region’s largest industrial facilities and a significant contributor to sulphur dioxide and hydrogen sulphide emissions. While the investigation found that Sasol was operating within the legally permitted emission limits, authorities concluded that the existing limits might not adequately protect public health, particularly for communities living near major industrial sites. As a result, the department said the government had begun tightening emission standards for hydrogen sulphide produced during coal gasification processes. In August last year, the minister of forestry, fisheries and the environment published a notice proposing that the allowable emission limit for hydrogen sulphide be reduced from 3 500mg/m³ to 600mg/m³.

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