Task team investigates cause of stench over Gauteng and North West in June

A task team investigating complaints about the sulphurous smell over parts of Gauteng and the North West in June has determined that a combination of weather events and emissions from industry were probably responsible.

The task team comprises environmental and air quality officials from the department of forestry, fisheries and the environment and the provincial departments in Mpumalanga, Gauteng, the North West and the Free State.

The team’s interim internal report, handed to minister Barbara Creecy, reflects that the sulphur smell may have emanated from industry operations in Mpumalanga and as a result of unusual air circulation patterns that resulted in the smell being blown over Gauteng and parts of the North West during the week of June 5-12.

The interim investigations show that a low-pressure system in the north of the Mozambique channel caused a relatively unusual circulation pattern over the region during the days on which the public raised complaints about the stench.

These conditions may have created prevailing south-easterly winds that transported air pollution from Mpumalanga into Gauteng and the North West, particularly over Ekurhuleni, Johannesburg and Pretoria.

Ambient air quality monitoring observations reflected on the SA Air Quality Information System (SAAQIS) show that despite industry complying with air quality standards in Gauteng and Mpumalanga, ambient levels of sulphur dioxide were higher than usual during the period.

But no emergency incident (upset conditions, start-ups or shutdowns) were reported by any facilities in Mpumalanga, the North West, Gauteng and the Free State with the potential to release large quantities of sulphur dioxide and/or hydrogen sulphide in the week, the department said.

“Some of the public complaints about the sulphurous odour coincided with incidents when sulphur dioxide was higher than usual during the period in question. However, the elevated readings were unlikely to have caused any health effects on the surrounding communities.”

The task team will investigate and recommend possible policy interventions to further reduce hydrogen sulphide pollution and address concerns about public safety and the possible long-term health effects of exposure to improve the management of sulphur dioxide and hydrogen sulphide emission sources beyond the responses triggered by public complaints, the department said.

“The investigation will include engaging with industries from identified areas where hydrogen sulphide is of concern, to discuss short-term and long-term management of sulphurous odorants.”

Nationally, there are four areas where actual or potential large-scale hydrogen sulphide emission sources are located: Secunda; Sasolburg/Sedibeng; Emalahleni; and Rustenburg.

Hydrogen sulphide (H₂S) is a colourless, flammable, hazardous gas with a strong odour of rotten eggs. It is produced by the breakdown of animal wastes or manure. It is heavier than air and can collect in low-lying and enclosed, poorly ventilated areas such as reception pits, ditches or manholes. Exposure to hydrogen sulphide may cause irritation to the eyes and respiratory system. Hydrogen sulphide is used in many industries.

Sulphur dioxide (SO₂) is a colourless gas with a characteristic, irritating, pungent odour. Exposure to sulphur dioxide may cause irritation to the eyes, nose and throat. Sulphur dioxide is used to manufacture sulphuric acid, paper, and food preservatives. 

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