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An ambient air quality monitoring station is now in place to better monitor air quality around Milnerton Lagoon and share this information with the public as part of the City’s broader efforts to restore the lagoon environment. By the end of July, the temporary station at the Woodbridge Island Complex will move to a permanent location at the Milnerton Canoe Club parking area, becoming the 14thstation in the City’s Air Quality Monitoring network across Cape Town.
Since the installation of the monitoring station in February 2025, the SSB has detected varying levels of Hydrogen Sulfide (H₂S), all of which are below the World Health Organisation’s (WHO) health effects guideline of 150micrograms/24hours.
‘We acknowledge the smell nuisance caused by H₂S, and the monitoring data confirms the community’s experience. This monitoring is part of the City’s broader efforts to protect public health and transparently share critical information with residents as we work to restore the environment at Milnerton Lagoon,’ said Mayoral Committee Member for Water and Sanitation, Councillor Zahid Badroodien.
What is Hydrogen Sulphide?
H₂S is known as a so-called nuisance gas due to its characteristic rotten egg odour, which humans can detect even at extremely low concentrations. The gas is colourless, flammable, and toxic especially in high concentrations in confined spaces. It can be found in various environments, including sewer systems, oil and gas industries, and also as a by-product of certain industrial processes.
As South Africa does not have an ambient air quality standard for H₂S, the City utilises WHO guidelines.
Monitoring and results
The temporary station is a mobile mini-laboratory, equipped with a continuous ambient air quality analyser. This analyser measures H₂S levels 24/7, taking readings every 10 to 15 seconds. Data is automatically stored and analysed to assess exposure against international standards.
Key findings from 100 days of data indicate that while foul odours may be experienced at times, there were no exceedances of the World Health Organisation’s 24-hour average health guideline. Should residents experience any worrying symptoms we encourage residents to consult their local health practitioner when required.
Making readings available to the public
The City is also engaging the National Department of Forestry, Fisheries and the Environment and the South African Weather Service to publish H₂S readings on the South African Air Quality Information System SAAQIS platform for public access. The benefit of this will be that the public will have direct access in real time to the data published on the site, either via the SAAQIS App, which is downloadable free of charge to your cell phone either via your Android or IOS App Store or via the SAAQIS website available at https://saaqis.environment.gov.za/
In addition to this station at Woodbridge Island, the SSB has 13 other locations where they are monitoring air quality namely: Athlone, Atlantis, Bellville South, Bothasig, Cape Town – Foreshore, Goodwood, Khayelitsha, Molteno, Plattekloof, Somerset West, Potsdam, Table View and Wallacedene.