Pharmaceutical pollution crisis revealed by Hout Bay’s mussels

Hout Bay’s marine environment is seriously threatened by pharmaceutical and personal care product compounds (PPCPs) that persist and bio-accumulate in marine life, even kilometres away from pollution sources, a new UCT study has revealed.

The findings raise urgent questions about sewage management, environmental monitoring, and public health in one of Cape Town’s most iconic coastal areas.

The research team, led by UCT’s postdoctoral research fellow Dr Cecilia Ojemaye, detected a range of PPCPs in mussel tissue samples collected at significant distances from the marine outfall and the Hout Bay River mouth. These compounds, residues from common medications and personal care products, enter the marine environment through human excretion, wastewater discharge, and improper disposal.

“The presence of these compounds in mussels is a red flag,” said Dr Ojemaye. “Mussels are sentinel organisms; they filter the water and accumulate pollutants, which means they are telling us a story about the health of the entire marine ecosystem.”

The study showed that the pollution plume from Hout Bay’s sewage discharges extends far beyond the immediate outfall area, contradicting previous assumptions that contaminants disperse quickly and harmlessly. Instantaneous modelling of bacterial indicators, such as enterococci, has been used in the past to justify the safety of marine outfalls. Still, researchers say this approach fails to capture the long-term build-up of persistent chemicals.

“This is not a case of ‘dilution is the solution to pollution’. These contaminants don’t just disappear; they spread, settle, and accumulate in marine life, creating an extensive and ongoing impact zone,” said Dr Ojemaye.

Hout Bay’s sewage system has long been a source of contention between residents, the municipality and environmental groups. Historical municipal decisions, including the choice of a marine outfall over land-based treatment, have been unpopular with local communities.

“The City has not provided Imizamo Yethu with adequate sanitation infrastructure for decades, leading to exceptionally high faecal content in the Disa River,” said co-author of the study, Professor Lesley Green, a professor of earth politics and director of Environmental Humanities South at UCT.

She added that they fully support the argument by lawyers involved in a court case against eThekwini for sewage pollution to the ocean, that “while floundering and excuse-prone, (the City) is nonetheless the local executive authority”. Prof Green further urged Cape Town to take a lead from the Minister of the Environmental Affairs, who “committed the country to protect marine biodiversity when he signed the UN Oceans 2025 pledge in Paris in June this year”.

The study highlighted that the marine outfall services about half of Hout Bay’s population, making it a significant source of chemical and microbial contamination. While the Hout Bay River also carries pollutants into the bay, the design and operation of the outfall itself contribute heavily to the problem.

Researchers warn that the situation poses both ecological and potential health risks to humans, especially if contaminated mussels and other shellfish are consumed. 

The bay lies within a marine protected area, making the findings particularly concerning for conservation efforts.

Beyond environmental damage, the research points to wider public health implications, including the possible spread of antimicrobial resistance through contaminated marine environments. 

“We urgently need to understand whether faecal coliforms in Hout Bay are carrying antimicrobial resistance genes. If so, this could have consequences for human health that extend far beyond our coastlines,” said Dr Ojemaye.

The study calls for a multi-pronged response, including investment in upgraded wastewater treatment, reduction of harmful chemical usage, and stronger regulations on pollutant discharge. 

“Hout Bay’s pollution problem is not unique, but it is urgent,” said Green. “This is an opportunity for innovation and collaboration. With the right technologies and political will, we can turn wastewater from a hazard into a resource.”

In response to the study findings, the City’s Deputy Mayor and Mayoral committee member for spatial planning and environment, Eddie Andrews, has since said:

"The challenge of the removal of pharmaceutical and personal care products (PPCPs) from wastewater is by no means unique to Hout Bay or Cape Town. Wastewater treatment works globally do not generally effectively remove contaminants of emerging concern (CECs) from sewage, irrespective of the level of treatment.

"The removal of CECs from municipal wastewater is complex due to their diverse chemical structures, low concentrations, and resistance to conventional treatment methods. Advanced treatment technologies such as ozonation, reverse osmosis, and membrane filtration can be utilised to remove some CECs, but implementation of these technologies can be expensive and energy-intensive and is not always a practical option at scale.

"Even our most sophisticated newly upgraded wastewater treatment works cannot treat wastewater in a manner that removes all traces of pharmaceuticals and other contaminants of emerging concern. The City recently undertook a comprehensive feasibility study to explore the options for replacing its existing marine outfall pipelines with new wastewater treatment works, and has reported on the outcomes of this study in various public forums. No decision has yet been made on the timing of the replacement of the outfalls with new treatment works."

The recent study by Dr Ojemaye et al. (2025) did not, in fact,  assess the volumes of pharmaceutical and personal care products (PPCPs) discharged via the marine outfall pipeline and could not have found that PPCPs were detected in significant volumes in effluent."

The source referred to (a report by the CSIR in 2016, available for download from the City’s website at this link) detected 21 PPCPs in Hout Bay wastewater but did not make any findings on the significance of the concentrations or loading. The same study found that “Non-steroidal anti-inflammatory drugs were not detected in the tissue of mussels or rock lobsters collected along the Cape Peninsula in 2016.” The other source cited by the authors for this claim is a 1995 Water Research Commission assessment of methods for determining dilution effectiveness, which has no relevance to the statement about recent studies on PPCPs.

In 2022, the City commissioned a more wide-ranging assessment of PPCPs in its coastal waters (CSIR, 2022, on our website at this link) which found in summary that “the impact of the discharges on shoreline waters was limited at the time of the surveys” and that the “number of pharmaceutical compounds found, and their total concentration was […] fairly low at Hout Bay Beach inshore of the Hout Bay outfall. The compounds found at Hout Bay Beach were more likely from the Hout Bay River outflow (10 compounds were found in the river in winter and 17 in summer). The CSIR study also found significant contamination in the Hout Bay River, and calculated hazard quotients for pharmaceutical compounds in the river at levels greater than those on the Hout Bay beach.

"Please note that none of the above responses should be taken to suggest that the City is not concerned about the effects of pollution in our marine and coastal environments – we must acknowledge though that Cape Town has many underserviced areas requiring the provision and upgrading of basic services, and must weigh up the prioritisation of limited funding in this context. The Environmental Monitoring Programme for the marine outfalls includes, in the 2026/2027 financial year, the sampling of both water and tissue at sites near the marine outfall to provide insight into this issue."

"The City of Cape Town, in 2024, commissioned independent experts to prepare a very comprehensive Environmental Monitoring Programme for all three of its marine wastewater outfalls. This Programme was approved by the Department of Forestry, Fisheries and the Environment, and is currently being implemented. It incorporates monitoring of hundreds of different parameters, including water quality (faecal bacteria, nutrients, metals, and physical parameters); water toxicity; sediment quality; bioaccumulation of contaminants in mussels, fish, and rock lobsters; ecological effects (habitat and invertebrate surveys); and contaminants of emerging concern (microplastics, pharmaceuticals and personal care products, and others).

"The findings of this intensive assessment are presented quarterly to a publicly accessible Permit Advisory Forum established by the City in April last year, and inputs and debate by members of the public, as well as the experts and civil society representatives who serve on the Forum, are encouraged at these meetings. We look forward to the first annual report on these studies, expected towards the end of the year.

"This programme builds on decades of monitoring by the City of the environmental impacts of the outfalls, all of which is comprehensively reported on in documentation available on the City’s website. City officials have also attended various public meetings in Hout Bay in the past year, at which these matters have been presented and discussed.

"Respectfully, the authors of the study appear to be doing no more than speculating when they state that the marine outfall does not achieve the dilution and dispersal of contaminants of emerging concern. Their work did not include an analysis of PPCPs in effluent, river water or in coastal waters, and analysed only mussels found in situ in the coastal environment. This study cannot conclude as to the source of the contaminants or the extent of the impact zone of the marine outfall, nor the effectiveness of its design, based on the methods and results presented. We look forward to engaging further with the authors in an appropriate forum on various concerns we have with the extensive conclusions they have drawn from a very limited study that did not investigate all of the aspects captured in its conclusions.

"What we do know is that the impacts of wastewater discharge, whether it occurs intentionally or due to spills, are far more acute in freshwater systems with very small volumes than they are in the highly dynamic offshore environment when dispersion and dilution take place after discharge through an outfall diffuser. As noted in the previous response, we have commissioned extensive research that we hope will provide greater insight into the questions raised here about the long-term impacts of marine wastewater disposal.

"We cannot agree that the marine outfall has been disregarded, either by the public or by the municipality. As described above, we have, over several decades, been monitoring its environmental impacts and reporting periodically on these in the form of comprehensive technical reports available on the City’s website, as well as in the scientific literature and in public engagements, including the Permit Advisory Forum.

"The City will act on reliable data and findings – to date, the extensive scientific work undertaken has not demonstrated a significant negative impact. The 2024 Marine Outfalls Environmental Monitoring Programme is very comprehensive and incorporates the assessment of hundreds of parameters, including several new components not previously forming part of routine assessments.

"The City acknowledges that the Hout Bay River is in a very poor state due to periodic and ongoing pollution from a variety of sources. It receives flows from a catchment of approximately 37 square kilometres, which includes natural upper slopes in the Table Mountain National Park, formal residential areas and smallholdings on both sides of the Hout Bay River, formal housing with backyard dwellers in Imizamo Yethu and Hangberg areas, and informal dwellings in Imizamo Yethu, which includes a fairly large informal settlement with limited services.

"The City’s 2024 Inland Water Quality Report notes that the main sources of water pollution in the catchment include (in no particular order) smallholdings and horses, sewage overflows from blocked pipes and pump station failures, mainly in the middle to lower reaches of the catchment and often linked to disposal of foreign objects into the sewer system (see for example this link on the impact of wet wipes on sewer infrastructure), and input and runoff of sewage-contaminated water into the stormwater system from the largely informal Imizamo Yethu settlement, which flows into the lower reaches of the Hout Bay River. The E. coli counts during routine inland water quality sampling by the City in the Hout Bay River near the Hout Bay beach are historically consistently high in relation to the recommended thresholds described in the 2024 Inland Water Quality Report.

"Coastal waters at Hout Bay Beach are monitored regularly, and coastal water quality data are readily available and regularly updated on the City’s website.

"The City’s coastal water quality sampling confirms that bacterial contamination at the Hout Bay beach is not typically at unsafe levels during the summer months, but remains consistently above zero for most of the year. The Hout Bay River flows throughout the year, and its inputs of urban runoff and sewage-derived contamination – together with more minor stormwater outflows – are likely the most significant causes of poor coastal water quality in Hout Bay. In weekly sampling data from the past eighteen months, there is a clear association between rainfall events and a decline in coastal water quality. This is apparent for both summer and winter, and aligns with data from elsewhere in Cape Town and from other cities globally, where bacterial contamination of coastal waters tends to increase for a period following rainfall.

"The potential health risks associated with swimming in the sea near river mouths or stormwater outflows, even in summer and especially after rainfall events, are signposted on the Hout Bay Beach, and are regularly communicated to the public and beach users. We do not recommend swimming in the sea near river mouths or major stormwater outlets, nor for 12 to 24 hours following significant rainfall.

"We concur with the authors of the study that further research into the bioaccumulation of pharmaceutical compounds by bivalves in a marine protected area is needed, and note that the City’s environmental monitoring programme for the marine outfalls includes such monitoring. We look forward to receiving the results of these studies in due course.                                                                  

"Should a risk assessment conclude significant risk to consumers or communities, the City will of course, respond accordingly. Unfortunately, the authors of the study made no effort to assess the risks posed by the pharmaceutical concentrations they determined, but simply state that exposure would be ‘harmful’. Pharmaceutical compounds have been found in marine mussels in coastal regions globally, and as the authors note, the Hout Bay data they present “aligns with trends seen in other global coastal environments exposed to urban wastewater pollution.”

"To determine the actual risk to consumers, it is necessary to establish the amount of seafood that would have to be consumed to cause an exposure over safe levels. As this was not undertaken and only the absolute concentrations are presented, it is simply not responsible or scientifically sound to conclude that this may result in harm. By way of illustration, at a dry weight concentration of ~43 nanograms per gram of mussel tissue (which is the upper limit detected in their research), a rough calculation suggests that the tissue of around 3 million mussels would be necessary to yield the same quantity of acetaminophen contained in a single Panado (500 mg). It is also of some concern that the authors do not appear to have accounted for the age or size of the mussels sampled in their study – the rates of accumulation of these compounds may vary with age.

"Finally, globall,y there are not yet established measures of when these CEC’s (which are now ubiquitous in our environments) are considered at a level that is harmful both to people and the environment.  The City remains engaged in this emerging science as it develops globally. 

"Lastly, the City does not dispute the presence of CECs in mussels. The City does however, request that, and based on the sweeping claims and conclusions made (especially those made in relation to public health), the authors take more responsibility in their application and improvement of scientific rigour in terms of their analysis and interpretation of the results of the study."

The City’s Mayoral committee member for water and sanitation, Zahid Badroodien, added:

"The City is committed to continually improving its wastewater systems. While the Hout Bay marine outfall currently operates within its design parameters and complies with national discharge regulations, we recognise that contaminants of emerging concern (CECs), including pharmaceutical and personal care products, pose new challenges globally, and that these are currently not treated in most municipal wastewater treatment works the world over.  Research regarding the treatment of CECs is ongoing throughout the world, and the City is evaluating multiple long-term options that may address this in the future at all of its wastewater treatment works, including the marine outfalls. Implementation of any of these options will be dependent on the outcomes of the feasibility studies, environmental processes, and budgetary constraints.

"The City has strengthened its public engagement and transparency mechanisms around the marine outfalls through regular Permit Advisory Forums (PAFs), where internal and independently audited environmental monitoring data are presented and discussed.

"The Hout Bay marine outfall’s performance and environmental impacts are shared transparently with stakeholders, and the forums serve as platforms for community feedback and discussion."

"The next PAF is scheduled for Friday, August  22, where the latest monitoring data will be presented. These forums form part of the City’s broader commitment to inclusive and science-based decision-making for wastewater management.

"The City is committed to ensuring equitable access to sanitation services for all residents, including those living in informal settlements like Imizamo Yethu. However, service delivery in Hout Bay is often impacted by factors such as challenging terrain and significant unplanned densification, which complicate infrastructure maintenance and upgrades."

Sewer challenges in Hout Bay

Several structural and behavioural challenges contribute to ongoing sewer overflows in the area:

• Unplanned densification in informal areas leads to a significant increase in wastewater volumes beyond the original sewer system’s capacity.
• Illegal informal dwelling connections to the sewer network, which compromise the integrity of the infrastructure.
• Stormwater-to-sewer cross-connections, implemented historically to reduce river pollution, now also contribute to system overloading.
• Widespread misuse of the sewer system, including the disposal of foreign objects, building rubble, and general waste that causes blockages and spills.
• Structures built over sewers make routine maintenance extremely difficult.

The Water and Sanitation Directorate has a dedicated regional team that focuses on sewer reticulation challenges in Hout Bay. This team has analysed root causes and implemented a range of short-, medium-, and long-term interventions, including:

Short-term interventions:

• Increased proactive cleaning and rapid response to spills, which has reduced the frequency of blockages year-on-year.
• Door-to-door inspections by the Water Pollution Control Unit, with enforcement actions where bylaws are violated.
• Ongoing education and awareness campaigns in Imizamo Yethu to curb misuse and promote better understanding of sewer system limitations.
• Adjustments to stormwater and detention pond systems to reduce the volume of diverted water entering the sewer network.
• Leak detection and repair to reduce unnecessary flows into the sewer system.
• Review and upgrade of City-serviced sanitation facilities to prevent spillages into stormwater.

Medium-term:

• The City is exploring the possibility of Victoria Road Pump Station pumping directly into the bulk main along the western boundary of the river (or at least split flows). If found to be effective and when resources/ tenders can be sourced, this would be a temporary measure.
• Our Catchment, Stormwater and River Management (CSRM) branch is also investigating the feasibility of inline treatment for water re-introduction, and possibly closing the low flow diversions, as this is placing a lot of strain on the sewer network.

Long-term:

A master plan item has been identified to potentially upgrade the 300mm sewer pipe running on the eastern boundary of the Disa River into the 525mm. This would affect the area from Riverside Terrace up until Disa River Pump Station (about 4km of pipe). Funding is projected to be available in the 2028/2029 financial year for the feasibility phase. This investigation and feasibility study for the project will include:

• PSP appointment (Professional Service Provider)
• Flow studies for pipe sizing
• Multiple route analysis to understand if current alignment if best due to access constraints and land ownership
• Environmental Impact Assessment
• Possibility of a sand trap
• Land surveying
• Mechanical input and sizing
• Possible land expropriation as the current main traverses private property with no servitudes
• Access roads to be constructed for ease of access

In addition, the City has a Pollution Abatement Strategy Action Plan (PASAP) in place, which is reviewed and updated quarterly by the CSRM branch, in partnership with community members through the Hout Bay River Community Forum (HBRCF). This is an active platform available to the public to play a significant role in addressing challenges and tracking progress on the interventions detailed above.

Infrastructure improvements currently underway:

• Installation of an additional pump at Victoria Bridge Pump Station to increase operational resilience.
• Upgrades to screens at the Disa Road Pump Station to better manage solid waste and foreign materials.

City-wide investment context:

As part of a broader R1,25 billion investment in sanitation infrastructure this financial year, R355 million has been allocated for sewer pipe replacements and R241 million for pump station upgrades across Cape Town.

Through this combined infrastructure and behaviour-change approach, the City aims to significantly reduce sewer spills and associated pollution into the Hout Bay River and adjacent marine environment.

CECs are present in all wastewaters in all towns, cities, and metros throughout South Africa and indeed the world over, and are not specific to Hout Bay's wastewater.

Cape Times