Pharmaceuticals found in Hout Bay mussels

Hout Bay’s marine environment is threatened by pharmaceutical and personal care product compounds (PPCPs) that have accumulated in marine life, even kilometres from pollution sources, University of Cape Town (UCT) researchers have found. 

The authors said the findings of their study, published in the journal Environments, raise urgent questions about sewage management, environmental monitoring and public health in one of Cape Town’s popular coastal areas.

The research team, led by Cecilia Ojemaye, a post-doctoral research fellow at UCT, detected a range of personal care product compounds in mussel tissue samples collected at significant distances from pipelines discharging municipal wastewater and the Hout Bay River mouth. 

These compounds — residues from common medications and products such as shampoo, soap, toothpaste and moisturisers — enter the marine environment through human excretion, wastewater discharge and improper disposal.

The presence of these compounds in mussels is a “red flag”, Ojemaye warned. “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 pollution from Hout Bay’s sewage discharge extends far beyond the immediate outfall area, contradicting previous assumptions that contaminants disperse quickly and harmlessly. 

Modelling of bacterial indicators, such as enterococci, are used to justify the safety of discharges into the sea, but the researchers said this does not capture the long-term build-up of chemicals.

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

Sewage contamination

The researchers used chemical analyses to quantify the presence of pollutants such as personal care product compounds in sentinel marine organisms such as mussels, as well as microbial indicators of faecal contamination in river water and seawater, for estimating the extent of affected zones in the coastal environment of Hout Bay.

They also investigated the pharmaceuticals found in wastewater effluent samples in Hout Bay, examining whether these substances were also detectable in marine biota, specifically mussels. 

The findings revealed significant levels of sewage-related pollutants in the sampled environments.

“These results highlight persistent PPCP contamination in marine organisms, with increasing concentrations observed over time, suggesting a rise in population and pharmaceutical use,” the study said.

Microbial analysis also found high levels of E coli in the Hout Bay River, particularly near stormwater from the Imizamo Yethu settlement, with counts exceeding 8.3 million colony-forming units per 100 millilitres. 

“These findings underscore the significant impact of untreated sewage on the environment,” the study noted.

It concluded that sewage treatment is insufficient to mitigate pollution, urging the implementation of more effective wastewater management practices and long-term monitoring of pharmaceutical levels in marine biota to protect both the environment and public health.

In addition, municipal decisions regarding sewage disposal options in Hout Bay have played a significant role in the pollution by sewage of the coastal area. The lack of control of serviced land invasion has exacerbated things.

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

The authors fully support the argument by lawyers involved in a court case against eThekwini metro, KwaZulu-Natal, for sewage pollution in the ocean, that the city, as the local executive authority, is responsible for the problem. 

Significant source of pollution

They say the sewage outlet services about half of Hout Bay’s population, making it a significant source of chemical and microbial contamination.

The Hout Bay River also carries pollutants into the bay, but the design and operation of the sewage outlet itself contribute heavily to the problem. The situation poses both ecological and potential human health risks if contaminated mussels and other shellfish are eaten. 

That the bay lies in a marine protected area makes 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,” Ojemaye said. “If so, this could have consequences for human health that extend far beyond our coastlines.” 

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. 

This is especially critical in light of issues such as the Covid-19 pandemic, which saw increased chemical use, and the ongoing energy crisis, which affects wastewater management.

Outdated, harmful

Globally, marine outlets are increasingly recognised as outdated and environmentally harmful, the scientists said, and replacing them with land-based treatment facilities should be a priority. 

Such systems can remove pollutants more effectively as well as produce renewable energy and recover valuable resources from wastewater.

“Hout Bay’s pollution problem is not unique, but it is urgent,” Green said. “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.”

The research team emphasised that although further studies are needed to map the pollution zone’s full extent and understand the risks of consuming contaminated seafood, mitigation measures should begin without delay. 

“This is not just about science; it’s about protecting livelihoods, ecosystems and the health of our communities. If we wait until the damage is irreversible, it will be too late.”

The study is a wake-up call for Cape Town, Green said, urging policymakers and the public to face the uncomfortable truth that the city’s marine environment is absorbing the cost of inadequate wastewater management. “Without urgent intervention, the toxic tide will keep rising.”

City of Cape Town’s response

The difficulty of the removal of PPCPs from wastewater is not unique to Hout Bay or to Cape Town, said Eddie Andrews, the city’s deputy mayor and the member of the mayoral committee (MMC) for spatial planning and environment. 

“Advanced treatment technologies such as ozonation, reverse osmosis and membrane filtration can be used to remove some CECs [contaminants of emerging concern], 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 feasibility study to explore the options for replacing its marine sewage pipelines with new wastewater treatment works, but no decision has yet been made on when this will happen.

“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. 

Marine outfalls

In 2024, the city commissioned independent experts for its environmental monitoring programme for all three of its sewage outfalls. It incorporates monitoring hundreds of different parameters such as water quality and toxicity, sediment quality, bioaccumulation of contaminants in mussels, fish and rock lobsters, ecological effects and CECs (microplastics, personal care products, medication and others).

The findings are presented quarterly to a publicly accessible permit advisory forum established by the city in April last year, Andrews said. The first annual report on these studies is 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,” he said.

“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.” 

Andrews said the UCT study “cannot draw conclusions” about the source of the contaminants or the extent of the impact zone of the sewage outlet, nor the effectiveness of its design, based on the methods and results presented. 

“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,” he said. 

“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.”

The city will “act on reliable data and findings”, he said.

“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.”

Very poor state

The city acknowledges that the Hout Bay River is in a very poor state because of pollution from a variety of sources, Andrews said.

It receives flows from a catchment of about 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 potential health risks associated with swimming in the sea near river mouths or stormwater outflows, even in summer and especially after rainfall, are signposted on the Hout Bay Beach and communicated to the public and beach users. 

The city concurs with the study’s authors that further research into the accumulation of pharmaceutical compounds by bivalves in a marine protected area is needed, and note its environmental monitoring programme for the sewage outlets includes such monitoring.

“Unfortunately the authors of the study made no effort to assess the risks posed by the pharmaceutical concentrations they determined, but simply stated that exposure would be ‘harmful’. 

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 in excess of safe levels, Andrews said. “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.”

“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.”

The city does not dispute the presence of CECs in mussels but “requests 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 MMC for water and sanitation, Zahid Badroodien, said equitable service delivery in Hout Bay “is affected by factors such as challenging terrain and significant unplanned densification, which complicate infrastructure maintenance and upgrades”.

These include unplanned densification in informal areas, leading 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 and stormwater-to-sewer cross-connections, implemented historically to reduce river pollution, which now also contribute to system overloading.

The disposal of building rubble and general waste that cause blockages and spills, as well as structures built over sewers make routine maintenance difficult.

The water and sanitation directorate has a regional team that focuses on sewer reticulation problems in Hout Bay, Badroodien said. This team has implemented a range of short, medium and long-term interventions.

“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,” he said.

“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.”