Pollutants discovered in Hout Bay

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

- Sheree Bega

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 postdoctoral 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 excrement, wastewater discharge and improper disposal.

The findings revealed significant levels of sewage-related pollutants in the sampled environments, with concentrations ranging from 32.74 to 43.02 ng/g [nanograms per gram] dry weight for acetaminophen [paracetamol], up to 384.96 ng/g for bezafibrate [an antilipemic agent that lowers cholesterol and triglycerides], and as high as 338.56 ng/g for triclosan [a broad-spectrum antimicrobial agent].

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 buildup 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.”