The dire state of SA rivers — What pollutants are lurking in the water?

A University of Johannesburg (UJ) study has uncovered dangerously high levels of cancer-causing chemicals in the Klip River in Gauteng.

The research highlights a serious environmental and public health threat, as the detected levels of polycyclic aromatic hydrocarbons (PAHs) exceed safe limits.

According to UJ researchers, sediment samples collected from the Klip River during the high and low flow seasons were found to contain 16 chemicals listed by the US Environmental Protection Agency as priority PAHs, with the varying concentrations depending on pollution level at different sites.

The study found that high molecular weight PAHs were more prevalent than low molecular weight PAHs, posing a greater environmental risk.

Most PAH concentrations exceeded the maximum permissible limits set by the Agency for Toxic Substances and Disease Registry, raising red flags for aquatic life, livestock and human health.

‘Disrupts entire ecosystems’

Dr Mathapelo Seopela, a lecturer and researcher in UJ’s department of chemical sciences, said the impact of pollutants spread on the environment.

“Sediment acts as a sink – every time waste is dumped, it accumulates in the riverbed. Due to the interaction between sediment and water, contaminants can easily transfer into the water column,” said Seopela.

“This doesn’t just affect people who consume the water; it also disrupts entire ecosystems, including aquatic organisms. If someone regularly eats fish from this river, their exposure to these toxic compounds becomes cumulative.”

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The UJ study, which was recently published, has been ongoing since 2021, traced the source to petroleum combustion, pyrogenic and petrogenic sources linked to human activities near the river.

The study also found alarming impacts on embryo development. Key findings included severe malformations, reduced hatch rates and high mortality in zebrafish embryos.

Seopela said there was strong correlation between high PAH levels and embryonic deformities and the potential health risks to livestock, agriculture and humans relying on the river for water or food.

“We observed toxic responses and developmental malformations in zebrafish, a model species with genetic similarities to humans.

The abnormalities we recorded in these fish suggest that humans exposed to the same pollutants could experience similar health effects,” she said.

“It’s a dynamic issue influenced by human activity, seasonal changes and how contaminants move within the water system. Since rivers are interconnected, pollutants dumped upstream can travel far downstream, affecting multiple communities. We want to use the study to addressing its societal impact.”

River polluters should ‘face the law’

Environmental activist and WaterCAN manager Ferrial Adam emphasised the widespread issue of river pollution in SA.

“This research report highlights the dire state of our rivers across the country. This is not just a Johannesburg problem – many of our rivers are in crisis. A WWF study found that 60% of South Africa’s river ecosystems are under severe threat, mainly due to pollution and human activities,” Adam said.

Adam called for stricter enforcement of environmental laws and harsher penalties for polluters.

“We need to push for stronger government action. Those who pollute our rivers – whether industries, government entities, or individuals – should face legal consequences, including jail time,” she said.

She also pointed out the lack of long-term data on water contamination, which makes it difficult to assess the full extent of pollution.

“We tend to study river pollution in isolated snapshots rather than looking at the bigger picture. We need nationwide, coordinated research to fully understand the scale of water contamination and its long-term effects,” Adam concluded.

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