At Isinuka Springs near Port St Johns, the pink water bubbling from the earth is believed to have healing and protective powers.
People come to the sulphur-rich sacred springs to bathe, cleanse themselves spiritually and collect water and sediments. Some sell the water and sediments to passing motorists and tourists.
Now researchers have found that the sacred springs are carrying another, less visible burden: microplastic contamination.
Researchers from Rhodes University, the National Research Foundation and the University of the Witwatersrand sampled four sites at Isinuka in the Eastern Cape and five carbon dioxide-seeping freshwater systems along the Bongwana Fault in March 2025.
Across the nine sites, they found 184 microplastic particles, with concentrations ranging from five to 48 particles a litre and an average of about 20.4 particles a litre. The highest concentration was recorded at Site 1 at Isinuka, the most intensively used of the sites.
In their study, the researchers said the relatively high concentration at the site “may be associated with its greater accessibility and the variety of human activities reported at the site”, including ritual bathing, spiritual cleansing, drinking, tourism and commercial activities.
The findings at Isinuka did not surprise lead author Thendo Mutshekwa, a research associate at Rhodes University who is affiliated with the Albany Museum.
“The springs are intensively used by communities and visitors,” he said. “People use them for drinking, bathing, spiritual cleansing, traditional healing and other cultural practices. We also observed littering within and around the Isinuka springs, which shows that these sites are not completely free from human pressures.”
What was more interesting, he said, was finding microplastics even at sites that looked clean and were more remote.
“We found microplastics at all nine sites we sampled, with between five and 48 particles per litre. This shows that water can look clean to the naked eye but still contain very small plastic particles that we cannot see.”
At Isinuka, the researchers found 48 particles per litre at the main site they sampled.
“We think the high level may be linked to the large number of people visiting and using the spring,” said Mutshekwa.
However, the study did not trace the particles to specific sources.
“They could come from littering, human activities, rainfall and runoff, tourism, or even the atmosphere,” Mutshekwa said.
The study is the first baseline assessment of microplastic contamination in these sacred freshwater systems and is intended to provide a starting point for further research.
The authors noted that while microplastics were increasingly being found in freshwater ecosystems, culturally significant and geochemically unusual places, such as Isinuka Springs, had received little scientific attention.
The sampling was conducted during the rainy season, when runoff and erosion can increase the movement of microplastics from land into freshwater.
The researchers found that fibres and filaments dominated, accounting for 69.6% of the particles, followed by fragments at 21.7%.
Transparent particles were the most common colour, making up 38.6% of the total, while particles larger than 20 micrometres accounted for 51.1% of those detected.
Polypropylene was the most frequently identified polymer, making up 38% of the analysed particles, followed by polystyrene at 30%, polyethylene terephthalate at 15% and polyethylene at 12%.
The polymer findings apply only to particles larger than 20 micrometres and to a random subsample of about 60% of suspected particles. Smaller particles could not be polymer-confirmed because of limitations of the analytical equipment.
The researchers also took precautions against contamination during sampling and laboratory analysis. No microplastic contamination was detected in their laboratory and field controls or procedural blanks.
The findings varied between the sites. The three Bongwana sites on private property or accessible only with permission had lower concentrations than Isinuka, which the researchers suggest might partly reflect their greater isolation.
Two sites at Nomkololwana village in Mbizana, however, had higher concentrations than the other carbon dioxide-seeping sites. The sites are also used for traditional practices and ancestral communication.
The researchers cautioned that the associations did not demonstrate that human activity was responsible for the differences. The study was described as a baseline assessment of microplastic contamination in the sacred freshwater systems, rather than a measure of long-term pollution.
Only one surface water sample was taken at each site and no replicate samples were collected. Restrictions imposed by some communities limited the researchers’ ability to collect replicates.
“The findings should be interpreted as baseline evidence of MP [microplastic] occurrence during the rainy season only and do not represent seasonal variability or annual contamination patterns within these freshwater systems,” the study said.
The study also did not examine microplastics in sediments or aquatic organisms, or investigate how the unusual chemistry of the sulphur-rich and carbon dioxide-seeping waters affects the transport, breakdown or retention of the particles.
The researchers said further work should include repeated sampling across seasons, a wider range of particle sizes and analysis of sediments and aquatic organisms.
For communities using the waters for drinking, healing and spiritual practices, the presence of microplastics is a concern. But Mutshekwa stressed that the study did not establish a health risk.
“Our study does not show that microplastics in these waters are causing health problems. We need more research before we can make that conclusion. However, their presence is a concern because people are directly using these waters.”
The research forms part of a larger project supported by the Water Research Commission, which brings together scientific research and Indigenous Knowledge Systems to examine how sacred water systems can be protected.
“We are interested not only in pollution but also in understanding how communities use, understand and protect these waters and how their knowledge can work together with scientific approaches to protect the springs,” Mutshekwa said.
He said protecting the springs should be a shared responsibility involving government, researchers, local authorities, conservation organisations and communities.
“I would like to see sacred springs included in regular water quality monitoring. We should also monitor them during different seasons and look at the water, sediments and aquatic organisms.
“Most importantly, scientific research should work together with Indigenous and local knowledge. Communities have used and protected these waters for generations, so their knowledge and experience are very important.”
The research also has a personal significance for Mutshekwa. Musa C Mlambo, who was his postdoctoral colleague at the time, first introduced him to the sacred springs. The two explored them together and developed the early ideas that eventually became part of the research.
Mlambo died before they could see the work through.
“We became interested in these places and explored them together for the first time. Musa played an important role in bringing these springs to my attention and in developing the early ideas around this work. Sadly, he passed away before we could see the full journey of this research.
“For me, this work is also a continuation of something that Musa and I started together. I hope we can build on that early work and continue studying and protecting these important freshwater systems.”