Fish in a major South African river are full of microplastics

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We live in the age of plastic. Plastics are literally everywhere: clothes, furniture, computers, phones and more contain plastics. No wonder the food we eat, the water we drink, and even the air we breathe are contaminated with microplastics.

These tiny plastic particles have a diameter of less than 5 mm. Some, known as secondary microplastics, are formed from the breakdown of larger plastic items. In natural environments like rivers, plastics are exposed to different degradation processes driven by thermal, chemical, microbial and mechanical forces.

Primary microplastics, on the other hand, are manufactured to a microscopic size to be used, among other things, in the form of fibers, films, foams and granules. It is estimated that between 0.8 and 2.5 million tonnes of microplastics are released into the global marine system each year.

Once in the oceans, lakes, rivers and other water bodies, microplastics absorb toxic elements and organic contaminants. Their small size and large surface area means that microorganisms such as bacteria and fungi can also attach and colonize them. All of this makes microplastics a cocktail of contaminants.

Globally, research on microplastics is still in its infancy, as the scale of the problem has only become apparent in recent years. The knowledge gap is particularly high in Africa. This is worrying: the continent is home to some of the largest and deepest lakes and rivers in the world, but not much is known about the extent of microplastics in African freshwaters.



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It is also difficult to assess the environmental and public health risks associated with microplastics. Indeed, scientists are still learning how microplastics move through various pathways and where people are most vulnerable to exposure.

In an attempt to fill this gap, we recently studied common carp collected from the Vaal River in South Africa. It is an important freshwater body of great economic value which, according to the country’s Department of Water and Sanitation, “supports almost 50% of South Africa’s gross domestic product” . The river provides water for drinking, agriculture and industries and services to around 11 million people in Gauteng, Mpumalanga, North West and Free State provinces.

Our findings were disturbing. We took samples from the digestive tract of 26 fish and found a total of 682 particles, ranging from seven to 51 particles per fish. This means that the river is significantly polluted with microplastics. This isn’t just bad news for people’s health; it also has huge economic implications as the Vaal and similar bodies of water are used for agriculture, ranching and recreation.

Toxicity and risk

South Africa has a vibrant plastic manufacturing industry. Recycling, however, is limited. The country is ranked among the top 20 countries with the largest mass of mismanaged plastic waste – and a notable proportion of this enters the aquatic environment.

Many of the microplastics we recovered in our samples were small, colored (dyed), and fibrous (particles look thin and elongated). These are concerning characteristics as studies have shown that several aquatic organisms are attracted to and consume small, colorful and fibrous microplastics, which resemble natural prey.

Their larger surface area means smaller microplastics absorb more pollutants from water than their larger counterparts, leading to additional health risks. Research has also found that the smaller the microplastics, the more likely they are to end up in the muscles and liver of aquatic organisms. This makes them more harmful to animals. And their fibrous form means they are easily embedded into tissues. They therefore spend more time in an animal’s intestines and become more toxic.

Finally, colored microplastics are particularly toxic due to the dyes used in the plastic manufacturing process.

Raising awareness and improving policies

Many people simply don’t know what microplastics are or how they might cause harm. While sampling, we encountered people fishing; others cooked and ate fish along the banks of the Vaal River as they fished. They were interested to know what we were doing and admitted that they had never heard of this problem before.

People cook freshly caught fish on the banks of the Vaal River.
Dalia Saad

This highlights the importance of social awareness and public education. Public awareness strategies could include a wide range of activities designed to persuade and educate, perhaps beginning with early primary school curricula. It is important to extend the message beyond reuse and recycling to responsible use and waste minimization. People should also be made aware of the risks of using plastic for water or food storage.



Read more: Nigeria’s plastic pollution is harming the environment: Action to tackle it is overdue


Raising awareness of these issues is key to creating public pressure to demand effective waste regulation. This is important because the negative effects of microplastic pollution are not limited to the biophysical elements of the environment – ​​they have implications for social and economic systems.

Rivers and lakes are used for transportation, agriculture, livestock and recreation. The productivity, viability, profitability and safety of these sectors are highly vulnerable to plastic pollution. Microplastic pollution is as much a social concern as it is a scientific one.

The author would like to thank her students who conducted the study with her: Patricia Chauke, Gibbon Ramaremisa and Michelle Ndlovu.

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