Freshwater fish highlight SA rivers are full of microplastics

We are living in the plastic age. Plastics are literally everywhere: clothes, furniture, computers, phones and more contain plastic materials.

It’s no wonder, then, that the food we eat, the water we drink and even the air we breathe are contaminated with microplastics.

These tiny plastic particles are smaller than five millimetres in diameter.

Microplastics are everywhere

Some, known as secondary microplastics, are formed from the breakdown of larger plastic items. In natural environments, such as rivers, plastics are exposed to different degradation processes driven by thermal, chemical, microbial and mechanical forces.

Primary microplastics are manufactured at microscopic size to be used as fibres, films, foams and pellets. It is estimated that between 0.8 million and 2.5 million tons of microplastics are released into the global marine system per year.

Once they’re in bodies of water, microplastics absorb toxic elements and organic contaminants.

Their small size and large surface area mean microorganisms such as bacteria and fungi also attach and colonise them. This makes microplastics a cocktail of contaminants.

Globally, microplastic research is still in its infancy as the scale of the problem has only become apparent in recent years.

Africa is home to some of the largest water bodies in the world

The knowledge gap is especially high in Africa. The continent is home to some of the largest and deepest of the world’s lakes and notable rivers, but not much is known about the extent of microplastics there.

It is difficult to assess the environmental and public health risks because scientists are still learning about how they move through various pathways and where people are most vulnerable to exposure.

In an attempt to bridge this gap, we studied carp fish collected from the Vaal River. The department of water and sanitation says it ‘supports al-most 50% of South Africa’s gross domestic product”.

It supplies water for drinking, agriculture and industries and services to around 11 million people in Gauteng, Mpumalanga, North West and the Free State.

The findings were troubling. We took samples from 26 fish’s digestive tracts and found a total of 682 particles – ranging from seven to 51 particles per fish.

That means the river is considerably polluted with microplastics. This isn’t just potentially bad news for people’s health; it also has huge economic implications because the Vaal and similar water bodies are used for agriculture, livestock and recreation.

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

Microplastics resemble natural prey

Many of the microplastics we recovered were small, coloured (dyed) and fibrous (the particles
have a slender and elongated appearance).

Those are worrying characteristics because such microplastics resemble natural prey for some aquatic organisms.

Their greater surface area means smaller microplastics ab-sorb more pollutants from the water than their larger counterparts, resulting in additional health risks.

Research has also found the smaller the microplastics, the more likely they are to end up in aquatic organisms’ muscles and livers. Their fibrous shape means they’re easily embedded in tissue.

So they spend longer in an animal’s intestines and become more toxic. Coloured microplastics are particularly toxic because of the colouring agents.

Many people are simply not aware of what microplastics are, nor how they might cause harm. During sampling, we met people who were fishing; others were cooking and eating their catch while they fished.

They were interested to know what we were doing and admitted they’d not heard of this issue before. This emphasises the importance of social awareness and public education.

Public awareness strategies could include activities designed to persuade and educate, perhaps beginning with early grade school curricula.

It is important to extend the message beyond reuse and recycling to the responsible use and minimisation of waste.

Making people aware of these issues is key to creating public pressure to demand effective waste regulations.

Rivers and lakes are used for transport, agriculture, breeding livestock and recreation. The productivity, viability, profitability and safety of these sectors are vulnerable to pollution.

Microplastic pollution is as much a social concern as it is a scientific one.

Saad is researcher, School of Chemistry, University of the Witwatersrand.
Patricia Chauke, Gibbon Ramaremisa, and Michelle Ndlovu helped conduct the study.

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