Fish in Vaal River 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 the food we eat, the water we drink and the air we breathe are contaminated with microplastics.

The tiny plastic particles are smaller than 5mm in diameter. 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 are manufactured at microscopic size to be used as fibres, films, foams and pellets, among other things. It is estimated between 0.8 and 2.5-million tons of microplastics are released into the global marine system per year.

Once they’re in oceans, lakes, rivers and other bodies of water, microplastics absorb toxic elements and organic contaminants. Their small size and large surface area mean microorganisms such as bacteria and fungi may also attach and colonise on them. This all makes microplastics a cocktail of contaminants.

Globally, microplastics research is in its infancy as the scale of the problem has only become apparent in recent years. The knowledge gap is especially high across Africa. That’s worrying because the continent is home to some of the largest and deepest lakes and notable rivers, but not much is known about the extent of microplastics in African freshwaters.

It is also difficult to assess the environmental and public health risks linked to microplastics. That’s because scientists are learning about how microplastics move through pathways and where people are most vulnerable to exposure.

In an attempt to bridge this gap, we recently studied common carp fish collected from Gauteng’s Vaal River. It’s a major freshwater body of significant economic value which the department of water and sanitation says  “supports almost 50% of SAs gross domestic product”. The river supplies water for drinking, agriculture and industries and services around 11-million people in Gauteng, Mpumalanga, North West and Free State.

Our findings were troubling. We took samples from 26 fish 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 only potentially bad news for people’s health. It also has huge economic implications because the Vaal and similar water bodies are used for agriculture, breeding livestock and recreation.

Toxicity and risk

SA has a vibrant plastic manufacturing industry but recycling is limited. The country is ranked among the world’s top 20 countries with the highest mass of mismanaged plastic waste, and a notable proportion of that enters the aquatic environment.

Many of the microplastics we recovered from our samples were small, coloured (dyed) and fibrous (the particles have a slender and elongated appearance). Those are worrying characteristics because studies have shown several aquatic organisms are drawn to and consume small, coloured and fibrous microplastics which resemble natural prey.

Their greater surface area means smaller microplastics absorb more pollutants from the water that 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. That makes them more harmful to the animals, and their fibrous shape means they are easily embedded in tissue. This mean they spend longer in an animal’s intestines and become more toxic.

Coloured microplastics are particularly toxic because of the colouring agents used during the plastic manufacturing process.

Awareness and improved policies

Many people are not aware of what microplastics are, nor how they might cause harm. During sampling we met people who were fishing, cooking and eating fish along the banks of the Vaal River. They were interested to know what we were doing and admitted they had not heard about the issue.

This emphasises 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 grade school curricula. It is important to extend the message beyond reusing and recycling to the responsible use and minimisation of waste. People should also be taught about the risks involved in using plastic for water or food storage.

Making people aware of these issues is key to creating public pressure to demand effective waste regulations. This is important because the negative effects of microplastic pollution are not limited to the bio-physical elements of the environment. They have implications for social and economic systems.

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

Dalia Saad is a researcher at the school of chemistry, University of the Witwatersrand, University of the Witwatersrand. Additional information sourced by students Patricia Chauke, Gibbon Ramaremisa, and Michelle Ndlovu.

• This article was first published by The Conversation