Microplastics on the Menu

Oct 11, 2017 | News

This article is the second instalment of the AMWN’s On the ground Showcase series. Read the first instalment here.

There’s no denying that plastic is a versatile and useful material. These days we don’t even think twice about the fact that some form of plastic is involved in most things we do on a daily basis, from using transport to brushing your teeth. But the one place you definitely don’t want plastics appearing is on your dinner plate. Alarmingly, research is showing that we may in fact be consuming “microplastics” when we tuck into our favourite seafood. The African Marine Waste Network spoke to Dr Holly Nel, microplastics researcher and project manager at the AMWN about her disturbing discovery on microplastics and mussels in South Africa, and what this means for the rest of Africa.


Crash course: What are microplastics?
Microplastics are plastic particles ranging in size from 5 millimeters to 1 nanometer (750,000 times smaller than the width of a human hair) and they fall into two categories. “Primary microplastics” are originally manufactured in small size, like microbeads for example, which are tiny plastic balls used in exfoliating facewashes. “Secondary microplastics” result when large plastic items are mechanically broken down into smaller pieces by UV radiation, wind, waves or animals.

The problem with plastics is that their breakdown in the ocean does not lead to a degradation of the plastic molecule – this means that plastic never “goes anywhere” it just degrades into smaller and smaller pieces but remains intact at microscopic scale. Even some plastics that claim to be biodegradable need very specific environmental conditions to breakdown completely – conditions that are rarely met in the marine environment. This effectively means that every piece of plastic we put into the ocean is there to stay.

Image source: Sherri A. Mason/State University of New York at Fredonia // Image source: Crystal51/ Shutterstock.com

So what’s the big deal?
Plastic may be useful, but it certainly isn’t appetising, and unfortunately it’s easily mistaken for food by aquatic animals and eaten. Large pieces of plastic can entangle animals or physically block their digestive systems causing death, as is often seen in birds and turtles. Plastics often contain a range of chemical additives that are added during their manufacturing process and these harmful substances can leach into marine organisms during digestion. Ingested chemicals can even “biomagnify” up the food chain, meaning that organisms at the top of the food chain (for example, the tuna we eat) can have greater levels of pollutants than those animals further down the chain.

Plastic can also sequester and concentrate toxins present in the environment. Lab experiments on animals show the potential adverse side effects of ingestion to include negative impacts on the immune system, on reproduction, on developing embryos, hormonal function and even consequences on a genetic level. However, the effects on humans have not yet been tested and are difficult to ascertain. Global plastic production is ever on the rise (in 2010 it was estimated that between 4.8 and 12.7 million tons ended up in the ocean) and research reports the growing presence and abundance of microplastics in the water of lakes and seas, in the sediments of rivers and deltas, and in the stomachs of various organisms ranging from zooplankton to whales, according to a UN report.

Main course:

Mussels with a side order of microplastics
Dr. Holly Nel recently explored the occurrence of microplastics along the South African coastline on a national scale, seeking to establish baseline data for future studies to compare their results to. Water and sediment samples were taken at sixteen beaches and results were immediately cause for concern: “… we found plastics at every single one of the beaches at really high concentrations and densities that were very similar to those that are found in the Northern hemisphere” says Nel, “… this really showed the extent of plastics and microplastics in the marine environment – that it’s really not a localised issue anymore.”

Nel’s next thought was that if microplastics are so prevalent, what is happening to the marine animals along this coastline? Her chosen study animal – the humble mussel, selected due to their natural process of constantly filtering water, and therefore potential continual exposure to microplastics. Mussels were collected and dissected from each of the beaches previously sampled. The results were conclusive: Nel found microplastics in all mussel samples at all of the sites. This suggests a high frequency of mussels containing microplastics in their tissues in South Africa. “The amount of microplastics (per gram of [mussel] wet weight) fell within the range of mussels, clams and oysters that scientists were testing in Europe, so again, we are no different to the more developed global polluted waters as we might assume” Nel commented. You might want to rethink the next time you’re about to dig into a mussel pot.

Image: Macroplastics found by Dr Nel at various South African beaches

In response to questions on the affect this will have on humans Nel said, “What’s really important is how it’s going to effect the mussel population. We rely on marine organisms for food security and… microplastics will have an effect on the population structure of a [marine] organism… As a large plastic item will clog up a bird, so will small plastics clog up zooplankton… it work’s the same way, just on a smaller scale. And if you affect the population structure of [these animals] you’re decreasing what we rely on for food.” Additionally, you alter finely tuned aspects of the marine ecosystem which can have knock-on effects for the entire environment.

What’s happening in Africa?

While South Africa has a range of scientists working on microplastics research, to our knowledge there is only one published paper in the rest of Africa that examined microplastics, specifically microplastic ingestion by fish in Lake Victoria. Nel laments this lack of research “because we are completely unaware of what the problem is with microplastics in the rest of Africa,” she says. Nel emphasises the need for research to fill this knowledge gap and to attract more funding for further research with more advanced equipment. The African Marine Waste Network seeks to promote these research initiatives in Africa through increased communication and collaboration, thus enabling better informed decisions in waste management. You can read more about data and research on marine debris in Africa and how to fill data gaps in the soon to be released Strategy document for Africa.

In the meantime, you can easily make changes to your own lifestyle to combat microplastics.


How do I make a difference?

  • Be more consumer conscious in your purchases.
  • Stop using microbead facewash.
  • Use reusable shopping bags, water bottles and coffee cups and skip the straw.
  • Recycle your waste.
  • Wash your clothes only when necessary and put filters on your washing machine to stop microfibers from clothing entering the water system.

Addtional resources:
UN report on Microplastics (2016)

Microplastics found in Canadian clams

Video: How much plastic is in the ocean?