The sacred Osun River in Nigeria has recorded the highest measured level of microplastics in a river in the world, and researchers are calling for a ban on single-use plastics.

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Yves Vanderhaeghen

Microplastics are everywhere, and Dr Gideon Idowu, an Environmental Chemist at Nigeria’s Federal
University of Technology Akure (FUTA), has conducted a massive research project across eight
African countries to understand their levels and impacts in riverine and marine systems.
Idowu and his team have published some of their findings in the “Journal of Hazardous Materials
Advances”, in an article titled “Why Nigeria should ban single-use plastics: Excessive microplastic
pollution of the water, sediments and fish species in Osun River, Nigeria”. Idowu said that “the levels
of microplastics that we found in the Osun River were very high, but for one of the sites, the levels
are really, really high, at 22,079 particles/litre”. The Osun River is a UNESCO world heritage site and
a vital water source for many communities in Southwestern Nigeria.
Over 300 million tonnes of plastics are produced every year around the world, and the OECD has
forecast that by 2060, fossil-fuel based plastics would amount to 1.2 billion tonnes, of which over
one billion tonnes may go to waste. Microplastics have infiltrated almost all environments and
organisms, and the particles, says the OECD, kills more than a million seabirds and 100 000 marine
mammals per year.
In response to the hazard, Greenpeace International has now called for a Global Plastics Treaty, and
newspaper headlines reflect public anxieties about the pervasiveness of microplastics: “We inhale a
credit card's worth of microplastics each week,” reports the BBC; “Potentially toxic microplastics are
found in 100 percent of human placentas tested by scientists,” reports the Daily Mail; “Microplastics
found in sediment layers untouched by modern humans,” reports Futurism; “Researchers find a
massive number of plastic particles in bottled water,” reports NPR.
Microplastics are fragments of any type of plastic less than 5 mm in size. Talking about microplastics
in river waters, Idowu said “Ordinarily, we wouldn't see the majority of them if we didn't put them
under the stereo-microscope that enabled us to detect and count them. You would probably just
think it's normal water that's a bit turbid. You wouldn't know that those things are there.”
Idowu’s study, which is funded by a Jennifer Ward Oppenheimer Research Grant of $150 000,
highlights how microplastics are formed from the breakdown of larger plastic items, as well as from
manufacturing processes that generate plastic pellets and nurdles. These tiny particles have been
found to wreak havoc on ecosystems, affecting organisms' physiological functions and reproductive
capabilities. They also have the potential to adsorb harmful chemicals, posing a threat to any
organisms that ingest them.
The study on Osun River was conducted to assess the overall levels of microplastics in the water,
sediments, and commercially important fish species in the river.
Sampling locations were strategically chosen along the river, including areas upstream and
downstream of the Oshogbo metropolis, with a population of over 714 000. Idowu said “the

particular site where we got the very high value happens to be close to the city centre, where people
throw in all sorts of waste, including plastics. It was difficult to access the river sediments in the first
place, because everything we lifted up was just one plastic item or the other. That tells you the
magnitude of pollution of the river, and probably explains why microplastic levels were extremely
high for that location, which was one of the five sampled locations on the river. But what we did not
expect was that the microplastics found at this location would be the highest reported so far, for a
river water globally, as it has now turned out to be”
The microplastics were of diverse types. Analyses revealed “seven polymer materials, including
acrylonitrile butadiene styrene (ABS) and ethylene vinyl acetate (EVA), that have not been
commonly reported for river environments.” Fish species crucial for local economies were also found
to be contaminated with microplastics, raising concerns about human consumption. “Microplastics
ranged averagely from 407 to 1691.7 particles in the gastro-intestinal tract (GIT) of six fish species
analysed, with silver catfish (Chrysichthys nigrodigitatus) having the highest concentration.” Idowu
said that while levels found in the fishes were higher than those reported for fishes in Asia and
Europe, they were “similar to other plastic pollution hotspots in Africa”.
Idowu noted that “across all the sites where we conducted research, we found that the countries
which recorded the highest levels of microplastics were Nigeria and Zimbabwe, and the lowest were
Kenya and Tanzania, where there have been some ban on single-use plastics”.
That is why “for us to see a significant reduction in the levels of microplastics in the environment,
there is a need to ban single-use plastics, like carrier bags and styrofoams. Our research indeed
confirmed that black particles from black carrier bags were abundant in the river environment.
There is a need to ban those categories of plastics because people just use them and throw them
away, they don't reuse. We need to shift to the type of bags that people can use again and again.
And where possible, there should be a substitution of this type of bags with paper alternatives”
Idowu said that while there are clear environmental impacts, as demonstrated by the presence of
microplastics in the gut of the fishes, there are also health hazards posed to humans. “People are
ingesting the microplastics when they consume the fish. Some sections of the river that we analysed
are also used for drinking. This clearly shows that people are consuming microplastic-laden water”.
“A ban on some plastics may reduce profits to the manufacturers, but the preservation of the
environment would be a win-win thing for Africa. We will have more vibrant aquatic systems, which
would support the growth of fish and other resources that serve as livelihood to some other people.
If we look at the slow pace of infrastructural development in Africa, it implies that many rural
communities would still depend on rivers for some years to come. We would reduce the level of
microplastics to which these people are exposed”
Idowu said that while the message is getting to the policymakers and the government of Nigeria, for
instance, is considering a ban on single-use plastics, he said “there are different forces, different
interests, and so a pronouncement has not been made yet for the whole of the country. But there
are individual states, where there have been bans”. “We emphasize the need for the Nigerian
government to ban certain single-use plastics, as a step towards reducing plastic pollution of

Nigerian rivers, that shelter important fish species and provide water for religious and domestic
purposes,” he said.
To reduce plastic pollution and microplastic levels in Africa, Idowu noted that “we need more
countries to ban single-use plastics. At the moment, about 10 countries are considering or already
have a partial ban on single-use plastics. The more countries that ban these, the better for the
Co-ordinated and comprehensive action is necessary across African countries, said Idowu, because
“we saw in Kenya for example, when they banned single-use carrier bags, and production was not
banned in neighbouring countries, then the bags were smuggled into Kenya. Now we’re finding
those bags back in the environment. We have to fight plastic pollution as a region, and not just as
individual country” said Idowu.