MANCHESTER – New research suggests the amount of microplastics polluting the world’s oceans could be much greater than thought. A UK study uncovered the highest microplastic pollution ever recorded in a river close to Manchester in the North West of England.
Scientists tested river sediments at 40 sites across Greater Manchester and found that microplastics in abundance at each of of the sites. The researchers from the University of Manchester also showed that major floods in the North West in 2015-16 flushed more than 40 billion pieces of microplastic into the sea.
Such a huge surge in the amount of microplastics from one river catchment in a single event led the scientists – whose findings are published in Nature Geoscience – to conclude that current estimates for the number of microplastic particles in the world’s oceans is greatly understated.
Microfibres which emanate from clothing are the most abundant form of microplastic material found in the ocean, with some studies suggesting they may constitute up to 85 per cent. When items of clothing are placed in a washing machine, thousands fibres are shed and travel through sewerage and storm water and end up in the environment, in rivers and the sea.
Microplastics include broken-down plastic waste, synthetic fibres and beads from personal hygiene products. Microplastics harm marine life, which mistake them for food, and they can also ultimately be consumed by humans via the food chain.
In the Manchester University study, researchers analysed sediments in ten rivers in a 20km of Manchester with 39 of 40 sites showing evidence of microplastic contamination. After the winter floods of 2015-16, they took new samples and found 70 per cent of the microplastics had been swept away, a total of 43 billion particles or 850kg. Notably, they estimate that of those, around 17 billion would float in sea water, a finding which leads them to believe there may be far more microplastics in the oceans than previous studies have estimated.
The researchers said that in the worse hotspot, the River Tame, they found more than 500,000 microplastic particles per square metre in the top 10cm of river bed – the worst concentration ever reported and 50 per cent more than the previous record. But the researchers believe there may well be worse places in the UK – and indeed globally – where microplastic pollution is even more concentrated. “We don’t have much data for huge rivers in the global south, which may have so much more plastic in,” says the report.