NEWS that microplastics are being ingested by aquatic insects in our rivers has increased concern about the likelihood of plastic entering the food chain and possibly being a health hazard to fish and ultimately humans.

Recent microplastics research, the first of its kind, was undertaken in rivers in South Wales by a team of scientists from Cardiff and Exeter Universities.

They found that at least half of all aquatic insects surveyed had ingested microplastics, defined as pieces of any type of plastic debris under 5 mm in length.

This was at all sites sampled and in all the three species of mayfly and caddis fly larvae studied, regardless of whether they lived in the water column or on the riverbed.

12 million tonnes of plastics

Lead author, Fred Windsor, said: “Every year, between eight and 12 million tonnes of plastics are thought to be entering the world’s oceans, but around four million tonnes of it passes along rivers.

“In some cases, there can be over half a million plastic fragments per square metre of river bed, so ingestion by insects is very likely.

“In our study, we sampled insects upstream and downstream from sewage treatment works on the River Taff, River Usk and the River Wye, and found plastics were surprisingly widespread.

“Although we found that microplastics occurred in higher concentrations where wastewater contributed more to river flow, we found them everywhere we looked.” the doctoral student at Cardiff University added.

The reports co-author, ecologist Steve Ormerod, of Cardiff University’s Water Research Institute, said: “Urban rivers in the UK have been recovering from decades of gross pollution, but growing information illustrates that plastics are a new risk for river organisms not just in towns and cities, but even in some rural areas.

“Problems could arise from the physical effects of microplastics, from their direct toxicity or from pollutants that they transport, and plastics in insects mean that animals using them as prey could also be affected.

“At present, however, our understanding of the risks to wildlife and people is absolutely rudimentary. We need to improve this situation urgently to know how best to manage the problems,” Professor Ormerod added.

80% of microplastics via run-off

Lauren Mattingley, science officer from the organisation Salmon and Trout Conservation, commented: “Around 80 per cent of marine microplastics come from freshwater run-off, meaning there is a whole period where microplastics persist in rivers before they are flushed into the ocean

“It is essential we stop seeing rivers simply as plastic ‘couriers’ and answer the big question: what impact are these plastic particles having on life in freshwater?

“Waste water treatment plants (a large input of microplastics that come from domestic and industrial sources) are currently not designed to remove microplastics effectively, but new filtration options are being discussed.

“New research is being commissioned and investigations are being made into understanding and controlling the freshwater element of plastic pollution.

“We are now partners in the first ever coordinated global microplastics river survey with the University of Birmingham called 100 Plastic Rivers and we will begin our sampling this year on Hampshire’s River Itchen,” Laura added.

Facts about microplastic pollution

  • Discarded plastic bags, bottles and cutlery, as well as surface water run-off containing abraded road paint and bits of automobile tires, are probably contributing to microplastic pollution all along the length of freshwater rivers.
  • Other culprits include city dust, personal care products and the washing of synthetic fabrics.
  • A single wash of one polyester fleece jacket can release 1,900 plastic fibres.
  • One study estimated that 28 per cent of all microplastic came from tyre wear.
  • An estimated 17 billion plastic particles were flushed into the sea from a river catchment area in Manchester in one winter.
  • 80 per cent of marine microplastics come from freshwater run-off.
  • 83 per cent of water samples from major metropolitan areas around the world contained micoplastic.
  • A high proportion of bottled water also contains microplastic.

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