Following news that mosquitoes are ingesting microplastics comes word from researchers at Cardiff University that one in every two freshwater insects also contain harmful microplastics.

In what is the first U.K. study of river insects and microplastics, researchers looked at three different types of mayfly and caddis larvae and discovered that all of them had ingested plastic material regardless of how they feed.

Fred Windsor, Ph.D. student at Cardiff University, said: “Every year, between eight and twelve 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 that ingestion by insects is very likely.”

During their research, the team determined that while plastics were discovered in higher concentrations where wastewater fed into to the flow of the river, the plastics were also found upstream and downstream of sewage outfalls — a suggestion that microplastics are entering rivers from a number of different sources.

Professor Steve Ormerod, co-director of Cardiff University’s Water Research Institute added: “Urban rivers in the U.K. 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."

Professor Isabelle Durance, director of the Water Research Institute at Cardiff University, said: “Although people are more and more aware of the damage caused to ocean wildlife from ingesting plastics, the potential problem of plastics in river ecosystems has been seriously overlooked.

“The water industry, environmental regulators, the plastics and packaging industries, and ordinary people concerned about the environment see this as an increasing priority, and this study provides yet more evidence that we need a fuller assessment of the sources, movements and effects of microplastics as they are transported between the land and sea along rivers.”