by Ben Webster
A third of fish in the Thames Estuary and Firth of Clyde have eaten plastic, a study indicates.
Nylon and polyester from clothing, wet wipes and fishing nets were the most common types of plastic found in their guts.
Scientists from the Natural History Museum trawled both rivers and examined almost 900 fish. They discovered that 28 per cent of the fish in the Thames and 39 per cent in the Clyde in Scotland had ingested plastic.
Whiting, flounder, dab, pouting, lesser-spotted dogfish and shrimp were among the species affected, and they had an average of three and up to 23 tiny pieces of plastic inside them.
The scientists said that many of the pieces of plastic were fibres that had probably come from sewage works in the Thames Estuary. Each item of synthetic clothing can shed thousands of plastic fibres per wash, and many waste water treatment plants do not have filters small enough to remove them.
The study, published in Marine Pollution Bulletin, said that fibres could also make their way into the river from sewage sludge deposited on agricultural land and washed into waterways during heavy rain.
Alexandra McGoran, one of the authors, said that the plastic could harm the fish by causing abrasions and also via the chemicals on the fibres, which can act as carcinogens and hormone disruptors.
She said that the plastic was unlikely to have a fatal impact, but could affect the growth of fish and their ability to reproduce because of the extra energy demands on their immune and cell repair systems.
She added: “People have started to really take note of the severity of plastic pollution and our research further demonstrates why this is such a pressing issue. Both rivers are extremely diverse ecosystems, home to hundreds of different species. To see this large number of species that our plastic waste is putting in danger is actually rather shocking.
“Our results show the need for more research into freshwater and estuarine ecosystems to be carried out so we can better understand the effects microplastics are having on their inhabitants.”
Ms McGoran said that wet wipes flushed down toilets could be a source of some of the fibres. These could be deposited in rivers via sewer overflow pipes. More than 5,000 wet wipes were collected from a short stretch of the Thames foreshore during a litter-picking event earlier this year.
She said that people could reduce the risk to fish by not flushing any wet wipes down lavatories, including those that are labelled “flushable”. She pointed out: “Flushable does not mean biodegradable. Flushing anything down the toilet other than human waste and toilet paper increases the chances of microplastics in the water system.”
Paul Clark, a co-author, said: “What I find most depressing about plastic pollution of our aquatic environment is that it is now irreversible and its presence will persist for many generations.
“Assuming current trends continue, the total amount of plastic produced by 2050 will be 33 billion tonnes. Plastic pollution is on the same calamitous magnitude as climate change and deforestation. We are in need of a monumental behavioural change in human attitudes.”