London’s River Thames is full of secrets: home to human teeth, deadly Amazonian Piranha, and “hyperactive” eels prone to swimming through high concentrations of cocaine.

But are those somebody’s gnashers snarling from under Tower Bridge — or bottle caps? The Thames wears its most insidious horrors firmly on its sleeve. In fact, it’s impossible to miss.

Britain’s second-largest river has a vast plastic problem, documented by a new report from scientists that have noted that it’s among the most plastic polluted rivers in the whole world.

The study from researchers at Royal Holloway, University of London, found that in some places along the 346km river, 94,000 microplastics flow per second — “comparable to some of the highest recorded in the world.”

It examined material in two sites: Greenwich in southeast London and Putney in southwest. Common plastic culprits included fragments from large items like food packaging, glitter, and, despite a 2018 ban, microbeads from cosmetics products. 

Scientists also discovered plastic from sanitary pads and balloons inside crabs in the Thames, while wet wipes flushed down toilets across London — known to create fatbergs — frequently appeared along its shoreline, creating “reefs” of rubbish. 

And given the explosion in the manufacturing and consumption of personal protective equipment (PPE) to guard against COVID-19, the authors of the study have warned that the problem could be set to get even worse.

"Taken together these studies show how many different types of plastic, from microplastics in the water through to larger items of debris physically altering the foreshore, can potentially affect a wide range of organisms in the River Thames," said Professor Dave Morritt from Royal Holloway.

"The increased use of single-use plastic items, and the inappropriate disposal of such items, including masks and gloves, along with plastic-containing cleaning products, during the current COVID-19 pandemic, may well exacerbate this problem,” he added.

Deeply worrying to discover the horrific levels of plastic pollution in the river Thames! One of the most polluted in the world! Time for radical action to tackle plastic waste! @BBCr4today

— Barry Sheerman MP (@BarrySheerman) July 21, 2020

The density of the microplastics in the Thames was recorded at 19.5 plastics per cubic metre. While this is less than China’s Yangtze river — the longest river in Asia — it’s markedly more than the Chicago River in the US and the Rhine in Germany.

And it’s a problem not limited to the Thames either. Indeed, environmental nonprofit organisation Greenpeace found plastic in every single river they tested in the UK, while the River Mersey in north-west England had proportionally more plastic than the Great Pacific Garbage Patch — the most polluted patch of water on the planet, three times the size of France.

Now, researchers are urging the government to enforce stricter regulations on the disposal of plastic in order to protect the river’s wildlife — and asked the public to be more conscious about what they choose to throw away. There are 125 species of fish that live in the Thames, according to the London Wildlife Trust.

"Our study shows that stricter regulations are needed for the labelling and disposal of these products,” said Katherine McCoy, another co-author. “There is great scope to further research the impacts of microplastics and indeed microfibres on Thames organisms."

She added: "People can make much more of a difference than they might think.”