The River Thames in London. Ullswater in the UK’s Lake District. Loch Lomond in Scotland. What do they have in common? According to a new study, this: they all have been contaminated by microplastics, which have permeated water sources across the planet from the surface of rivers right down to the depths of the oceans.

A team of researchers from Bangor University in Wales and the nonprofit Friends of the Earth examined 10 water sources around the United Kingdom and found that microplastics have polluted all of them. Using a fluorescence lighting system, they identified and counted tiny plastics of less than 5mm in size in every liter of water they collected.

They found that microplastic pollution levels range from more than a 1,000 pieces of plastic per liter in the river Tame in Greater Manchester to 2.4 pieces per liter in Loch Lomond in Scotland. “It was startling. I wasn’t expecting to find as much as we did,” said Christian Dunn, an expert at Bangor University who led the research. “It is quite depressing they were there in some of our country’s most iconic locations,” he added.

“Microplastics are being found absolutely everywhere [but] we do not know the dangers they could be posing,” Dunn went on. “It’s no use looking back in 20 years time and saying: ‘If only we’d realised just how bad it was.’ We need to be monitoring our waters now and we need to think, as a country and a world, how we can be reducing our reliance on plastic.”

Microplastics, such as microbeads used in cosmetics, pose grave risks to marine animals, many of which either mistake them for food or, like whales, accidentally swallow large quantities of them. Worse: the sand grain-size plastics, scientists say, act like magnets for pollutants in water as these pollutants attach themselves to microbeads and can pass into the fish that feed on them. That way they enter the food chain and we often end up digesting them ourselves to the effect that microplastics can start accumulating in our own guts.

“Plastic is polluting our rivers, lakes and wetlands in a similar way as pollutants such as so-called ’emerging contaminants’ like pharmaceutical waste, personal care products and pesticides,” Dunn says. “[I]t’s now clear that microplastics should be considered a serious emerging contaminant and there needs to be a concerted effort to regularly monitor all our inland waters for them.”