For the first time, scientists have found evidence of plastic contamination in freshwater fish in the Amazon, revealing the extent of the plastic pollution problem the world faces.

In a study published in the journal Environmental Pollution, a team led by Marcelo Andrade from the Federal University of Pará in Brazil describe how they found plastic debris in a variety of fishes in Brazil’s Xingu River, a tributary of the Amazon River.

“Plastic bags, bottles, fishing gear, and other products are entering Amazonian water bodies and degrade into meso- and micro-plastic particles that may be ingested, either directly or indirectly via food chains, by fishes,” the team wrote.

Looking at the stomach contents of 172 specimens, they found pieces of plastic ranging in size from 1 to 15 millimeters in a quarter of them. And there was no consistent pattern – fish with different diets (omnivores, herbivores, and carnivores) were all found to have plastic in them.

In total, more than 80 percent of the species they examined had ingested plastic, with 96 pieces of plastic found in 46 fish. This included the red-bellied piranha and the redhook silver dollar. The dozen distinct polymers of plastic identified are used in the manufacturing of bags, bottles, and more.

“It was a sad surprise because in the initial stage of our research the main objective was to understand the feeding ecology of fish, but when we started analyzing the stomach contents we found plastic,” study co-author Tommaso Giarrizzo from the Federal University of Pará in Brazil told The Guardian. “It’s alarming because this pollution is spread throughout the Amazon basin.”

The research highlights the problem of plastic in environments like this, with rivers said to be the cause of up to a fifth of all ocean plastic waste. It shows that oceans are not the only places we should be worried about when it comes to the impacts of plastic pollution. About 60,000 tonnes (66,000 tons) of plastic are thought to be carried by the Amazon River into the Atlantic Ocean every year.

But the world is now starting to push back against plastic pollution. Some of the biggest brands on the planet recently pledged to eliminate single-use plastic from their products, while the EU has also voted to ban single-use plastics.

And that's pretty good timing, because we're starting to find plastic waste all over the place. Aside from this latest study, last month scientists also reported that microplastics had been found in human feces.