An astonishing new report out of the UK shows something that scientists weren’t expecting to see: chemicals, banned back in the 1970s, have been found in the deepest parts of the Pacific Ocean. It surprised scientists to see such high concentrations of pollutants such as PCBs and PBDEs so far down in the furthest reaches of the oceans, according to the study, which was published in the journal Nature Ecology and Evolution.

A team at the University of Newcastle traveled to the Mariana and Kermadec trenches, two of the deepest spots in the world, and sampled pollutants in the fatty tisuse of a certain type of crustacean that lives in the ocean depths. They found that pollutants on the amphipods, chemicals that had been banned since the 20th century that were used as insulators and flame retardants, were in surprisingly abundant supply, according to a university statement.

These chemicals were likely released through industrial accidents, or discharges from landfills. And the fact that they could be found so deep in the ocean so many years later shows why they were banned, as they are highly resistant to breaking down naturally.