You’d think that some place as deep as the Mariana Trench, 26,000 to 36,000 feet under the surface, would still be untouched by humanity. A recent study published by Nature Ecology & Evolution, however, shows that these extensive ecosystems are bustling in deadly chemicals, mnn.com announced.

Led by Alan Jamieson of Newcastle University in England, a crew of researchers set out a remote controlled vehicle with bait traps into the trench at 30,000 feet under sea level, theguardian.com reports. They then caught many small crustaceans called amphipods and found out that these creatures contained way more toxins than other sea life living in some of the most polluted oceans.

“In fact, the amphipods we sampled contained levels of contamination similar to that found in Suruga Bay, one of the most polluted industrial zones of the northwest Pacific. What we don’t yet know is what this means for the wider ecosystem and understanding that will be the next major challenge.” Jamieson said in a statement for mnn.com.

According to theguardian.com, the toxins they found in the creatures included polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs). These chemicals were used for four decades until they got banned in 1970. Some of these chemicals got dumped into the ocean, and never decomposed as it is resistant to natural degradation.

Another theory that scientists have is that the pollution is a result of deep sea creatures consuming contaminated carcasses of animals and plastic debris, reported mnn.com. “The fact that we found such extraordinary levels of these pollutants in one of the most remote and inaccessible habitats on Earth really brings home the long-term, devastating impact that mankind is having on the planet,” Jamieson explained. “It’s not a great legacy that we’re leaving behind.”