Poisons from plastics and electrical goods can take years to break down and disappear.
But they are carried along in water for hundreds of kilometres. Eventually they seep into food and water eaten by smaller animals and fish.
Inuit Eskimo communities are eating the food too, which could seriously damage them.
Most countries have now banned the use of these chemicals in their plastics. But some - like Russia and the US - still use some dangerous chemicals.
Now the World Wildlife Fund (WWF) want them to agree to stop using them.