The Walrus occupies the highest level in their food chain a long with Polar Bears.

The Walrus is at the top of this Arctic Marine Food Chain.

The Walrus eats Mullosks such as Whelks, Limpets, Sea Slugs, Mussels, Scallops, and Octopi.

And these creatures eat tiny drifting plants and animals (phitoplankton)  such as plankton and algae.

What do these food chains have to do with us? Well, we eat these things too. Some people eat walrus and since it is at a high level in the food chain it does get some contaminants so it is very likely that we could get those too.