Pollution
Because of human activity the oceans are getting more and more polluted. At a lot of places mercury (Hg) is used in the process of mining for gold and it finally ends up in the ocean. Cadmium (Cd) is used in a lot of processes as well and is found in the ocean water as well. The heavy metals are absorbed by marine life and finally found in the animal at the top of the food chain. One of those species is the pilot whale.
The toxic metals are finally found in a lot of organs, even in the brain. These high levels of toxics lead to toxic stress in the long-lived marine mammals, because the concentrations increasing with age.
Photo: periodictable.com