There are many sources of chemical pollution in the marine environment such as; industrial and operational discharges, domestic sewage and run-off, atmospheric fallout, spills at sea, mining discharges and agricultural runoff. Of most concern are organochlorine pesticides like DDT and dieldrin and industrial chemicals like polychlorinated biphenyls (PCB’s).
PCB’s were manufactured from the 1920’s, but banned in the UK in 1981, and the rest of the EU in 1987. However, once these pollutants have entered the marine environment there is practically nothing that can be done to remove them. Resistant to biodegradation and very persistent in the environment so despite the ban, biomagnification in marine food webs continues to cause severe impacts among top predators such as cetaceans. These pollutants have a high affinity for lipids so bioaccumulate particularly in organisms with thick blubber layers such as cetaceans, causing a range of impacts from direct physical poisoning to degradation of important habitats.