Killer whales are at risk of extinction off industrialized regions of Europe from poisonous chemicals banned decades ago that are still leaching into the seas, scientists said on Thursday.
The study, which took samples from 1,000 killer whales, dolphins and porpoises, urged tougher rules for disposal of toxic man-made PCBs (polychlorinated biphenyl) that were used in paints, electrical equipment and construction until the 1980s.
"It's really looking bleak … We think there is a very high extinction risk for killer whales as a species in industrialized regions of Europe," lead author Paul Jepson of the Zoological Society of London, told a telephone news conference.
The study, by scientists in Spain, Ireland, Portugal, Slovenia and Britain, said concentrations of PCBs in the blubber of killer whales off Europe, as well as in striped dolphins and bottlenose dolphins, were among the highest recorded worldwide.
Levels were lower in harbor porpoises, the fourth species covered by the study in the journal Scientific Reports.
Washed into rivers from unsealed storage sites, PCBs contaminate the seabed where they are eaten by creatures such as mussels or crabs that in turn get consumed by fish that are food for long-lived predators such as killer whales.
PCBs lodge in fat and build up in the blubber of marine mammals. Killer whales, which are black and white, grow to 10 meters long (33 ft) and can live up to 100 years. PCBs can also be passed on to the young in their mothers' milk.
Killer whales thrive in many parts of the world, from the Arctic to Antarctica, that are further away from sources of pollution.
Without much stronger restrictions, "PCBs will continue to drive population declines or suppress population recovery in Europe for many decades to come," the experts wrote.
Levels of PCBs in killer whales off the United States are lower than in Europe, perhaps because Washington banned PCBs in 1979 while Europe lagged, banning them in countries bordering the Mediterranean only in 1987.
The study sampled killer whale populations off the Strait of Gibraltar, Spain's Canary Islands, Britain and Ireland. Previous European populations have vanished from industrial regions from the North Sea to the Mediterranean.
