Killer whales are at serious risk of extinction because of persistent environmental chemical pollution, researchers have warned.
A new study suggests that more than half of orca groups around the world are under threat, with those in the UK, the Strait of Gibralter, off Brazil, Japan and California all but doomed.
The main threat to killer whales comes from polychlorinated biphenyls, commonly referred to as PCBs, found in everything from plastics and paints, to electrical equipment.
Although banned 10 years ago, PCBs have amassed in the environment, leaching into the ocean.
Because killer whales are predators, PCBs absorbed by their prey, in particular affect the ovaries in female orcas, harming their abilities to produce calves, while also suppressing the imune system.
Paul Jepson, from the Zoological Society of London, says this group will "disappear in my lifetime".
"Over 50% of the populations that we've got data for will actually collapse in our model," he told the BBC's Science In Action programme.
"PCBs are such highly toxic chemicals, and they persist in the environment. And it's the killer whales that have by a long way the highest exposures now of any species on Earth; certainly any mammalian species."
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