Banned PCBs threat to killer whale survival
COPENHAGEN: Killer whale populations may be facing a complete collapse due to pollution from a nowbanned chemical, according to a study published in the journal Science yesterday.
Polychlorinated biphenyl (PCB), a highly toxic and carcinogenic chemical, is being found in high concentrations in killer whales, the study says.
The chemical harms their immune systems and ability to reproduce.
PCBs were used in electrical appliances, paints and other products but were banned worldwide more than three decades ago.
However, they are still available in parts of the world and they persist in the environment because they break down slowly.
The researchers said the chemicals had been found to concentrate in the blubber of whales and more than half of the world’s killer whales, or orcas, were affected.
They feared killer whale populations near industrialised regions were at high risk of population collapse over the next 100 years.
‘‘We knew that the PCB levels were high but it was really quite startling when we ran the num bers,’’ lead researcher JeanPierre Desforges, from Denmark’s Aarhus University, said.
‘‘Over 50% of those populations either had zero growth or they had considerable population decline, and for the worst cases a complete collapse.’’
Rebecca Wellard, a PhD scholar studying orcas and ecology at Curtin University in Australia, said killer whales sat at the top of the food chain, meaning they were more susceptible to pollutants in the ocean.
‘‘What makes PCBs unique from other toxins is that its molecules are extremely fatsoluble, meaning they accumulate easily in fats.
‘‘Unfortunately, once these PCBs are in the orca, the toxins don’t go away.’’
In 2016, a killer whale, nicknamed Lulu was found dead off the coast of Scotland with one one of the highest levels of PCB contamination ever found in an animal.
Scientists said last year 20yearold Lulu had never reproduced, even though most female killer whales reach breeding age at about 10.
Desforges said Britain’s killer whale population was showing significant signs of decline, and there had been no calves for more than a decade.