At least half of the world’s killer whales are doomed to die from persistent ocean pollution, according to new research.
A long-banned industrial pollutant is still causing major damage to killer whales worldwide. Polychlorinated biphenyls (PCBs) were first discovered in coal tar in the late 1800s, and they began to be mass-produced in the 1930s. PCBs can form thick liquids that were used as lubricating oils, paint stabilisers and hydraulic fluids, among other things.
Before scientists linked the chemicals to cancer as well as immune, reproductive and endocrine problems in humans and animals, 1m tonnes of PCBs had been produced. The US banned their production in 1978, while a global ban came into force in 2004.
PCBs are still a problem
A group of scientists from institutions including Aarhus University, St Andrews University and Ocean Wise Conservation Association in Vancouver has found that the chemicals are still leaking into oceans around the world, and published the research in the journal Science.
The chemicals are affecting killer whales as the substances become concentrated up the food chain. The whales then pass on high doses to their young through their milk.
PCBs are still leaking into the environment from landfills, sediment at the bottom of rivers and other dumping areas. Microbes consume the chemicals, and the PCBs then build up in the fat of top predators, such as killer whales.
Scientists examined PCB contamination in 351 killer whales, analysing population prospects for the creatures around the world. They found that the pods living close to the shores of industrialised nations could be gone in as little as 30 to 50 years.
They then took existing data on how PCBs affect calf survival and immune systems in whales to model predictions for the animals. “Populations of Japan, Brazil, north-east Pacific, Strait of Gibraltar and the United Kingdom are all tending toward complete collapse,” the team said.
Predators vulnerable to contaminants
Killer whale pods in Brazil, the North Sea off the UK and around the Straits of Gibraltar are the most vulnerable because their PCB levels are highest.
According to the study, PCBs are far from the only pollutant present in killer whales. There is a long list of additional known and as yet unmeasured contaminants present. Growing underwater noise pollution and loss of key prey such as tuna to overfishing are further problems facing the animals.
The study warned that other predators, such as sharks and dolphins, likely have perilous levels of PCBs in their systems. In sea lions, increased disease and tumours seem to be connected to high levels of PCBs.
Dr Jean-Pierre Desforges, an ecotoxicologist at Aarhus University, said: “The PCB story is not over.”