Last updated November 8, 2018 at 4:16 pm
PCBs, chemicals that were banned across most of the globe over 30 years ago, are still wreaking havoc on orca populations today, according to international researchers.
Research published in Science today has found polychlorinated biphenyls, or PCBs, are negatively affecting killer whales’ immune systems and ability to reproduce.
In an Expert Reaction to the AusSMC, PhD Candidate Rebecca Wellard at Curtin University said the findings are “heartbreaking” because while killer whales once thrived in all oceans of the world, today they are at “a high risk of population collapse.”
PCBs are chemicals that were commonly used in electronics and industrial processes over 30 years ago.
The authors used available data on PCB effects and concentrations in killer whales to predict killer whale populations over the next century.
Associate Professor Susan Bengtson Nash from Griffith University said: “PCBs manufacture has been tightly regulated worldwide for more than a decade, yet the legacy of these chemicals remains a constant environmental threat for high trophic level consumers such as killer whales.”
The researchers expect reasonable population growth near less-contaminated waters like the Arctic and Antarctic, but near industrialised countries like the UK and Japan, killer whale populations are heading towards a complete collapse.
According to Dr Ian Musgrave at the University of Adelaide, killer whales are at a high risk of exposure to PCBs because they have “substantial fat deposits” and sit at the top of the food chain.
“PCB’s dissolve readily in fat and can accumulate in predators,” he said.
“This is particularly worrisome in animals such as killer whales which not only eat contaminated fish but other predators such as penguins and seals which have accumulated far more PCB’s than fish.”
Associate Professor Oliver Jones from RMIT said the paper “made depressing reading.”
“The work illustrates the unforeseen consequences, and sheer environmental persistence, of PCBs which look set to continue to cause significant problems in the future, over three decades after they were banned,” he said.
The paper’s findings suggest the current efforts to protect killer whales may not be enough to save them, especially since more than 80 per cent of global PCB stocks are yet to be destroyed.
This threat is in addition to the numerous other factors that threaten marine wildlife every day.
“10 million new chemical substances are produced every year for application in everything we consume and use.” Associate Professor Bengtson Nash said.
“As such, the effects of known harmful chemicals, such as PCBs, must be considered in the context of the cocktail of chemicals, humans and wildlife alike are exposed to daily, for which toxicity is yet to be properly evaluated.”
Dr Musgrave said the paper’s findings “must be taken very seriously.”
“Given the other environmental pressure that these animals are subject to, conserving killer whales may be harder than expected,” he said.