Toxins that were banned years ago are still threatening ocean mammals, say scientists.
Polychlorinated biphenyls, commonly known as PCBs, may be slowly wiping out killer whale populations worldwide, reported Science.
“It’s sobering to be made aware of the potential long-term effects of chemicals that were introduced into the environment over 80 years ago,” says Steven Bursian, an environmental toxicologist at Michigan State University in East Lansing, in an interview with the magazine. “It’s a wake-up call that similar predictions could be made about several other species.”
PCBs were first discovered in coal tar in the late 1800s and subsequently used in a variety of functions from hydraulic fluids to lubricating oils, paint and concrete stabilizers, and nonflammable insulation in electrical transformers, before scientists ultimately linked them to cancer immune system, reproductive, and endocrine related health problems in both people and animals, noted the report.
The US banned their production in 1978, followed by a worldwide ban in 2004. But the pollutants don’t break down easily, say scientists.
“The PCB story is not over,” Jean-Pierre Desforges, an ecotoxicologist at Aarhus University in Denmark and author of the study told Science.
Having teamed up with modelers Ailsa Hall and Bernie McConnell from the University of St. Andrews in the United Kingdom to estimate the toll of the PCBs, the group built on lab studies in which Desforges showed that PCBs extracted from whale blubber affect killer whale immune function.
Concurrent studies on mice estimated the PCB levels that raise susceptibility to disease and impair fertility, as well.
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Based on the lab results and on year-by-year PCB concentrations in individual killer whales, the team has concluded that of the 19 populations studied, more than half will decline because of PCBs’ effects, noted the report.
Chemicals like PCBs are taken in by plankton at the base of the food chain, then eaten by herring and other small fish, which are in turn eaten by even larger fish, noted the New York Times. With each transference, PCBs become more and more concentrated, making the most at-risk killer whales those that eat seals and other animals that are already fairly high on the food chain and deeply contaminated.
Other top predators, such as sharks and dolphins, likely have dangerously high PCB levels as well. Meanwhile, tumors and increased disease in sea lions seem linked to high PCB levels, noted the report.