Killer whales under threat from persistent PCB chemicals

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Killer whales under threat from persistent PCB chemicals

Although PCBs (Polychlorinated Biphenyls) were phased out in the 1908s, their impacts on top predators, such as orcas, continue.  In this blog by Charlotte Coquard, she looks at current research into PCSs and their continued impact on our marine environment.

Charlotte argues that more needs to be done – including by the EU – to prevent ongoing PCB releases from building products and to ensure that all sources are dealt with.

PCBs are a group of chemicals which were produced in large quantities by companies and were widely used in electrical equipment, sealants and paints. Their production was phased out in the mid 1980’s in Europe, and they are now banned by the global Stockholm convention, as they were found to be toxic and to accumulate in wildlife and people. Despite these bans, releases of PCBs to the environment continue because they are present in building products and electrical equipment.

A study by The Institute for Zoology and the Zoological Society of London (ZSL) has been project looking at stranded cetaceans (whales and dolphins), and this revealed the scale of the problem. European waters are a “hot spot” for PCBs and although concentrations of PCBs in cetaceans started to decline after the EU ban, they have since stabilised at very high levels in striped dolphins, bottlenose dolphins and killer whales.

The scientists’ analysis was that the levels of PCBs in the cetaceans were high enough to cause reproductive declines and suppress population recovery.

They also noted that populations are declining. A small pod of killer whales has been monitored around North West Scotland and Western Ireland waters, for 19 years, but not a single calf has been seen. The pod is facing extinction; killer whale populations are also in serious decline around the rest of Europe.

A recent autopsy of a UK killer whale, found dead and entangled in fish lines, revealed that the whale had accumulated 950mg/kg of PCBs in its blubber – more than 100 times the 9mg/kg limit considered as safe.

The autopsy also indicated also that the old whale (around 20 years) had never produced a calf. The scientists suggest that it is possible that PCBs had affected the orcas’ brain, because killer whales are clever animals which are almost never found entangled in fish lines.

PCBs hardly break down and therefore persist for decades in the natural environment, travelling long distance and polluting the remotest places on earth such as the Artic or the deepest trenches of the ocean.

PCBs bioaccumulate in the food chain, building up in fatty tissues, with those animals at the top of the food chain (like killer whales and humans) the most contaminated.

These persistent properties mean that, although their use was phased out, they are still present in the environment