The extensive use of PCBs has left Killer Whales with an uncertain future. Is this a problem humanity can fix?

Source: WikimediaSource: Wikimedia

In 2017, a killer whale (oscines orca) named Lulu became tangled in fishing lines and washed up dead on the shores of Scotland’s Isle of Tiree. Her death reiterated the threat of fishing activity to marine life but also revealed a far more permanent issue that has no clear solution.

Lulu’s body was found to contain 957 parts per million (ppm) of polychlorinated biphenyls (PCBs), a group of man-made chemicals widely used in industry until the 1970s when a series of bans around the world prevented their use in new products. The bans were placed as evidence mounted that PCBs are potential human carcinogens and can cause a plethora of health issues in humans and animals alike. Their temperature and pressure resistance, stability and insulating properties meant they were widely used as dielectric, coolant and heat transfer fluid. However, the application of a PCB depends on its chemical and physical properties as these characteristics vary with chemical composition.

Decades of reckless disposal of products containing PCBs has released vast quantities of the chemicals into the oceans, the land and the air we breathe. PCBs do not easily break down and so can cycle between the water, air and land for very long periods of time. Since the ban, the level of PCBs in the environment has been declining, but only very slowly. As a result of their persistence in the ocean, a lot of PCBs are absorbed by plankton and so enter the oceanic food chain. They are then passed up the food chain and bioaccumulate in the top predator, hence why Lulu was exposed to such a high quantity of the chemicals. The high level of PCBs in Lulu’s body is deeply troubling for conservationists. Head of the Scottish Marine Animal Stranding Scheme, Dr Andrew Brownlow, said it was “20 times higher than the safe level that we would expect for cetaceans to be able to manage”. If Lulu had high levels of PCB in her body, it stands to reason that other killer whales and marine life do too. Such high values cause many worrying effects and can kill an organism outright.

Jean-Pierre Desforges of Aarhus University and Alisa Hall of the University of St. Andrews have found that high exposure to PCB decreases fertility. Their study was carried out upon minks as, for obvious reasons, running a controlled scientific experiment on killer whales is difficult. However, as both are aquatic mammals, the results are likely to be valid; in fact, this hypothesis was corroborated by an examination of Lulu’s ovaries that revealed she was no longer capable of reproduction. Should an orca remain fertile, the mother passes PCBs onto her calf during pregnancy and the chemicals dissolve into the mother’s milk. Therefore, calves are exposed to high doses of PCB at a very young age. With the chemicals being more toxic to calves than to adults, the calves suffer a much-increased risk of death in infancy and of being unable to reproduce if they live to adulthood. Entanglements of killer whales in fishing lines are very rare, so the nature of Lulu’s death has sparked speculation that PCBs also damage the brain, causing reduced cognitive ability. As Dr Brownlow points out, “killer whales are incredibly intelligent… [it is] plausible that there was [an] effect of the PCBs in some way debilitating her, so she wasn’t strong enough or even aware enough to deal with this entanglement”.

These impacts alone have dire implications for killer whales, particularly for the UK’s only orca pod: Lulu’s “West Coast Community” near Scotland. Following the passing of Lulu, there are only eight orcas remaining and no calf has been born for over twenty years. Members of the pod are likely to have similar levels of PCB to Lulu as British waters are highly contaminated from the significant use, and poor disposal, of PCB products in Western Europe. This means that if fears of reduced fertility are true, it is unlikely that the pod will ever have a calf again.

Few orca pods around the world are in such dire straits. But with PCB levels in the ocean remaining stubbornly high, many other pods could soon find themselves in the same situation as the West Coast Community. Humans created this problem, but humans will struggle to solve it. PCBs are nightmarishly persistent and will remain in ecosystems around the world until they degrade unless they are removed first. The US Environmental Protection Agency is attempting this in highly contaminated locations like the Hudson River by dredging PCB-contaminated sediment. This is very expensive due to energy required and the habitat reconstruction that must follow. Moreover, contamination of the oceans cannot be reduced this way as widespread ocean dredging would be impossible. PCBs can be removed from water using activated carbon filters which is effective in small scale applications like drinking water filters, but there is no straightforward way of filtering the oceans. There are signs of hope for the removal of PCBs from the environment, but technology must develop for this to be possible. A global effort is required for success but apart from in the USA, there is a startling lack of urgency.

Meanwhile, PCBs from pre-1970 products are still leaking into the land and oceans, slowing the rate of decline of the level of PCB in the environment. This means for the foreseeable future, the chemicals will bioaccumulate in orcas, increasing the risk of health issues and reducing fertility. The survival of each pod, and ultimately the entire species is contingent upon the degradation rate exceeding the rate of bioaccumulation. If this is not the case, then impotence will prevent successful reproduction and the entire species will face the same fate as the West Coast Community.

Lulu warned the world of the fate awaiting killer whales. Ignoring her message would not only be foolish, but shameful.