By Dr. Becker
Polychlorinated biphenyls (PCBs) have left a toxic lasting legacy worldwide, even though manufacture was banned in the U.S. in 1979. The man-made chemicals were valued because they were not flammable and had both high chemical stability and boiling point, making them useful for electrical insulation and use in paints, plastics, dyes and for many other industrial purposes.
Sadly, the chemicals’ steadfastness is also one of their major downfalls, as they do not degrade in the environment and are still wreaking environmental havoc decades after their production has ceased. Worse, stockpiles of the chemicals still exist at waste storage sites, from which they may continually leach into the surrounding environment, including waterways.
UK Killer Whale Died With Extremely High Levels of PCBs
In 2016, a 20-year-old killer whale died in Scotland after becoming tangled in fishing ropes. An analysis revealed the whale, named Lulu, also had one of the highest levels of PCBs ever recorded in a marine mammal — 950 milligrams per kilogram (mg/kg). Damage is known to occur at 9 mg/kg, and the average killer whale in the northeast Atlantic is said to have PCB levels of about 150 mg/kg.1
In addition to causing cancer and adverse effects to the immune system, PCBs are endocrine-disrupting chemicals capable of harming the reproductive system. The analysis revealed that Lulu had never had a calf, and the pod that Lulu was part of — the last resident pod in the U.K. — has not had a calf in nearly 20 years.2 PCBs, which are known to cause infertility, are likely to blame.
Large, long-lived marine mammals like killer whales and dolphins are particularly at risk from PCB pollution. As predators at the top of the food chain, they eat animals already contaminated with PCBs, which continue to accumulate in their bodies as they grow older.
UK Orca Pod Likely to Go Extinct
Without new calves being produced, experts predict the resident killer whale pod will likely go extinct. Paul Jepson, Ph.D., of the Zoological Society of London (ZSL) led a study looking into how PCB pollution is affecting populations of killer whales and other dolphins.3 He told The Guardian, “This group will go extinct unfortunately … Without further measures, these chemicals will continue to suppress populations of orcas and other dolphin species for many decades to come.”4
Other animals at risk include those living in what the researchers referred to as “global PCB hotspots,” including the western Mediterranean Sea and southwest Iberian Peninsula. Jepson believes the absence of great white sharks in U.K. waters may also be related to the prevalence of PCBs.5 They wrote in the journal Scientific Reports that many marine mammals living in European waters are at risk:6
“Blubber PCB concentrations initially declined following a mid-1980s EU ban, but have since stabilized in UK harbor porpoises and SDs [striped dolphins] in the western Mediterranean Sea. Some small or declining populations of BNDs [bottlenose dolphins] and KWs [killer whales] in the NE Atlantic were associated with low recruitment, consistent with PCB-induced reproductive toxicity.
Despite regulations and mitigation measures to reduce PCB pollution, their biomagnification in marine food webs continues to cause severe impacts among cetacean top predators in European seas.”
Adding to the complex problem, PCBs dissolve easily in fat, including the high-fat milk whales and dolphins (as well as polar bears) produce for their calves. Female killer whales and dolphins may transfer up to 80 percent of their PCB load to their calves via their milk.7
Is There Hope for Marine Mammals?
PCBs can be destroyed using special high-temperature incinerators or attempted to be securely contained (and kept away from water supplies). Unfortunately, an estimated 40 million tons of PCBs still remain in circulation and more may be released as old industrial buildings are destroyed. Cleanup efforts have been estimated at up to $70 billion, but such efforts in the U.S. Hudson River area show remediation is possible.
The Hudson River was contaminated by PCBs by General Electric (GE) manufacturing plants. From 2009 to 2015, dredging of PCB-contaminated sediment (paid for by GE) was done on a section of the river and habitat reconstruction occurred to help restore aquatic plants to the area.8 Jepson believes similar efforts may help to restore marine mammals in Europe. Sharing his optimism with The Guardian, he explained:9
“We urgently need a similar approach in Europe … It’s been done mainly to protect human health, but there’s a wonderful [side effect.] A lot of wildlife is now slowly coming back including seals, seabirds and [bottlenose] dolphins and harbor porpoises. On both the east and west coasts, the great white is also recovering. Only killer whales are still doing badly but if the U.S. carries on the way it has been doing, then I think killer whales will make a recovery as well.”