Polychlorinated biphenyls, PCBs—once used in coolants, concrete, paint, light bulbs, and electrical capacitors—are persistent compounds that, having entered the ocean through stormwater and waste, can take many decades to break down into benign molecules. Though these substances were phased out by governments in the 1970s and ’80s, PCBs have remained durable in the ecosystem. One site where they have intensified is within the bodies of killer whales––iconic, black-and-white whales, apex predators also known as orca. Research models released in 2018 foretold that all killer whale populations
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