PCB

PCBs, polychlorinated biphenyls, are a class of 209 chlorinated congeners once manufactured as Aroclor and Kanechlor mixtures for transformers, capacitors, and hydraulic fluids. Production was banned in most countries by the late 1970s, and the Stockholm Convention lists them under Annex A (ban on production and use) with Annex C covering unintentional formation. They are persistent organic pollutants: lipophilic, bioaccumulative, and toxic, with dioxin-like congeners causing immune and reproductive harm. PCBs persist in marine sediment and biomagnify to apex predators, and remain the contaminant most linked to population decline in European killer whales.