"Polychlorinated biphenyls were once widely deployed as dielectric and coolant fluids in electrical apparatus, carbonless copy paper and in heat transfer fluids

"Polychlorinated biphenyls were once widely deployed as dielectric and coolant fluids in electrical apparatus, carbonless copy paper and in heat transfer fluids.[1] Because of their longevity, PCBs are still widely in use, even though their manufacture has declined drastically since the 1960s" Hydrophobic, highly soluble in organic solvents, oils & fats. How long ago were these pollutants (PCBs) deposited? A quick check shows toxicity was known and acted on in the 70s. [1] Is this a concentration by old pollution or is it still happening? The article seems to suggest both. A higher level article is here: https://news.ycombinator.com/item?id=13639274 https://news.ycombinator.com/item?id=13639274 Reference [0] https://en.wikipedia.org/wiki/Polychlorinated_biphenyl https://en.wikipedia.org/wiki/Polychlorinated_biphenyl