Things like DDT and other persistent organic pollutants have been trending downward, in terms of worldwide residues, for years. Advanced nations have cleaned up emissions of many of these from manufacturing processes, or in the case of things like DDT, greatly reduced their use.
Now, though, there's a problem. Arctic ice melting. (With industry concentrated in the Northern Hemisphere, the problem is greater here than in the Antarctic.)
The melting Arctic ice, driven by global warming, is starting to release more and more stored quantities of these pollutants.
Especially since these pollutants concentrate at the top end of the food chain (which is why DDT was so harmful to bald eagles) environmentalists rightly note that this news is grim.
It's probably grimmest for polar bears, being both at the top of the food chain and threatened as a species due to diminution of ice floes.
Exactly how grim it is remains to be seen. Especially if we ask if an ever-industrializing, and dirtily-industrializing, China adds to the POPs even as less sea ice is around to temporarily absorb them.
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