Maybe it was too good to be true. When substances like PCBs and DDT were largely banned in the 1970's we witnessed a steep decline in their occurrence in our environment. A very real and very simple success story. But the story isn't over. The major concern with this class of pollutants is that they simply don't break down in the environment. In turns out that back when we were pumping volumes of this rubbish into our environment plenty of it was captured in glaciers. And as glaciers around the world retreat in the face of global warming these persistent nasties are being re-released into our environment.
More details here.