The wives of Swedish fishermen were passing PCBs onto their children before they were born, and through breast milk afterwards. The mainstay of their diet - fish from the Baltic. But we see an effect on the birth weight, indicating that something was going on. The health damage done by PCBs is decreasing, now that PCBs have been banned and cleaned up. Yet the Baltic still has PCBs and other POPs coming from other sources.
POPs are a global problem, requiring a global solution.
DDT, was used for years as a pesticide. Often sprayed from the air, DDT was a hammer to crack a nut - it's very toxic and very long lasting. It's also good at killing the mosquitoes that carry malaria. In Brazil, DDT used to be used with impunity to control pests on crops or mosquitoes that endanger health. Because the Amazon region is very peculiar, first, the population is very dispersed.