It has been getting ever harder to pretend that Antarctica is a pristine place. We like to think of it as being scoured clean by hostile winds and extreme cold. But more and more, Antarctica, like the Arctic, shows the lasting scars of human negligence. The effects of climate change are being felt far more strongly at the poles than elsewhere on the planet. Some of the most persistent and dangerous chemicals ever created have accumulated there and remain there. Take DDT, the long-banned pesticide. When it was still sprayed on crops and gardens across the globe, it moved through the atmosphere to the polar regions, where it was deposited in water, snow and ice, ultimately making its way into the food chain. The residue of DDT found in many Arctic species has declined in the past 30 years. But recently, scientists in Antarctica reported that Ad