It was like something out of a horror movie. But it really happened. Almost 60 years ago, a fog descended upon the small industrial town of Donora, Pennsylvania. The fog would cover the town over the next four days, killing 20 residents and hospitalizing 7,000 - half the town's population. In 1948, the residents of Donora were accustomed to the smoke and smell from the US Steel Corp's zinc works and steel plants. They accepted the pollution as a fact of life and the cost of employment. But when an inversion set in, trapping the town's air in the narrow river […]