Author, Devra Davis' first chapter of her book, When Smoke Ran Like Water, discusses the history and investigations surrounding the Donora Fluoride Fog disaster of 1948.  This is one of the most significant air pollution events in U.S. history, and helped to spark the movement that eventually gave rise to the Clean Air Act.  This is also a case study for the impacts of a temperature inversion on air pollution buildup. The chapter can be downloaded as a .pdf file, and an accompanying worksheet of discussion questions is available for teachers to use.