I was in Homestead Pa. this week and parked my truck behind these stacks that are left as a monument to the Carnegie steel mills that were once there. The whole area where the mill once was has been transformed into a shopping area. What was once production has become consumption. People I spoke with said that the air quality during the mills heyday was very bad. Here is a link for more about the history of Homestead. http://en.wikipedia.org/wiki/Homestead,_Pennsylvania