<p>The air isn’t that bad in Philly. The area had a grand total of 2 bad air days last year, 41 fewer than Bakersfield, CA, #2 on the list. (They were both in the summer, too, so largely irrelevant to Penn students unless they live here year-round.) The issue that put Philadelphia at the head of the list is the large number of Superfund sites in the larger SMSA, which includes huge chunks of southern New Jersey and Delaware, the original home of America’s chemical industry, as well as a bunch of old refineries and lots of brownfields sites in depopulated areas of the city. Smog isn’t a big concern.</p>