This glorious picture of the sunset by Eschipul in Houston reveals a sky flooded with ozone, a form of airborne pollution. In fact, the American Lung Association just ranked Houston number 5 for ozone pollution in its annual list of most polluted cities. Pollution makes sunsets extra-beautiful, as you can see in the two other sunsets (below) from more "winners" on the ALA's list.
Baton Rouge, which you can see here, glows in the particulate matter of its pollution. Dentalben took this photo. It's the tenth most ozone-ridden city in the U.S.
And it should be no surprise to anyone that Los Angeles is the most polluted with ozone. Here is a beautiful view of LA, showing off the dreamy, weird layer of gunk that hovers in a brown band over the city. Steven Buss took this photo.
Most Polluted Cities [American Lung Association]