When you typically stand outside your home do you smell spring flowers, maybe mulch? Does it smell fresh? Maybe you live near the ocean, and feel a lift in your soul from the fresh breezes off the ocean? Maybe you like hiking in the mountains where the air is fresh and fills your soul with lightness and joy?
Wherever you call home, you might be interested to see definite numbers regarding air quality showing where the air is fresh. Each year the American Lung Association compiles wonderful lists of the so-called Cleanest Cities, divided into ozone and particle criteria. It's an amazing site where you can actually "compare your air" if you live in the United States with that of other cities in America.
Not surprisingly, the seaboard states of the East Coast didn't pass many tests on the list, although there are many, many places in my home state of New Jersey, either on the Jersey Shore or in the bucolic western area of the state that would have. New Jersey itself was divided in half and combined with huge populations in New York/New Jersey and New Jersey/Camden/Reading in another, and contributes to the sense of New Jersey as an area with generally poor air quality. A close search of specific municipalities within New Jersey would likely prove to show very different results because, as we all know, industrial sites in New Jersey are generally centered around historic cities.
California, too, didn't pass many levels on the list either, despite the long ocean coastline and mountains in the east of the state. The northern part of the state had passable air readings in general, but the pockets of industry around cities generally correspond with failing ozone and particle pollution.
It's only common sense. If you want better air quality, better stay away from heavy industry of any kind.