It's stunning to look at pictures of American cities before we got serious about curbing air pollution. A heightened environmentally sensibility and the Clean Air Act has made a big difference in the quality of the air we breathe.
Then again, it only takes a wildfire or two to bring the smoke rolling into our communities today. And other parts of the world face air pollution on a daily basis.
Beth Gardiner gives us a world tour in the book Choked: Life and Breath in the Age of Air Pollution.
The author talks about clean air and global attitudes toward it.