In the early 1980's I had to complete a project in a production plant in LA. One day we were sitting in the cafeteria discussing the weather. I naively asked why it always seemed so cloudy if LA gets so little rain? Everyone laughed and told me it wasn't rain clouds but rather smog. The next comment someone made was how beautiful the mountains looked on a clear day. I was there the better part of a month before there was actually a "clear day". I was astonished to see the ring of mountains surrounding the city.
Flying back to Chicago I could smell diesel fumes about 100 miles from the city. I looked out the window and could see what looked like the cloud that always surrounds Pig Pen in the old Snoopy comics. It was the pollution hovering over the downtown area. The top of the Sears tower was barely peeking out of the mess. In less than 2 months I'd seen the 2 worst examples of pollution in my life.
Thankfully we've made some progress on air quality since then. I really wonder what we could accomplish without the politics and special interests.