The next photo shows what the grey winter does. Notice how the farthest building on the horizon seems to have disappeared.
And this orange-looking effect was not added by computers. That's what the sky does when we have a sandstorm.
I use the last building I can see as my smog-o-meter every morning. On especially clear days I can see the blue and white colors of some of the window frames. On moderately smoggy days, I can make out the silhouette of the building, but not see window colors. And on bad, "blurry" days, that building just isn't to be seen. Google Earth shows that building to be 3/4 mile away, or just over one kilometer.