That picture might even have been taken during the impressive sand storm over Beijing in April this year [2], that's the most foggy day I've seen in the last 12 months here. Looking at the sand storm coming and swallowing the buildings from our offices on 10th floor was quite impressive. :-)
Also, if you live in a big city on any continent, you might want to check your own pollution levels using the AQI site [3], you might be surprised by the results. ;-)
[1] https://www.youtube.com/watch?v=lp7nLlaLaBg
[2] http://www.huffingtonpost.com/2015/04/16/beijing-sandstorm_n...