Air pollution is definitely a problem in Cairo, which is not surprising
since so many people (16 million? 20 million?) occupy a relatively small
area. The weather patterns seem to work to keep the smog collected in the
valley where the city is situated. From the surrounding high ground (the edge
of the desert) you can see that the city is in a large canyon carved by
the river Nile. October seems to have the worst air, apparently because
the rice fields are burned. On most recent mornings you can smell the smoke
in the air, and visibility is very restricted.
