National Public Radio: In Cairo, this is the season of the Black Cloud — the inky haze of pollution that on its worst days descends on the Egyptian capital with noxious, throat-burning fumes. The black cloud, a decade-old phenomenon, has been attributed to farmers burning rice straw after their harvest. But studies show there are several contributors to the foul air, and while the government has made some progress reducing the smog level, it has a long way to go. October and November are wonderful …