Dense, acrid smog choked Cairo for the second day in a row yesterday, causing respiratory problems, sore throats, acute headaches, and flu-like symptoms for many of the city’s 16 million residents. Severe smog problems have plagued the city for several weeks in October and November. The problems are blamed on vehicle exhaust, industrial emissions, and burning garbage heaps. Egypt’s Environment Ministry has launched emergency efforts to reduce pollution from factories and dispose of massive trash mounds that have been burning. In October, the government ordered the closure of 25 factories in the city that burn tires for fuel, but apparently the step was not enough to solve the city’s air pollution woes.