"A vast cloud of pollution has descended on Cairo once more, creating health problems and challenging authorities as they seek ways to stop it coming back. Every year since 1999, an autumnal cloud has appeared above the Egyptian capital, already one of the world's most polluted cities, with the thick bitter-smelling fog reducing visibility and making the throat and eyes prickle.
Environmentalists say the pollution is causing severe damage to people's health in the capital, home to nearly a quarter of the country's 70 million inhabitants and almost half a million vehicles.
According to the toxicology department of Cairo's Qasr el-Ayni University hospital, the cloud exacerbates respiratory and cardio-vascular illnesses, causing at least 5,000 additional deaths in the metropolis and its surroundings every year.
The cloud's main causes are ever-increasing road traffic, hundreds of factories that do not comply with anti-pollution regulations (including steel works, diesel-fuelled power stations, cement and brick factories and coal-fired ovens), growing mountains of rubbish and the burning of rice straw in the surrounding countryside.
Some three million tonnes of straw go up in smoke around the capital every year, as farmers burn what's left on the ground to clear fields for the next crop. The process is banned, but continues as there is currently no alternative for getting rid of the straw. Thanks to a drop in atmospheric pressure at this time of year and the absence of cleansing winds, the polluting dust accumulates above the city, enveloping it in a smokey pall and the smell of burnt straw."
EDIT
http://www.terradaily.com/2004/041119043911.064h0383.html