"After the rice harvest each autumn, Egyptians take a deep breath and brace for the "black cloud", a thick layer of smog from burning rice straw that spreads across Cairo and the Nile valley for several weeks.
Environmentalists blame the burning of agricultural "waste", mostly rice straw, for the pall of smoke that turns the capital's already noxious air into an even more toxic mix.
Farmers produce about 30 million tonnes of what they see as waste each year. What they burn is responsible for 42 per cent of autumnal air pollution, the environmentalists say.
Rice straw has plenty of potential uses, experts contend." (Ahram Online/Reuters)