A 20-year study of residents of a Cairo suburb shows that the tiny particles in polluted air could lead to three times as many long-term health problems as was previously thought. A connection between the number of particles in the air and health is suggested by Dr Razia of Cairo University. He and his colleagues collected data on 25,000 residents of Cairo over two decades.They found that as the number of tiny particles,those less than 2.5 microns in diameter, increased, so did the risk of dying form health problems such as heart attacks and lung cancer.