This problem of increased pollution in the major cities of the world has led to an increase in the number of studies done to look at the effects on our health. The results so far are not very reassuring. In fact ,air pollution may be a much greater danger to our health than scientists believed before.A 20-year study of residents of a Cairo suburb shows that the tiny particles in polluted air coold lead to three time as many long-term health problems as was previously thought.