The last few years have seen a burgeoning of interest in airborne particles and the environmental problems which they can cause. For example, when Krakatowa erupted, the dust cloud formed by the particles it emitted was measured for four years afterwards and in 1997 the same has been seen happening in Montserrat. The implications are far reaching, not just on the level of human inhalation, but the particles can also act as catalysts in the air and speed up unwanted large scale processes like global warming and ozone depletion. A further example is that research has indicated that lead...