Aerosol particles in the air, such as diesel exhaust particles [DPE] and sulphate particles, are seriously connected to the global environmental issues of the earth: warming temperature phenomenon and acid rain. But since these minute particles have complex qualities and undergo changes in time and space, it is very difficult to gain a clear understanding of how much influence on the surroundings they have. This book, based on Japan-China collaborative research, supplies a basic guideline for those interested in the air environment and its improvement.