Over the past fifteen years regulatory agencies have relied on their approaches to characterise and control the release of toxic substances into the aquatic environment: a GC/MS analysis for U.S. EPA designated 126 priority pollutants and 132 dangerous substances according to the European 76/464/CEE Directive and on the bioassays with aquatic bioorganisms."Emerging Contaminants" correspond in most cases to irregulated contaminants, e.g. surfactants, pharmaceuticals and personal care products (PPCP), or gasoline additives.These two volumes, 5/I and 5/O, of this Handbook deal with the analytical, toxicological and environmental issues of these toxicants. Based on results of up-to-date research they give the reader a balanced view on this rapidly developing and complex subject.