This introduction presents an overview of key concepts discussed in the subsequent chapters of this book. The book examines the logics underpinning the development of these regulatory regimes through an analysis of the tools that they have developed and implemented. A variety of tools for managing toxicants and their effects was developed in the 1950s in the national and international regulatory systems some of which had already been experimented with before the war. The idea of setting limit values for exposure was born long before the 1950s. At the time, the American Conference of Governmental Industrial Hygienists (ACGIH) started to produce Maximum Allowable Concentration values (MACs) for toxic substances present in work environment. These shifts in the logics underpinning the management of toxic substances took place in the framework of unprecedented growth of regulatory authorities. Many solutions have been proposed, and many policies tried and tested to manage this toxic heritage and the permanent flow of dangerous substances in circulation.