Humans have been using chemical substances of different kinds and classes for a very long time and in practically every aspect of life. Chemical substances have the inherent ability to react with a host of factors and, to multiple physical and biological conditions. The reactive properties of chemical substances differ widely. Chemical substances when not properly used, stored, and/or managed are known to cause harmful health effects to users and occupational workers, are workplace hazards, and damage the living environment. Therefore, it is important to determine the potential hazards of each chemical substance before they come in contact with animals, humans, and the living environment. In other words, chemical substances of different categories (refer to Chapter 1) used and handled by the general public and society should be evaluated.