What is toxicology?

The study of poison is called toxicology and focuses upon the identification and quantification of the adverse, meaning unfavourable or harmful, effects directly caused by the physical or chemical agents.  In toxicology, the term toxicity is the degree to which a substance (a poison) can harm humans or animals meaning that toxicity is the measure of how poisonous a molecule is. A common measure of toxicity is the LD50, the lethal dose fifty per cent which is the amount of a chemical that can be expected to cause death in half of a group of a certain animal species when the chemical enters the body through skin absorption or indigestion.  This is usually expressed as milligrams of chemical per kilogram of body weight.  A chemical with a small LD50, such as five mg/kg, is considered to be “very highly toxic” while a chemical with a high LD50, such as five thousand mg/ kg, is almost considered to be non-toxic. However, it should be noted that this measurement for toxicity does not include the non-lethal effects that the substance may have upon the organism [8]. The toxicity of molecules is affected by several characteristics and properties of both the molecule and the organism that has received the dosage.