Toxicology can be defined as the branch of science that deals with poisons, and a poison can be defined as any substance that causes a harmful effect when administrated, either by accident or design, to a living organism. By convention, toxicology also includes the study of harmful effects caused by physical phenomena, such as radiation of various kinds and noise. The history of Toxicology dates back to the early humans who used animal and plant poisons for hunting and warfare.
The Ebers papyrus (circa 1500 BC) describes several poisons known at that time. For example, it mentions hemlock as the state poison of the Greeks as well as opium, aconite and heavy metals such as lead, copper and antimony. Hippocrates (circa 400 B. C. ) introduced clinical toxicology principles by describing elemental concepts of bioavailability and overdose. There are also several citations of the use of poisons in ancient Greece literature. It was Dioscorides, a Greek pharmacist, who made the first attempt to classify poisons.
De Materia Medica, his 5-volume systematic description of approximately 600 different plants and 1000 different medications, became the first systematic pharmacopoeia. Socrates (470-399 B. C. ) poisoning by drinking hemlock is one of the best known cases of execution by poisoning. The use of poisonings was also a very common practice in Roman politics, reaching peak numbers during the fourth century B. C. It continued until the year 82 B. C. when the first law against poisoning was issued, named the Lex Cornelia.
The study of toxicology serves society in many ways, not only to protect humans and the environment from the deleterious effects of toxicants but also to facilitate the development of more selective toxicants such as anticancer and other clinical drugs and pesticides. Poison is a quantitative concept, almost any substance being harmful at some doses but, at the same time, being without harmful effect at some lower dose. Between these two limits there is a range of possible effects, from subtle long-term chronic toxicity to immediate lethality. Vinyl chloride may be taken as an example.
It is a potent hepatotoxic at high doses, a carcinogen with a long latent period at lower doses, and apparently without effect at very low doses. There are several different studies of toxicology but I will only name a few. For starters, Clinical toxicology, which is in a hospital setting, deals with emergencies such as overdoses, poisonings, and attempted suicides. Moreover, Forensic toxicology is the medical-legal aspects of poisonings; it establishes relationships between tissue residual level and probable cause of death.