Toxicology deals with the study of adverse effects of chemical substances on biological system due to their exposure. It includes the study of mode of action of poison, symptoms of poison and treatments associated with poisoning along with their detection in biological system.

Branches of Toxicology

1.  Analytical Toxicology

It deals with the evaluation of toxic substances present in biological specimen as well as in raw form or crude form. And their evaluation involves identification and quantification of poisons using various analytical techniques.

2.  Clinical Toxicology

It deals with diagnosis and treatment of human poising.

3.  Forensic Toxicology

It deals with the analysis of toxic substances which involve various methods to study the poisonous substances to aid the legal investigation to know the cause of poisoning. It is a medico-legal aspect of clinical poisoning.

4.  Veterinary Toxicology

It is the specialised branch of toxicology which deals with the study, diagnosis and treatment of various toxic compounds present in the animal kingdom.

5.  Environmental Toxicology

It deals with the ill-effects of environmental toxicants on human, animal, plants and on the environment itself. Environmental toxicants are the compounds which are released into environment from various industries, hospitals, domestic wastage, etc, which may be degradable or non-degradable.

Categories of Poisons

1.  Corrosive Poisons

The poisons which cause inflammation on the site of contract are Corrosive Poisons, comprising of both Strong acids (concentrated Sulphuric acid, Nitric acid and Hydrochloric acid) and Alkalis.Strong bases: It includes both hydroxide and carbonate, i.e., Sodium hydroxide, Potassium hydroxide and Ammonium hydroxide etc. Carbonate: Sodium carbonate, Potassium carbonate etc.

2.  Irritant Poisons

The poisons which cause irritation, pain and excessive vomiting are known as Irritant Poisons, these poisons are further divided into:

                  (Inorganic Poisons)These poisons consist of both metallic (lead, arsenic, mercury, antimony, bismuth, silver, copper, zinc etc.) and non-metallic (zinc chloride, ferrus chloride, phosphate, sulphate, nitrate, nitrite etc.) compounds.

              (Organic Poisons)It consists of poisons of both vegetable and animal origin.Animal Poisons consist of Snakes venom, scorpion venom, cantharides etc.Vegetable Poisonsare the huge class of poisons which contains various plants which are toxic in nature (croton, castor, calotropis, nuxvomica, abrus, precatoreous, kaner etc.).

(Mechanical Poisons)The poisons which cause irritation, perforation, obstruction in the gastrointestinal tract, like powder glass, diamond dust, chopped hair etc.

3.  Neurotic Poisons

These poisons affect the different parts of central nervous system such as Cerebral Poisons (alcohol, opium, barbiturates, and benzodiazepines) are the examples of Ceberal poisons and are the Central Nervous System depressing agents, Spinal Poison, the most common example and important example of spinal poison in Strychnine, which is the active constituent that is derived from the seed of strychnux nuxvomica, Peripheral Poisons, these are the poisons which affects the peripheral nerves of the brain such as Curare.

4.  Cardiac Poisons

The poisons which affects the cardiac system, for example Digitalis, tobacco etc.

5.  Asphyxiate Poisons

This category of poison which cause asphyxia to the cells or tissues.Asphyxia is a condition of two sufficient supply of oxygen which results into shelter. The best and common example of Asphyxiate is Carbon dioxide, Carbon Monoxide.

Types of Poisons

1.  Solid Poisons

These poisons do not get absorbed easily into the blood. These should be dissolved in liquid to get absorbed. For example- Lead, Arsenic, Mercury etc.

2.  Liquid Poisons

These poisons contain both organic and inorganic liquid. Organic liquids are more volatile than inorganic liquids.

3.  Gaseous Poisons

These poisons are absorbed by inhalation such as carbon dioxide, carbon monoxide.

Medico-Legal Classification of Poisons

1.  Based on Intention

(A)  Homicidal Poisons

The poisons which are used to kill the other person are known as homicidal poisons such as aconite, abrus precatorius, arsenic, etc.

(B)  Suicidal Poisons

Those poisons which are used for self-killing such as opium, barbiturate, agricultural poisons etc.

(C)  Accidental Poisons

These poisons which cause toxicity by accidents or are used in mistaken of others: Snakes bite, CO are the examples of accidental poisons while sometimes child takes dhatura’s seeds in mistaken of capsicum seeds as these resemble to capsicum seeds.

(D)  Abortifacient Agents/ Poisons

The poisons which are used to procure abortion are known as abortifacient poisons for example Quinine (alkaloid), Calotropis, croton, oleander, marking nut etc.

(E)  Stupefying Agents/ Poisons

Those are the substances which are used to stupefy the human being. For example Dhatura, Chloral hydrate etc., these are used to rob the stranger or for the commitment of other crimes.

2. Bases of Method

(A) Volatile and Gaseous Poisons

Isolated by distillation are categorised into this group. And the volatile substances can be separated from gaseous.

Volatile substances are methanol, ethanol, benzene, toluene, acetone, chloroform, chloral hyderate etc.

Gaseous Poisons are ethane, butane etc.

(B)  Organic Non-Volatile Poisons

Isolated by solvent extraction methods include in this group. This is a very wide category of poison which contains rugs such as opiates and synthetic narcotics, sedatives, hypnotics, stimulants, etc.

These are the alkaloids that derive from opium, and operates are regulated under NDPS i.e., Narcotic Drugs and Psychotropic substances.

The muscle relaxant and are used to relieve anxiety. These are also CNS depressants.

LSD, amphetamine, cocaine etc. are the best examples of stimulants.

(C)  Metallic Poisons

The substances which are isolated by dry ash method or by wet digestion method constituting this group. The common poisons of this group are arsenic, lead, mercury, antimony, bismuth etc.

(D)  Anion

Anion is Isolated by dialysis. Most commonly encountered anions in poisoning cases are bromide, cyanide, fluoride, hypochlorite, nitrate, nitrite, phosphate, sulphite, sulphate etc.

Authors:

Navin Kumar Jaggi

Gurmeet Singh Jaggi