Classification of Poisons

The poisons are classified on the basis of

A. Mode of action
B. Chemical Nature

Both classifications have their own importance in forensic investigation. Mode of action helps in
determining the type of poisons and chemical nature helps in analyzing it.

Classification of poison on the basis of mode of action:

A mode of action defines a functional or anatomical modification, at cellular level, stemming

1. Corrosive Poisons: Corrosive is a substance that has a corroding and destructive effect
on the human body. A corrosive poison is simply a highly active irritant and not only
produces inflammation but also ulceration of the tissues. Basically a corrosive poison
destroys and erodes the surface with which it comes in contact i.e they produce local
 action. Acids are potent desiccants with the ability to produce a coagulation necrosis and
eschar formation of injured tissue. On the other hand, alkalis produce a liquefaction
necrosis of tissue.

2. Irritant Poisons: An irritant poison is only a milder form of a corrosive. In other words,
a corrosive, when diluted or taken in a less concentrated form, becomes an irritant.
Irritant poisons cause pain in the abdomen, vomiting and purging. It is classified as
● Inorganic irritant poisons: The inorganic subgroup consists of non-metallic and
metallic poisons. Examples of non-metallic poisons are phosphorus, chlorine,
bromine, iodine etc. examples of metallic poisons include arsenic, antimony,
bismuth, lead etc.
● Organic irritant poisons: This group of poisons includes animal and plant
poisons. Examples of plant poisons include marking nut, calotropis, dhatura etc.
Examples of animal poisons include snakes, insects, cantharides etc.
● Mechanical irritant poisons: This group includes coarsely powdered glass,
chopped hairs, diamond dust, dried sponge etc.
 3. Systemic Poisons: This class of poisons affects the main organs of the body system and
therefore they are referred to as systemic poisons.
● Cardiac poisons: These are poisons having main action on the heart, either directly
or through the nerves. Nicotine, aconite, oleander and digitalis are important in this
group.
● Spinal poisons: These poisons act on the spinal cord. It includes strychnine and
gelsemium.
● Cerebral poisons: The poisons acting on the cerebrum may have a somniferous,
inebriant or delirium effect. The somniferous group includes opioids, the inebriant
includes alcohols, anaesthetics, sedatives etc. The deliriants includes dhatura,
belladonna, cannabis indica.
● Asphyxiants: It includes irrespirable or toxic gases. These gases displace oxygen
from the ambient air and reduce the partial pressure of available oxygen. It includes
irrespirable gases such as carbon monoxide, carbon dioxide, sewer gases and some
war gases.
● Peripheral poisons: The peripheral nervous system consists of the nerves that branch
out from the brain and spinal cord. These nerves form the communication network
between the CNS and the body parts. The peripheral poisons affect the peripheral
nervous system. The poisons acting on the peripheral nerves include curare and
conium.

Classification of poison on the basis of nature of poison:

1. Gaseous Poisons: These types of poison are in gaseous state and if inhaled, hamper the
ability of the blood as a carrier of oxygen and may damage the tissues of the air passages
and lungs. Some examples of gaseous poisons are carbon monoxide, carbon dioxide,
hydrogen sulphide, sulphur oxide, chlorine, nitrous oxide, tear gas etc.
2. Volatile Inorganic Poisons: Acute poisoning with volatile substances usually follows the
slow inhalation of vapors in order to become intoxicated. Cyanide, phosphine, arsine,
phosgene, chloride, etc. are few Volatile Inorganic Poisons.
3. Volatile Organic Poisons: These are organic chemicals that have a high vapor pressure
at ordinary room temperature. The high vapor pressure which results from a low boiling
point, causes large numbers of molecules to sublimate from the liquid or solid form of the
compound and enter the surrounding air. Examples of Volatile Organic Poisons are
ethanol, formaldehyde, and acetaldehyde.
4. Non-Volatile Inorganic (anions) Poisons: Examples are halides, dichromate, chlorates,
azides , nitrites ,sulfate, phosphide , cyanide etc.
5. Non-Volatile Inorganic (cations) Poisons: Examples are mercury, arsenic, barium,
thallium, lead, antimony, bismuth etc.
6. Non-Volatile Organic Neutral Poisons (pesticides): Examples of Non-Volatile Organic
Neutral Poisons are organophosphates, organochlorines, carbamates, pyrethroids
7. Non-Volatile Organic Acidic Compound (acidic drugs): Drugs/ Poisons, which are
acidic in nature, are called Acidic Drugs. These drugs readily react with bases to form
salts. Few of the examples are barbiturates, sulpha, phenolic compounds (Phenol, Cresols
etc.), salicylates.
8. Non-Volatile Organic Alkaline Compounds (basic drugs): If the drugs contain a
nitrogen atom with a lone pair of electrons available for reaction with protons they will
behave as bases only Examples alkaloids, benzodiazepine.
9. Miscellaneous Poisons: These poisons may be organic or inorganic, volatile or
non-volatile and or animal, plant origin or toxins produced thereof.
● Mechanical poisons: diamond dust, glass powder, chopped hair.
● Food poisoning: (mycotoxins)
● Animal /insect poisons: snake venom, scorpion, bees, ants

Prepared By-
Manisha Panda
Assistant Professor, SoFS, CUTM BBSR