Poison
Poison is any substance which acts in a pathological manner. The definition of poison is complicated, identified by the ancient Greek philosopher and scientist Paracelsus, who stated that “all substances are poisons, dependent on their dosage.” Medically this is the general consensus also. Practically, however, many substances are of course innocuous in a low enough dosage - indeed one encountered in day-to-day life. Examples here would include nitrogen, chalk, water, etc. (though water toxicity may occur following hypothalamic compromise such as after taking noradrenaline (norepinephrine in the USA) reuptake inhibitors such as MDMA/Ecstasy). Other substances are very damaging in minute doses - notably the irreversible acetylcholinesterase inhibitors such as VX and Tabun (now employed in chemical warfare), heavy metals such as lead and mercury.
It is erroneous and extremely misleading and confusing in a clinical setting to use the words “poison” and “toxin” interchangeably. Poison is defined above, whereas a toxin is a poison derived from an organism. For example; excessive urea in the blood (from renal injury) and snake venom are toxins, whereas cadmium is a heavy metal poison but not a toxin. This error includes describing a poisonous substance as being “toxic”.
Examples
- Snippet from Wikipedia: Poison
A poison is any chemical substance that is harmful or lethal to living organisms. The term is used in a wide range of scientific fields and industries, where it is often specifically defined. It may also be applied colloquially or figuratively, with a broad sense.
Whether something is considered a poison or not may depend on the amount, the circumstances, and what living things are present. Poisoning could be accidental or deliberate, and if the cause can be identified there may be ways to neutralise the effects or minimise the symptoms.
In biology, a poison is a chemical substance causing death, injury or harm to organisms or their parts. In medicine, poisons are a kind of toxin that are delivered passively, not actively. In industry the term may be negative, something to be removed to make a thing safe, or positive, an agent to limit unwanted pests. In ecological terms, poisons introduced into the environment can later cause unwanted effects elsewhere, or in other parts of the food chain.