In the context of biology, poisons are substances that cause injury, illness, or death to organisms, usually by chemical reaction or other activity on the molecular scale. Some poisons are also toxins, and a distinction between the two terms is not always observed, even among scientists. The derivative forms "toxic" and "poisonous" are synonymous. Within chemistry and physics, a poison is a substance that obstructs or inhibits a reaction, for example by binding to a catalyst. Poisons have been known to be symbolized by the skull and crossbones (shown beside).
- 1 Biological poisoning
- 2 Classification of biological poisons by mechanism
- 2.1 Corrosives
- 2.2 Metabolic poisons (energy)
- 2.3 Neurotoxins
- 2.4 Teratogens (birth defects)
- 2.5 Mutagens (DNA damage)
- 2.6 Carcinogens (cancer)
- 3 Examples of biological poisons by source
- 4 Famous poisonings
- 5 Poisons in crime fiction
- 6 See also
Contact or absorption of poisons can cause rapid death or impairment. Agents that act on the nervous system can paralyze in seconds or less, and include both biologically derived neurotoxins and so-called nerve gases, which may be synthesized for warfare or industry. Inhaled or ingested cyanide almost instantly starves the body of energy by poisoning mitochondria and the synthesis of ATP. Intravenous injection of an unnaturally high concentration of potassium chloride, such as in the execution of prisoners in parts of the United States, quickly stops the heart by eliminating the cell potential necessary for muscle contraction. Such rapid reactions are often called acute poisoning.
Many substances regarded as poisons are toxic only indirectly. An example is "wood alcohol" or methanol, which is not poisonous itself, but is chemically converted to toxic formaldehyde in the liver. Many drug molecules are made toxic in the liver, and the genetic variability of certain liver enzymes makes the toxicity of many compounds differ between one individual and the next.
Milkweeds (Asclepias sp.) produce glycosides which are toxic to most organisms. (It is unlikely that any organism will eat much because of the extremely bitter taste.) Monarch butterfly larvae, however, are not susceptible to the toxin; in fact they accumulate it in their bodies as they eat the leaves of their host plant. Any predator who wishes to make a meal of an adult monarch will tend to be dissuaded by the bitter taste, and learn to leave the brightly colored insects alone. This gives considerable protection for monarchs from birds and other predators.
The study of the symptoms, mechanisms, treatment and diagnosis of biological poisoning is known as toxicology.
Exposure to radioactive substances can produce radiation poisoning, an unrelated phenomenon.
Classification of biological poisons by mechanism
Strong inorganic bases, such as lye, gradually dissolve skin on contact but can cause serious damage to eyes or mucous membranes much more rapidly. Ammonia is a far weaker base than lye, but has the distinction of being a gas and thus may more easily come into contact with the sensitive mucous membranes of the respiratory system. Quicklime, which has household uses, is a particularly common cause of poisoning. Some of the light metals, if handled carelessly, can not only cause thermal burns, but also produce very strongly basic solutions in sweat.
Poisons of this class are generally not very harmful to higher life forms such as humans, but lethal to microorganisms such as bacteria. Typical examples are ozone and chlorine, either of which is added nearly every municipal water supply in order to kill any harmful microorganisms present. All halogens are strong oxidizing agents, fluorine being the strongest of all.
- See also: Free radical
The most notable substance in this class is phosphorus.
Metabolic poisons (energy)
- By far the most notable substance in this class is carbon monoxide, which blocks the ability of red blood cells to transport oxygen.
- Fluoroacetate blocks a vital step in the citric acid cycle.
- Cyanide bonds with an enzyme involved in ATP production.
A common trait shared by heavy metals is the chronic nature of their toxicity. Low levels of heavy metal salts ingested over time accumulate in the body until toxic levels are reached.
Heavy metals are generally far more toxic when ingested in the form of soluble salts than in elemental form. For example, metallic mercury passes through the human digestive tract without interaction and is commonly used in dental fillings—even though mercury salts and inhaled mercury vapor are highly toxic.
- arsenic (see arsenic poisoning)
- beryllium (a highly toxic metal, but in no sense a heavy metal)
Neurotoxins interfere with nervous system functions and often lead to near-instant paralysis followed by rapid death. They include most spider and snake venoms, as well as many modern chemical weapons. One class of toxins of interest to neurochemical researchers are the various cone snail toxins known as conotoxins.
Cell Membrane Disrupters
- Nicotine - not strictly a neurotoxin, but capable in large doses of causing heart attack
Teratogens (birth defects)
Mutagens (DNA damage)
- Carbon tetrachloride (formerly used in fire extinguishers)
- Benzene (lab solvent, used in synthesis of various things)
- Some artificial sweeteners have been alleged to be carcinogenic. ex. Aspartame, Saccharin
- Dioxin - actually a group of many chemicals - has carcinogenic and other effects.
- Asbestos - a widely used insulating material that causes mesothelioma and other cancers
Examples of biological poisons by source
- Unfinished task: Items below should be added as examples under the appropriate poison class above.
Non-radioactive inorganic poisons
- Elemental metals
- Elemental metalloids
- Elemental nonmetals
- inorganic compounds
- Acids and bases, corrosives
Naturally produced poisons and toxins
- snake and spider venoms
- plant toxins (including many alkaloids)
- fungal toxins
- Ciguatera poisoning
- Scombroid poisoning
- Pyrrolizidine alkaloids
- Charles Darwin (Claimed only by rumor: self-medication with Fowler's solution, one percent potassium arsenite)
- Jamestown, Virginia colonists Standard historical accounts claim deaths by starvation, but the possibility of arsenic poisoning by rat poison (or of death by Bubonic plague) has also been reported (see http://www.pbs.org/wnet/secrets2/case3_clues.html).
- Jonestown inhabitants died from a poisoned drink in a mass suicide/murder: see Jonestown mass suicide
- Clare Boothe Luce (Did not die of her poisoning) See Arsenic
- Georgi Markov (Assassinated in London by KGB agents with ricin)
- Napoleon Bonaparte (Claimed only by rumor: killed by someone on his staff with arsenic.)
- Socrates According to Plato, killed by drinking Hemlock (water hemlock, not hemlock the evergreen tree)
- Alan Turing Apparently committed suicide by painting apple with Cyanide and taking a bite.
- Bhopal Disaster An accidental release of poisonous gas from a pesticide plant in India that killed over 2,000 people and injured many more.
- Love Canal: Buried toxic waste was covered and used as a building site for housing and school in Niagara Falls, New York, resulting in claims of chronic poisoning and a massive environmental cleanup.
Poisons in crime fiction
This is of course an inexhaustive list. You may wish to add other works and/or specify the poisons used.
- Anthony Berkeley: The Poisoned Chocolates Case
- Ann Granger: Say It With Poison
- Francis Iles: Before the Fact (filmed as Suspicion)
- Francis Iles: Malice Aforethought
- Agatha Christie: Three Act Tragedy
- Agatha Christie: A Pocket Full of Rye
- Agatha Christie: Crooked House
- Dorothy Sayers: The Unpleasantness at the Bellona Club
- Dorothy Sayers: Strong Poison
- Cornell Woolrich: Waltz into Darkness (filmed as Mississippi Mermaid and Original Sin)
- Joseph Kesselring: Arsenic and Old Lace (play)
- lead poisoning
- lethal injection
- Mithridates VI of Pontus
- Pesticide poisoning
- poisonous animals
- poisonous plants
- toxicity rating