Poison
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.
Human antimicrobial peptides which are toxic to viruses, fungi, bacteria, and cancerous cells are considered a part of the immune system.
For example, food-industry wastewater—which may contain potato juice or milk—can be hazardous to the ecosystems of streams and rivers by consuming oxygen and causing eutrophication, but is nonhazardous to humans and not classified as a poison.
Examples include medicines (e.g. anthelmintics used on chickens[9][10]), solvents (e.g. rubbing alcohol, turpentine), cleaners (e.g. bleach, ammonia), coatings (e.g. arsenic wallpaper), and feedstocks.
By the principle of entropy, chemical contamination is typically costly or infeasible to reverse, unless specific chelating agents or micro-filtration processes are available.
Chelating agents are often broader in scope than the acute target, and therefore their ingestion necessitates careful medical or veterinarian supervision.
Pesticides are one group of substances whose prime purpose is their toxicity to various insects and other animals deemed to be pests (e.g., rats and cockroaches).
Natural pesticides have been used for this purpose for thousands of years (e.g. concentrated table salt is toxic to many slugs and snails).
Bioaccumulation of chemically-prepared agricultural insecticides is a matter of concern for the many species, especially birds, which consume insects as a primary food source.
Selective toxicity, controlled application, and controlled biodegradation are major challenges in herbicide and pesticide development and in chemical engineering generally, as all lifeforms on earth share an underlying biochemistry; organisms exceptional in their environmental resilience are classified as extremophiles, these for the most part exhibiting radically different susceptibilities.
A poison which enters the food chain—whether of industrial, agricultural, or natural origin—might not be immediately toxic to the first organism that ingests the toxin, but can become further concentrated in predatory organisms further up the food chain, particularly carnivores and omnivores, especially concerning fat soluble poisons which tend to become stored in biological tissue rather than excreted in urine or other water-based effluents.
Naturally occurring sour gas is a fast-acting atmospheric poison, which can be released by volcanic activity or drilling rigs.
[12] In modern society, cases of suspicious death elicit the attention of the Coroner's office and forensic investigators.
In mammals, chemical poisons are often passed from mother to offspring through the placenta during gestation, or through breast milk during nursing.
These are often of human origin, but pollution can also include unwanted biological processes such as toxic red tide, or acute changes to the natural chemical environment attributed to invasive species, which are toxic or detrimental to the prior ecology (especially if the prior ecology was associated with human economic value or an established industry such as shellfish harvesting).
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.
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.
An example is "wood alcohol" or methanol, which is not poisonous itself, but is chemically converted to toxic formaldehyde and formic acid in the liver.
Dogs and cats are not natural herbivores, but a chemical defense developed by Theobroma cacao can be incidentally fatal nevertheless.
For instance, phosgene is a highly reactive nucleophile acceptor, which makes it an excellent reagent for polymerizing diols and diamines to produce polycarbonate and polyurethane plastics.
Humans and animals, lacking this hormone and its receptor, are unaffected by this, and need to ingest relatively large doses before any toxicity appears.
For example, the 14th-century Chinese text of the Huolongjing written by Jiao Yu outlined the use of a poisonous gunpowder mixture to fill cast iron grenade bombs.
[26] In Medieval Europe, it was common for monarchs to employ personal food tasters to thwart royal assassination, in the dawning age of the Apothecary.
[27] The figurative term poison pen letter became well known in 1913 by a notorious criminal case in Pennsylvania, U.S.; the phrase dates to 1898.
