international pictogram for<unk> ous substances. The skull and crossbones has long been a standard symbol for<unk> . In biology,<unk> s are substances that can cause death, injury or harm to organs, tissues, cells, and DNA usually by chemical reactions or other activity on the molecular scale, when an organism is exposed to a sufficient quantity. In a metaphorical broader use of term it may refer to any thing deemed harmful. The fields of medicine (particularly veterinary medicine) and zoology often distinguish a<unk>  from a toxin, and from a venom. Both<unk>  and venom are toxins, which are toxicants produced by organisms in nature. The difference between venom and<unk>  is the delivery method of the toxin. Venoms are toxins that are actively delivered by being injected via a bite or sting through a venom apparatus, such as fangs or a stinger, in a process called envenomation, whereas<unk> s are toxins that are passively delivered by being swallowed, inhaled, or absorbed through the skin. Industry, agriculture, and other sectors employ many<unk> ous substances, usually for reasons other than their toxicity. For example, many are important feedstocks, solvents, cleaners, coatings, and so on. Even the toxicity itself sometimes has economic value, when it serves agricultural purposes of weed control and pest control. Most<unk> ous industrial compounds have associated material safety data sheets and are classed as hazardous substances. Hazardous substances are subject to extensive regulation on production, procurement and use in overlapping domains of occupational safety and health, public health, drinking water quality standards, air pollution and environmental protection. Due to the mechanics of molecular diffusion, many<unk> ous compounds rapidly diffuse into biological tissues, air, water, or soil on a molecular scale. 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 toxicity to various insects and other animals deemed to be pests (e.g., rats and cockroaches) is their prime purpose. Natural pesticides have been used for this purpose for thousands of years (e.g. concentrated table salt is toxic to many slugs). 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<unk>  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<unk> s which tend to become stored in biological tissue rather than excreted in urine or other water-based effluents. Apart from food, many<unk> s readily enter the body through the skin and lungs. Hydrofluoric acid is a notorious contact<unk> , in addition to its corrosive damage. Naturally occurring sour gas is a notorious, fast-acting atmospheric<unk>  (as released by volcanic activity or drilling rigs). Plant-based contact irritants, such as that possessed by<unk>  ivy or<unk>  oak, are often classed as allergens rather than<unk> s; the effect of an allergen being not a<unk>  as such, but to turn the body's natural defenses against itself.<unk>  can also enter the body through faulty medical implants, or by injection (which is the basis of lethal injection in the context of capital punishment). In 2013, 3.3 million cases of unintentional human<unk> ings occurred. This resulted in 98,000 deaths worldwide, down from 120,000 deaths in 1990. In modern society, cases of suspicious death elicit the attention of the Coroner's office and forensic investigators. Of increasing concern since the isolation of natural radium by Marie and Pierre Curie in 1898—and the subsequent advent of nuclear physics and nuclear technologies—are radiological<unk> s. These are associated with ionizing radiation, a mode of toxicity quite distinct from chemically active<unk> s. In mammals, chemical<unk> s are often passed from mother to offspring through the placenta during gestation, or through breast milk during nursing. In contrast, radiological damage can be passed from mother or father to offspring through genetic mutation, which—if not fatal in miscarriage or childhood, or a direct cause of infertility—can then be passed along again to a subsequent generation. Atmospheric radon is a natural radiological<unk>  of increasing impact since humans moved from hunter-gatherer lifestyles though cave dwelling to increasingly enclosed structures able to contain radon in dangerous concentrations. The 2006<unk> ing of Alexander Litvinenko was a novel use of radiological assassination, presumably meant to evade the normal investigation of chemical<unk> s.<unk> s widely dispersed into the environment are known as pollution. 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). The scientific disciplines of ecology and environmental resource management study the environmental life cycle of toxic compounds and their complex, diffuse, and highly interrelated effects.
Poison
Tin poisoning
Xenointoxication
Mushroom poisoning
Secondary poisoning
Cyanide poisoning
Chinese alchemical elixir poisoning
Theobromine poisoning