title: Parasitism

text: As hosts and parasites evolve together, their relationships often change. When a parasite is in a sole relationship with a host, selection drives the relationship to become more benign, even mutualistic, as the parasite can reproduce for longer if its host lives longer. But where parasites are competing, selection favours the parasite that reproduces fastest, leading to increased virulence. There are thus varied possibilities in host–parasite coevolution.


title: Parasitism

text: Evolutionary epidemiology analyses how parasites spread and evolve, whereas Darwinian medicine applies similar evolutionary thinking to non-parasitic diseases like cancer and autoimmune conditions.


title: Parasitism

text: Long-term coevolution sometimes leads to a relatively stable relationship tending to commensalism or mutualism, as, all else being equal, it is in the evolutionary interest of the parasite that its host thrives. A parasite may evolve to become less harmful for its host or a host may evolve to cope with the unavoidable presence of a parasite—to the point that the parasite's absence causes the host harm. For example, although animals parasitised by worms are often clearly harmed, such infections may also reduce the prevalence and effects of autoimmune disorders in animal hosts, including humans. In a more extreme example, some nematode worms cannot reproduce, or even survive, without infection by "Wolbachia" bacteria.


title: Parasitism

text: Lynn Margulis and others have argued, following Peter Kropotkin's 1902 "", that natural selection drives relationships from parasitism to mutualism when resources are limited. This process may have been involved in the symbiogenesis which formed the eukaryotes from an intracellular relationship between archaea and bacteria, though the sequence of events remains largely undefined.


title: Parasitism

text: Competition between parasites can be expected to favour faster reproducing and therefore more virulent parasites, by natural selection.


title: Parasitism

text: Among competing parasitic insect-killing bacteria of the genera "Photorhabdus" and "Xenorhabdus", virulence depended on the relative potency of the antimicrobial toxins (bacteriocins) produced by the two strains involved. When only one bacterium could kill the other, the other strain was excluded by the competition. But when caterpillars were infected with bacteria both of which had toxins able to kill the other strain, neither strain was excluded, and their virulence was less than when the insect was infected by a single strain.


title: Parasitism

text: A parasite sometimes undergoes cospeciation with its host, resulting in the pattern described in Fahrenholz's rule, that the phylogenies of the host and parasite come to mirror each other.


title: Parasitism

text: An example is between the simian foamy virus (SFV) and its primate hosts. The phylogenies of SFV polymerase and the mitochondrial cytochrome c oxidase subunit II from African and Asian primates were found to be closely congruent in branching order and divergence times, implying that the simian foamy viruses cospeciated with Old World primates for at least 30 million years.


title: Parasitism

text: The presumption of a shared evolutionary history between parasites and hosts can help elucidate how host taxa are related. For instance, there has been a dispute about whether flamingos are more closely related to storks or ducks. The fact that flamingos share parasites with ducks and geese was initially taken as evidence that these groups were more closely related to each other than either is to storks. However, evolutionary events such as the duplication, or the extinction of parasite species (without similar events on the host phylogeny) often erode similarities between host and parasite phylogenies. In the case of flamingos, they have similar lice to those of grebes. Flamingos and grebes do have a common ancestor, implying cospeciation of birds and lice in these groups. Flamingo lice then switched hosts to ducks, creating the situation which had confused biologists.


title: Parasitism

text: Parasites infect sympatric hosts (those within their same geographical area) more effectively, as has been shown with digenetic trematodes infecting lake snails. This is in line with the Red Queen hypothesis, which states that interactions between species lead to constant natural selection for coadaptation. Parasites track the locally common hosts' phenotypes, so the parasites are less infective to allopatric hosts, those from different geographical regions.


title: Parasitism

text: Some parasites modify host behaviour in order to increase their transmission between hosts, often in relation to predator and prey (parasite increased trophic transmission). For example, in the California coastal salt marsh, the fluke "Euhaplorchis californiensis" reduces the ability of its killifish host to avoid predators. This parasite matures in egrets, which are more likely to feed on infected killifish than on uninfected fish. Another example is the protozoan "Toxoplasma gondii", a parasite that matures in cats but can be carried by many other mammals. Uninfected rats avoid cat odors, but rats infected with "T. gondii" are drawn to this scent, which may increase transmission to feline hosts. The malaria parasite modifies the skin odour of its human hosts, increasing their attractiveness to mosquitoes and hence improving the chance that the parasite will be transmitted. The spider "Cyclosa argenteoalba" often have parasitoid wasp larvae attached to them which alter their web-building behavior. Instead of producing their normal sticky spiral shaped webs, they made simplified webs when the parasites were attached. This manipulated behavior lasted longer and was more prominent the longer the parasites were left on the spiders.


title: Parasitism

text: Parasites can exploit their hosts to carry out a number of functions that they would otherwise have to carry out for themselves. Parasites which lose those functions then have a selective advantage, as they can divert resources to reproduction. Many insect ectoparasites including bedbugs, batbugs, lice and fleas have lost their ability to fly, relying instead on their hosts for transport. Trait loss more generally is widespread among parasites. An extreme example is the myxosporean "Henneguya zschokkei", an ectoparasite of fish and the only animal known to have lost the ability to respire aerobically: its cells lack mitochondria.


title: Parasitism

text: Hosts have evolved a variety of defensive measures against their parasites, including physical barriers like the skin of vertebrates, the immune system of mammals, insects actively removing parasites, and defensive chemicals in plants.


title: Parasitism

text: The evolutionary biologist W. D. Hamilton suggested that sexual reproduction could have evolved to help to defeat multiple parasites by enabling genetic recombination, the shuffling of genes to create varied combinations. Hamilton showed by mathematical modelling that sexual reproduction would be evolutionarily stable in different situations, and that the theory's predictions matched the actual ecology of sexual reproduction. However, there may be a trade-off between immunocompetence and breeding male vertebrate hosts' secondary sex characteristics, such as the plumage of peacocks and the manes of lions. This is because the male hormone testosterone encourages the growth of secondary sex characteristics, favouring such males in sexual selection, at the price of reducing their immune defences.


title: Parasitism

text: The physical barrier of the tough and often dry and waterproof skin of reptiles, birds and mammals keeps invading microorganisms from entering the body. Human skin also secretes sebum, which is toxic to most microorganisms. On the other hand, larger parasites such as trematodes detect chemicals produced by the skin to locate their hosts when they enter the water. Vertebrate saliva and tears contain lysozyme, an enzyme that breaks down the cell walls of invading bacteria. Should the organism pass the mouth, the stomach with its hydrochloric acid, toxic to most microorganisms, is the next line of defence. Some intestinal parasites have a thick, tough outer coating which is digested slowly or not at all, allowing the parasite to pass through the stomach alive, at which point they enter the intestine and begin the next stage of their life. Once inside the body, parasites must overcome the immune system's serum proteins and pattern recognition receptors, intracellular and cellular, that trigger the adaptive immune system's lymphocytes such as T cells and antibody-producing B cells. These have receptors that recognise parasites.


title: Parasitism

text: Insects often adapt their nests to reduce parasitism. For example, one of the key reasons why the wasp "Polistes canadensis" nests across multiple combs, rather than building a single comb like much of the rest of its genus, is to avoid infestation by tineid moths. The tineid moth lays its eggs within the wasps' nests and then these eggs hatch into larvae that can burrow from cell to cell and prey on wasp pupae. Adult wasps attempt to remove and kill moth eggs and larvae by chewing down the edges of cells, coating the cells with an oral secretion that gives the nest a dark brownish appearance.


title: Parasitism

text: Plants respond to parasite attack with a series of chemical defences, such as polyphenol oxidase, under the control of the jasmonic acid-insensitive (JA) and salicylic acid (SA) signalling pathways. The different biochemical pathways are activated by different attacks, and the two pathways can interact positively or negatively. In general, plants can either initiate a specific or a non-specific response. Specific responses involve recognition of a parasite by the plant's cellular receptors, leading to a strong but localised response: defensive chemicals are produced around the area where the parasite was detected, blocking its spread, and avoiding wasting defensive production where it is not needed. Non-specific defensive responses are systemic, meaning that the responses are not confined to an area of the plant, but spread throughout the plant, making them costly in energy. These are effective against a wide range of parasites. When damaged, such as by lepidopteran caterpillars, leaves of plants including maize and cotton release increased amounts of volatile chemicals such as terpenes that signal they are being attacked; one effect of this is to attract parasitoid wasps, which in turn attack the caterpillars.


title: Parasitism

text: Parasitism and parasite evolution were until the twenty-first century studied by parasitologists, in a science dominated by medicine, rather than by ecologists or evolutionary biologists. Even though parasite-host interactions were plainly ecological and important in evolution, the history of parasitology caused what the evolutionary ecologist Robert Poulin called a "takeover of parasitism by parasitologists", leading ecologists to ignore the area. This was in his opinion "unfortunate", as parasites are "omnipresent agents of natural selection" and significant forces in evolution and ecology. In his view, the long-standing split between the sciences limited the exchange of ideas, with separate conferences and separate journals. The technical languages of ecology and parasitology sometimes involved different meanings for the same words. There were philosophical differences, too: Poulin notes that, influenced by medicine, "many parasitologists accepted that evolution led to a decrease in parasite virulence, whereas modern evolutionary theory would have predicted a greater range of outcomes".


title: Parasitism

text: Their complex relationships make parasites difficult to place in food webs: a trematode with multiple hosts for its various life cycle stages would occupy many positions in a food web simultaneously, and would set up loops of energy flow, confusing the analysis. Further, since nearly every animal has (multiple) parasites, parasites would occupy the top levels of every food web.


title: Parasitism

text: Parasites can play a role in the proliferation of non-native species. For example, invasive green crabs are minimally affected by native trematodes on the Eastern Atlantic coast. This helps them outcompete native crabs such as the rock and Jonah crabs.


title: Parasitism

text: Ecological parasitology can be important to attempts at control, like during the campaign for eradicating the Guinea worm. Even though the parasite was eradicated in all but four countries, the worm began using frogs as an intermediary host before infecting dogs, making control more difficult than it would have been if the relationships had been better understood.


title: Parasitism

text: Although parasites are widely considered to be harmful, the eradication of all parasites would not be beneficial. Parasites account for at least half of life's diversity; they perform important ecological roles; and without parasites, organisms might tend to asexual reproduction, diminishing the diversity of traits brought about by sexual reproduction. Parasites provide an opportunity for the transfer of genetic material between species, facilitating evolutionary change. Many parasites require multiple hosts of different species to complete their life cycles and rely on predator-prey or other stable ecological interactions to get from one host to another. The presence of parasites thus indicates that an ecosystem is healthy.


title: Parasitism

text: An ectoparasite, the California condor louse, "Colpocephalum californici", became a well-known conservation issue. A major and very costly captive breeding program was run in the United States to rescue the California condor. It was host to a louse, which lived only on it. Any lice found were "deliberately killed" during the program, to keep the condors in the best possible health. The result was that one species, the condor, was saved and returned to the wild, while another species, the parasite, became extinct.


title: Parasitism

text: Although parasites are often omitted in depictions of food webs, they usually occupy the top position. Parasites can function like keystone species, reducing the dominance of superior competitors and allowing competing species to co-exist.


title: Parasitism

text: A single parasite species usually has an aggregated distribution across host animals, which means that most hosts carry few parasites, while a few hosts carry the vast majority of parasite individuals. This poses considerable problems for students of parasite ecology, as it renders parametric statistics as commonly used by biologists invalid. Log-transformation of data before the application of parametric test, or the use of non-parametric statistics is recommended by several authors, but this can give rise to further problems, so quantitative parasitology is based on more advanced biostatistical methods.


title: Parasitism

text: Human parasites including roundworms, the Guinea worm, threadworms and tapeworms are mentioned in Egyptian papyrus records from 3000 BC onwards; the Ebers Papyrus describes hookworm. In ancient Greece, parasites including the bladder worm are described in the Hippocratic Corpus, while the comic playwright Aristophanes called tapeworms "hailstones". The Roman physicians Celsus and Galen documented the roundworms "Ascaris lumbricoides" and "Enterobius vermicularis".


title: Parasitism

text: In his "Canon of Medicine", completed in 1025, the Persian physician Avicenna recorded human and animal parasites including roundworms, threadworms, the Guinea worm and tapeworms.


title: Parasitism

text: In his 1397 book "Traité de l'état, science et pratique de l'art de la Bergerie" (Account of the state, science and practice of the art of shepherding), wrote the first description of a trematode endoparasite, the sheep liver fluke "Fasciola hepatica".


title: Parasitism

text: In the early modern period, Francesco Redi's 1668 book "Esperienze Intorno alla Generazione degl'Insetti" ("Experiences of the Generation of Insects"), explicitly described ecto- and endoparasites, illustrating ticks, the larvae of nasal flies of deer, and sheep liver fluke. Redi noted that parasites develop from eggs, contradicting the theory of spontaneous generation. In his 1684 book "Osservazioni intorno agli animali viventi che si trovano negli animali viventi" ("Observations on Living Animals found in Living Animals"), Redi described and illustrated over 100 parasites including the large roundworm in humans that causes ascariasis. Redi was the first to name the cysts of "Echinococcus granulosus" seen in dogs and sheep as parasitic; a century later, in 1760, Peter Simon Pallas correctly suggested that these were the larvae of tapeworms.


title: Parasitism

text: In 1681, Antonie van Leeuwenhoek observed and illustrated the protozoan parasite "Giardia lamblia", and linked it to "his own loose stools". This was the first protozoan parasite of humans to be seen under a microscope. A few years later, in 1687, the Italian biologists Giovanni Cosimo Bonomo and Diacinto Cestoni described scabies as caused by the parasitic mite "Sarcoptes scabiei", marking it as the first disease of humans with a known microscopic causative agent.


title: Parasitism

text: Modern parasitology developed in the 19th century with accurate observations and experiments by many researchers and clinicians; the term was first used in 1870. In 1828, James Annersley described amoebiasis, protozoal infections of the intestines and the liver, though the pathogen, "Entamoeba histolytica", was not discovered until 1873 by Friedrich Lösch. James Paget discovered the intestinal nematode "Trichinella spiralis" in humans in 1835. James McConnell described the human liver fluke, "Clonorchis sinensis", in 1875. Algernon Thomas and Rudolf Leuckart independently made the first discovery of the life cycle of a trematode, the sheep liver fluke, by experiment in 1881–1883. In 1877 Patrick Manson discovered the life cycle of the filarial worms that cause elephantiasis transmitted by mosquitoes. Manson further predicted that the malaria parasite, "Plasmodium", had a mosquito vector, and persuaded Ronald Ross to investigate. Ross confirmed that the prediction was correct in 1897–1898. At the same time, Giovanni Battista Grassi and others described the malaria parasite's life cycle stages in "Anopheles" mosquitoes. Ross was controversially awarded the 1902 Nobel prize for his work, while Grassi was not. In 1903, David Bruce identified the protozoan parasite and the tsetse fly vector of African trypanosomiasis.


title: Parasitism

text: Given the importance of malaria, with some 220 million people infected annually, many attempts have been made to interrupt its transmission. Various methods of malaria prophylaxis have been tried including the use of antimalarial drugs to kill off the parasites in the blood, the eradication of its mosquito vectors with organochlorine and other insecticides, and the development of a malaria vaccine. All of these have proven problematic, with drug resistance, insecticide resistance among mosquitoes, and repeated failure of vaccines as the parasite mutates. The first and as of 2015 the only licensed vaccine for any parasitic disease of humans is RTS,S for "Plasmodium falciparum" malaria.


title: Parasitism

text: Poulin observes that the widespread prophylactic use of anthelmintic drugs in domestic sheep and cattle constitutes a worldwide uncontrolled experiment in the life-history evolution of their parasites. The outcomes depend on whether the drugs decrease the chance of a helminth larva reaching adulthood. If so, natural selection can be expected to favour the production of eggs at an earlier age. If on the other hand the drugs mainly affects adult parasitic worms, selection could cause delayed maturity and increased virulence. Such changes appear to be underway: the nematode "Teladorsagia circumcincta" is changing its adult size and reproductive rate in response to drugs.


title: Parasitism

text: In the classical era, the concept of the parasite was not strictly pejorative: the "parasitus" was an accepted role in Roman society, in which a person could live off the hospitality of others, in return for "flattery, simple services, and a willingness to endure humiliation".


title: Parasitism

text: The satirical cleric Jonathan Swift alludes to hyperparasitism in his 1733 poem "On Poetry: A Rhapsody", comparing poets to "vermin" who "teaze and pinch their foes":


title: Parasitism

text: A 2022 study examined the naming of some 3000 parasite species discovered in the previous two decades. Of those named after scientists, over 80% were named for men, whereas about a third of authors of papers on parasites were women. The study found that the percentage of parasite species named for relatives or friends of the author has risen sharply in the same period.


title: Parasitism

text: In Bram Stoker's 1897 Gothic horror novel "Dracula", and its many film adaptations, the eponymous Count Dracula is a blood-drinking parasite (a vampire). The critic Laura Otis argues that as a "thief, seducer, creator, and mimic, Dracula is the ultimate parasite. The whole point of vampirism is sucking other people's blood—living at other people's expense."


title: Parasitism

text: Disgusting and terrifying parasitic alien species are widespread in science fiction, as for instance in Ridley Scott's 1979 film "Alien". In one scene, a Xenomorph bursts out of the chest of a dead man, with blood squirting out under high pressure assisted by explosive squibs. Animal organs were used to reinforce the shock effect. The scene was filmed in a single take, and the startled reaction of the actors was genuine.


title: Shenyang J-16

text: The Shenyang J-16 (Chinese: 歼-16) is a Chinese advanced fourth-generation, tandem-seat, twinjet, multirole strike fighter developed from the Shenyang J-11 (itself derived from the Sukhoi Su-27) and built by Shenyang Aircraft Corporation. It is operated by the People's Liberation Army Air Force (PLAAF).


title: Shenyang J-16

text: In the 1990s, China purchased Sukhoi Su-27 air superiority fighters from Russia, including those license-produced in China as the Shenyang J-11A. The J-11A was further developed into the J-11B single seat and BS twin seat variant with indigenous technology. The J-16 is a strike aircraft derived from the J-11BS model.


title: Shenyang J-16

text: The J-16 is equipped with an AESA radar and is powered by two Chinese Shenyang WS-10A turbofan engines. Weight is reduced through greater use of composite materials. J-16 units have received radar-absorbent paint to reduce its radar signature, and enhance its Suppression of Enemy Air Defenses (SEAD) capability in conjunction with electronic support measure pods.


title: Shenyang J-16

text: The cockpit is fitted with helmet-mounted display (HMD) system to improve pilot’s situational awareness.


title: Shenyang J-16

text: The electronic warfare version of the fighter, named J-16D, was developed in 2010s. The aircraft reportedly made its first flight in 2015. J-16D is designed to suppress enemy air defenses (SEAD), capable of housing internal jamming equipment and carrying various external electronic warfare pods.


title: Shenyang J-16

text: According to aviation researcher Justin Bronk of the Royal United Services Institute, J-16 holds advantages over Russian Flanker variants with its wide application of composite materials, longer range missiles, advanced sensors, and avionics. J-16 represents a transition by the Chinese aviation industry away from a past dependence on Russian technology towards developing modern derivatives that are superior to the Russian originals in many aspects.


title: Shenyang J-16

text: The Chinese military is developing advanced autonomous capabilities for its combat aircraft. In March 2021, it was reported that a J-16 variant with the backseat co-pilot replaced by an artificial intelligence algorithm called "intelligence victory" () was undergoing testing at Shenyang Aircraft Corporation. A similar aircraft was also spotted by satellite image at an experimental test base near Malan, Xinjiang in June 2021.


title: Shenyang J-16

text: The J-16 entered service in 2015 and was officially revealed in 2017 during the People's Liberation Army's 90th anniversary parade.


title: Shenyang J-16

text: According to the Australian Department of Defence, on 26 May 2022 a J-16 intercepted a RAAF P-8 Poseidon surveillance aircraft over the South China Sea while the latter was conducting routine maritime surveillance operations over international waters. The newly elected Australian defence minister Richard Marles said that the J-16 first flew closely alongside the P-8, released flares and then flew in front of the P-8 where it released chaff into the flight path of which some were ingested by the P-8's engine. The Australian Government lodged a protest with the Chinese Government over the incident and Marles said that Australia would not be deterred from conducting operations of the same or a similar nature in the future. According to a Chinese defense ministry spokesman, the Australian pilots acted "dangerously and provocatively," and ignored repeated warnings before the J-16 drove the Australian aircraft away. An article by the Lowy Institute, an Australian thinktank, said the interception marked an escalation in the grey zone actions that China was using to enforce its claims in the South China Sea.


title: Shenyang J-16

text: Out of all aircraft deployed in the Taiwan strait, J-16 fighters are the most frequently used, possibly due to its electronic warfare capabilities. In August 2022, China dispatched large amount of J-16 fighters to the Taiwan strait, in response to the Nancy Pelosi’s Taiwan visit.


title: Major non-NATO ally

text: Major non-NATO ally (MNNA) is a designation given by the United States government to close allies that have strategic working relationships with the US Armed Forces but are not members of the North Atlantic Treaty Organization (NATO). While the status does not automatically include a mutual defense pact with the United States, it confers a variety of military and financial advantages that otherwise are not obtainable by non-NATO countries. There are currently 19 major non-NATO allies across four continents (11 in Asia, three in Africa, three in South America, and two in Oceania).


title: Major non-NATO ally

text: MNNA status was first created in 1987 when section 2350a, otherwise known as the Sam Nunn Amendment, was added to Title 10 (Armed Forces) of the United States Code by Congress. It stipulated that cooperative research and development agreements could be enacted with non-NATO allies by the Secretary of Defense with the concurrence of the Secretary of State. The initial MNNAs were Australia, Egypt, Israel, Japan, and South Korea.


title: Major non-NATO ally

text: In 1996, major non-NATO allies received additional military and financial benefits when section 2321k was added to Title 22 (Foreign Relations) of the US Code (also known as section 517 of the Foreign Assistance Act of 1961), which added MNNAs to many of the same exemptions from the Arms Export Control Act that were enjoyed by NATO members. It also authorized the President to designate a nation as an MNNA thirty days after notifying Congress. When enacted, the statute designated the initial five countries as major non-NATO allies, and added Jordan and New Zealand to the list.


title: Major non-NATO ally

text: In 1998, President Bill Clinton named Argentina as an ally for the "Argentine compromise and contribution to international peace and security" materialized in its participation in the Gulf War (being the only South American country to do so), and for its continuing support of United Nations peacekeeping missions.


title: Major non-NATO ally

text: In 2019, Donald Trump designated Brazil as a major non-NATO ally after receiving a working visit from Brazilian President Jair Bolsonaro.


title: Major non-NATO ally

text: In March 2022, Joe Biden designated Colombia as a major non-NATO ally. Biden said: "I've said for a long time Colombia is a keystone to our shared efforts to build a hemisphere as prosperous, secure and democratic ... Today I'm proud to announce that I intend to designate Colombia a major non-NATO ally ... that's exactly what you are".


title: Major non-NATO ally

text: In May 2015, US President Barack Obama declared his intention to make Tunisia a non-NATO ally while hosting his Tunisian counterpart Beji Caid Essebsi at the White House.


title: Major non-NATO ally

text: The designation of certain countries as major non-NATO allies has not been without controversy. In 2017, US Representatives Ted Poe (R-TX) and Rick Nolan (D-MN) introduced H.R. 3000, a bill to revoke Pakistan's position as an MNNA, citing inadequate counterterrorism efforts, the harboring of Osama bin Laden and Pakistani support for the Taliban. The bill never received a vote. In 2021, US Representative Andy Biggs introduced H.R. 35, another version of the legislation.


title: Major non-NATO ally

text: In 2017, General Joseph Dunford, chairman of the Joint Chiefs of Staff, accused Pakistan's Inter-Services Intelligence (ISI) of having ties to terror groups. Reuters reported that "possible Trump administration responses being discussed include expanding U.S. drone strikes and perhaps eventually downgrading Pakistan's status as a major non-NATO ally."


title: Major non-NATO ally

text: On January 31, 2022, President Joe Biden announced that Qatar would be made a major non-NATO ally, citing its assistance during the US withdrawal from Afghanistan in August 2021.


title: Major non-NATO ally

text: When Congress enacted on September 30, 2002, the Foreign Relations Authorization Act for FY 2003, it required that Taiwan be "treated as though it were designated a major non-NATO ally." Despite some initial misgivings about Congress's perceived intrusion into the President's foreign affairs authority, the Bush administration subsequently submitted a letter to Congress on August 29, 2003, designating Taiwan as a major non-NATO ally.


title: Major non-NATO ally

text: Around the same time, invitations were sent to the ASEAN members Thailand and the Philippines, both of whom accepted. Singapore was reportedly offered a similar arrangement, but turned down the offer.


title: Major non-NATO ally

text: US–New Zealand strategic and military cooperation suffered a setback after the breakdown of the ANZUS alliance in 1984 over nuclear ship entry. The designation of New Zealand as an MNNA in 1997 reflected the warming of relations between the two. In June 2012 New Zealand signed a partnership arrangement with NATO further strengthening and consolidating relations.


title: Major non-NATO ally

text: In 2014, following the annexation of Crimea by the Russian Federation, a bill was introduced to the United States Congress to grant major non-NATO ally status to Georgia, Moldova, and Ukraine. A bill to make Ukraine a major non-NATO ally was introduced into the US House of Representatives in May 2019. As of 2022, these changes have not been made despite support from the US Commission on Security and Cooperation in Europe, also known as the Helsinki Commission, following the Russian invasion of Ukraine.


title: Major non-NATO ally

text: During a 2015 Camp David summit with the Gulf Cooperation Council states, the Obama administration considered designating Saudi Arabia, the United Arab Emirates (UAE), Oman, and Qatar as MNNAs. Qatar has since been designated as an MNNA.


title: Major non-NATO ally

text: In June 2019, US lawmakers provided for enhancements to India's status, though this fell short of making them a MNNA.


title: Major non-NATO ally

text: According to Finnish newspapers in early March 2022, following the Russian invasion of Ukraine, Finland and Sweden had planned to apply for major non-NATO ally status. Since then, the two countries have applied for membership of NATO itself.


title: Major non-NATO ally

text: In December 2014, the US House passed the United States–Israel Strategic Partnership Act of 2013. This new category would have placed Israel one notch above the Major Non-NATO Ally classification and would have added additional support for defense and energy infrastructure, and strengthened cooperation through business and academics. The bill additionally called for the US to increase their war reserve stock in Israel to US$1.8 billion. The bill did not reach a vote, and as such did not pass or become law.


title: Major non-NATO ally

text: In 2016, the US recognized India as a "major defense partner". This occurred less than a month after the House of Representatives passed the US India Defense Technology and Partnership Act. This allowed India to buy more advanced and sensitive technologies that is on par with that of US' closest allies and partners. The U.S. has four "foundational agreements" that it signs with India.


title: Major non-NATO ally

text: The following countries have been designated as major non-NATO allies of the United States in chronological order of their designation. In addition, an act provides that the Republic of China (Taiwan) shall be treated as an MNNA, without formal designation as such:


title: Emily Alyn Lind

text: Emily Alyn Lind (born 2001/2002) is an American actress. She began her career as a child actress, when she was known for her recurring role as young Amanda Clarke on the ABC series "Revenge", and for her role as Ariel on the CBS medical drama "Code Black". Lind has also starred in the Netflix original films "The Babysitter" and "" as Melanie, and in the theatrical film "Doctor Sleep" as Snakebite Andi. Since 2021, she has starred as Audrey Hope in the HBO Max teen drama series "Gossip Girl".


title: Emily Alyn Lind

text: Lind is the daughter of producer John Lind and actress Barbara Alyn Woods. She has an older sister, Natalie Alyn Lind, and a younger sister, Alyvia Alyn Lind, who are also actresses.


title: Emily Alyn Lind

text: Lind made her film debut as a child actress in 2008 in "The Secret Life of Bees". Since then she has appeared in such films as "Dear Dumb Diary", "Enter the Void", "J. Edgar", "", and "Movie 43". She has played Emma Lavery in the soap opera "All My Children".


title: Emily Alyn Lind

text: Lind has had recurring roles in the ABC television series "Revenge" as young Amanda Clarke, as well as in the ABC television series "Eastwick" as Emily Gardener. She has also appeared in such series as "Days of Our Lives", "Medium", "Flashpoint", "Criminal Minds", "Suburgatory", and "Hawaii Five-0". In 2017, Lind was promoted to a starring role on the CBS medical drama "Code Black" for the series' third season, after appearing as the character of Ariel during the show's first two seasons.


title: Emily Alyn Lind

text: Lind starred as Melanie in the comedy horror film, "The Babysitter", which was released on Netflix in 2017. She reprised her role in the sequel, "". In 2018, Lind was cast as Snakebite Andi in the 2019 film "Doctor Sleep", based on the Stephen King novel and sequel to "The Shining".


title: Emily Alyn Lind

text: In March 2020, it was announced that Lind is set to star in the HBO Max teen drama "Gossip Girl", which debuted in 2021.


title: Multimedia

text: Multimedia is a form of communication that uses a combination of different content forms such as text, audio, images, animations, or video into a single interactive presentation, in contrast to traditional mass media, such as printed material or audio recordings, which features little to no interaction between users. Popular examples of multimedia include video podcasts, audio slideshows and animated videos. Multimedia also contains the principles and application of effective interactive communication such as the building blocks of software, hardware, and other technologies.


title: Multimedia

text: Multimedia can be recorded for playback on computers, laptops, smartphones, and other electronic devices, either on demand or in real time (streaming). In the early years of multimedia, the term "rich media" was synonymous with interactive multimedia. Over time, hypermedia extensions brought multimedia to the World Wide Web.


title: Multimedia

text: The term "multimedia" was coined by singer and artist Bob Goldstein (later 'Bobb Goldsteinn') to promote the July 1966 opening of his "Lightworks at L'Oursin" show in Southampton, Long Island. Goldstein was perhaps aware of an American artist named Dick Higgins, who had two years previously discussed a new approach to art-making he called "intermedia".


title: Multimedia

text: While the term didn't exist yet, the idea of "multimedia" could be taken back to when the 19th century composer Richard Wagner believed in the concept of "Gesamtkunstwerk", meaning 'total artwork'. Wagner strived to combine multiple art forms- opera, drama, music - to create a perfect synthesis on stage. He looked down on the Grand Opera at the time, which emphasized individual talent, rather than the complete work as a whole. By combining these art forms, Wagner believed the most profound art could be made.


title: Multimedia

text: On August 10, 1966, Richard Albarino of "Variety" borrowed the terminology, reporting: "Brainchild of song scribe-comic Bob ('Washington Square') Goldstein, the 'Lightworks' is the latest "multi-media" music-cum-visuals to debut as discothèque fare." Two years later, in 1968, the term "multimedia" was re-appropriated to describe the work of a political consultant, David Sawyer, the husband of Iris Sawyer—one of Goldstein's producers at L'Oursin.


title: Multimedia

text: In the 1993 first edition of "Multimedia: Making It Work", Tay Vaughan declared "Multimedia is any combination of text, graphic art, sound, animation, and video that is delivered by computer. When you allow the user – the viewer of the project – to control what and when these elements are delivered, it is "interactive multimedia". When you provide a structure of linked elements through which the user can navigate, interactive multimedia becomes "hypermedia"."


title: Multimedia

text: The German language society Gesellschaft für deutsche Sprache recognized the word's significance and ubiquitousness in the 1990s by awarding it the title of German 'Word of the Year' in 1995. The institute summed up its rationale by stating "[Multimedia] has become a central word in the wonderful new media world".


title: Multimedia

text: In common usage, "multimedia" refers to an electronically delivered combination of media including video, still images, audio, and text in such a way that can be accessed interactively. Much of the content on the web today falls within this definition as understood by millions. Some computers which were marketed in the 1990s were called "multimedia" computers because they incorporated a CD-ROM drive, which allowed for the delivery of several hundred megabytes of video, picture, and audio data. That era saw also a boost in the production of educational multimedia CD-ROMs. A standard CD-ROM can hold on average 700 megabytes of data, while the maximum size a 3.5 inch floppy disk can hold is 2.8 megabytes, with an average of 1.44 megabytes.


title: Multimedia

text: The term "video", if not used exclusively to describe motion photography, is ambiguous in multimedia terminology. "Video" is often used to describe the file format, delivery format, or presentation format instead of ""footage"" which is used to distinguish motion photography from ""animation"" of rendered motion imagery. Multiple forms of information content are often not considered modern forms of presentation such as audio or video. Likewise, single forms of information content with single methods of information processing (e.g. non-interactive audio) are often called multimedia, perhaps to distinguish static media from active media. In the fine arts, for example, Leda Luss Luyken's ModulArt brings two key elements of musical composition and film into the world of painting: variation of a theme and movement of and within a picture, making "ModulArt" an interactive multimedia form of art. Performing arts may also be considered multimedia considering that performers and props are multiple forms of both content and media.


title: Multimedia

text: In modern times, a multimedia device can be referred to an electronic device, such as a smartphone, a videogame system, or a computer. Each and everyone of these devices have a main function, but also have other uses beyond their intended purpose, such as reading, writing, recording video, streaming listening to music, and playing video games. This has lend them to be called "multimedia devices". While previous media was always local, many are now handled through web based solutions, particularly streaming.


title: Multimedia

text: Multimedia presentations are presentations featuring multiple types of media. The different types of media can include videos, animations, audio or photos. Through these different types of media, they can convey a message to their target audience and effectively communicate with them. One example that is commonly used is video. Videos are a great visual example to use in multimedia presentation because it can create a visual aid to an idea that is mentioned. If used in an education setting, this can benefit students, as they would be able to retain the information better. Another example of multimedia presentations used is charts and graphs. With the help of charts and graphs, this can allow the presenter to show their audience trends and the data associated with their research. This can give the audience a visual idea of how the company is doing.


title: Multimedia

text: Multimedia games and simulations may be used in a physical environment with special effects, with multiple users in an online network, or locally with an offline computer, game system, or simulator.


title: Multimedia

text: The various formats of technological or digital multimedia may be intended to enhance the users' experience, for example to make it easier and faster to convey information. Or in entertainment or art, combine an array of artistic insights that includes elements from different art forms to engage, inspire, or captivate an audience.


title: Multimedia

text: Enhanced levels of interactivity are made possible by combining multiple forms of media content. Online multimedia is increasingly becoming object-oriented and data-driven, enabling applications with collaborative end-user innovation and personalization on multiple forms of content over time. Examples of these range from multiple forms of content on Web sites like photo galleries with both images (pictures) and title (text) user-updated, to simulations whose co-efficients, events, illustrations, animations or videos are modifiable, allowing the multimedia "experience" to be altered without reprogramming. In addition to seeing and hearing, haptic technology enables virtual objects to be felt. Emerging technology involving illusions of taste and smell may also enhance the multimedia experience.


title: Multimedia

text: Multimedia finds its application in various areas including, but not limited to, advertisements, art, education, entertainment, engineering, medicine, mathematics, business, scientific research and spatial temporal applications. Several examples are as follows:


title: Multimedia

text: Creative industries use multimedia for a variety of purposes ranging from fine arts, to entertainment, to commercial art, to journalism, to media and software services provided for any of the industries listed below. An individual multimedia designer may cover the spectrum throughout their career. Request for their skills range from technical, to analytical, to creative.


title: Multimedia

text: Much of the electronic old and new media used by commercial artists in multimedia.. Advertising companies rely heavily on social interfaces and television to promote products. Using these platforms, they are able to express their message or persuade a targeted audience. Business to business and interoffice communications are often developed by creative services firms for advanced multimedia presentations beyond simple slide shows to sell ideas or liven up training. Commercial multimedia developers may be hired to design for governmental services and nonprofit services applications as well. In addition, the prominence of data mining within multimedia platforms in order to adjust marketing techniques based on the data they mine is a crucial and notable practice of commercial advertisement to efficiently understand the demographic of a target audience.


title: Multimedia

text: Multimedia is heavily used in the entertainment industry, especially to develop special effects in movies and animations (VFX, 3D animation, etc.). Multimedia games are a popular pastime and are software programs available either as CD-ROMs or online. Video games class as multimedia, as such games meld animation, audio, and, most importantly, interactivity, to allow the player an immersive experience. While video games can vary in terms of animation style or audio type or even lack thereof, the element of interactivity makes them a striking example of "interactive multimedia". "Interactive multimedia" defines multimedia applications that allow users to actively participate instead of just sitting by as passive recipients of information.


title: Multimedia

text: In the arts there are multimedia artists, whose minds are able to blend techniques using different media that in some way incorporates interaction with the viewer. Another approach entails the creation of multimedia that can be displayed in a traditional fine arts arena, such as an art gallery. Although multimedia display material may be volatile, the survivability of the content is as strong as any traditional media. Digital recording material may be just as durable and infinitely reproducible with perfect copies every time.


title: Multimedia

text: In education, multimedia is used to produce computer-based training courses (popularly called CBTs) and reference books like encyclopedia and almanacs. A CBT lets the user go through a series of presentations, text about a particular topic, and associated illustrations in various information formats.


title: Multimedia

text: Learning theory in the past decade has expanded dramatically because of the introduction of multimedia. Several lines of research have evolved, e.g. cognitive load and multimedia learning.


title: Multimedia

text: From multimedia learning (MML) theory, David Roberts has developed a large group lecture practice using PowerPoint and based on the use of full-slide images in conjunction with a reduction of visible text (all text can be placed in the notes view’ section of PowerPoint). The method has been applied and evaluated in 9 disciplines. In each experiment, students’ engagement and active learning have been approximately 66% greater, than with the same material being delivered using bullet points, text, and speech, corroborating a range of theories presented by multimedia learning scholars like Sweller and Mayer. The idea of media convergence is also becoming a major factor in education, particularly higher education. Defined as separate technologies such as voice (and telephony features), data (and productivity applications), and video that now share resources and interact with each other, media convergence is rapidly changing the curriculum in universities all over the world. Higher education has been implementing the use of social media applications such as Twitter, YouTube, Facebook, etc. to increase student collaboration and develop new processes in how information can be conveyed to students.


title: Multimedia

text: Multimedia provides students with an alternate means of acquiring knowledge designed to enhance teaching and learning through various mediums and platforms. In the 1960s, technology began to expand into the classrooms through devices such as screens and telewriters. This technology allows students to learn at their own pace and gives teachers the ability to observe the individual needs of each student. The capacity for multimedia to be used in multi-disciplinary settings is structured around the idea of creating a hands-on learning environment through the use of technology. Lessons can be tailored to the subject matter as well as be personalized to the students' varying levels of knowledge on the topic. Learning content can be managed through activities that utilize and take advantage of multimedia platforms. This kind of usage of modern multimedia encourages interactive communication between students and teachers and opens feedback channels, introducing an active learning process especially with the prevalence of new media and social media. Technology has impacted multimedia as it is largely associated with the use of computers or other electronic devices and digital media due to its capabilities concerning research, communication, problem-solving through simulations and feedback opportunities. The innovation of technology in education through the use of multimedia allows for diversification among classrooms to enhance the overall learning experience for students.


title: Multimedia

text: Multimedia is a robust education methodology within the social work context. The five different multimedia which supports the education process are narrative media, interactive media, communicative media, adaptive media, and productive media. Contrary to long-standing belief, multimedia technology in social work education existed before the prevalence of the internet. It takes the form of images, audio, and video into the curriculum.


title: Multimedia

text: First introduced to social work education by Seabury & Maple in 1993, multimedia technology is utilized to teach social work practice skills including interviewing, crisis intervention, and group work. In comparison with conventional teaching method, including face-to-face courses, multimedia education shortens transportation time, increases knowledge and confidence in a richer and more authentic context for learning, generates interaction between online users, and enhances understanding of conceptual materials for novice students.


title: Multimedia

text: In an attempt to examine the impact of multimedia technology on students’ study, A. Elizabeth Cauble & Linda P. Thurston conducted a research in which Building Family Foundations (BFF), an interactive multimedia training platform, was utilized to assess social work students’ reactions to multimedia technology on variables of knowledge, attitudes, and self-efficacy. The results states that respondents show a substantial increase in academic knowledge, confidence, and attitude. Multimedia also benefits students because it brings expert to students online, fits students’ schedule, allows students to choose courses that suit them.


title: Multimedia

text: Mayer's Cognitive Theory of Multimedia Learning suggests, "people learn more from words and pictures than from words alone." According to Mayer and other scholars, multimedia technology stimulates people's brains by implementing visual and auditory effects, and thereby assists online users to learn efficiently. Researchers suggest that when users establish dual channels while learning, they tend to understand and memorize better. Mixed literature of this theory are still present in the field of multimedia and social work.


title: Multimedia

text: With the spread and development of the English language around the world, multimedia has become an important way of communicating between different people and cultures. Multimedia Technology creates a platform where language can be taught. The traditional form of teaching English as a Second Language in classrooms have drastically changed with the prevalence of technology, making easier for students to obtain language learning skills. Multimedia motivates students to learn more languages through audio, visual and animation support. It also helps create English contexts since an important aspect of learning a language is developing their grammar, vocabulary and knowledge of pragmatics and genres. In addition, cultural connections in terms of forms, contexts, meanings and ideologies have to be constructed. By improving thought patterns, multimedia develops students’ communicative competence by improving their capacity to understand the language. One of the studies, carried out by Izquierdo, Simard and Pulido, presented the correlation between "Multimedia Instruction (MI) and learners’ second language (L2)" and its effects on learning behavior. Their findings based on Gardner's theory of the "socio-educational model of learner motivation and attitudes", the study shows that there is easier access to language learning materials as well as increased motivation with MI along with the use of Computer-Assisted Language Learning.


title: Multimedia

text: Newspaper companies all over are trying to embrace the new phenomenon by implementing its practices in their work. While some have been slow to come around, other major newspapers like "The New York Times", "USA Today" and "The Washington Post" are setting the precedent for the positioning of the newspaper industry in a globalized world. To keep up with the changing world of multimedia, journalistic practices are adopting and utilizing different functions of multimedia through the inclusions of visuals such as varying audio, video, text, etc. in their writings.


title: Multimedia

text: News reporting is not limited to traditional media outlets. Freelance journalists can make use of different new media to produce multimedia pieces for their news stories. It engages global audiences and tells stories with technology, which develops new communication techniques for both media producers and consumers. The Common Language Project, later renamed to The Seattle Globalist, is an example of this type of multimedia journalism production.


title: Multimedia

text: Multimedia reporters who are mobile (usually driving around a community with cameras, audio and video recorders, and laptop computers) are often referred to as mojos, from "mo"bile "jo"urnalist.


title: Multimedia

text: Software engineers may use multimedia in computer simulations for anything from entertainment to training such as military or industrial training. Multimedia for software interfaces are often done as a collaboration between creative professionals and software engineers. Multimedia helps expand the teaching practices that can be found in engineering to allow for more innovated methods to not only educated future engineers, but to help evolve the scope of understanding of where multimedia can be used in specialized engineer careers like software engineers.


title: Multimedia

text: Multimedia is also allowing major car manufactures, such as Ford, and General Motors, to expand the design, and safety standards of their cars. By using a game engine and virtual reality glasses, these companies are able to test the safety features, and the design of the car, before a prototype is even made. Building a car virtually reduces the time it takes to produce new vehicles, cutting down on the time needed to test designs, and allowing the designers to make changes in real time. It also reduces expenses, since with a virtual car making real world prototypes is no longer needed.


title: Multimedia

text: In mathematical and scientific research, multimedia is mainly used for modeling and simulation. For example, a scientist can look at a molecular model of a particular substance and manipulate it to arrive at a new substance. Representative research can be found in journals such as the "Journal of Multimedia". One well known example of this being applied would be in the movie Interstellar where Executive Director Kip Thorne helped create one of the most realistic depictions of a blackhole in film. The visual effects team under Paul Franklin took Kip Thorne's mathematical data and applied it into their own visual effects engine called "Double Negative Gravitational Renderer" a.k.a. "Gargantua", to create a "real" blackhole, used in the final cut. Later on the visual effects team went onto publish a blackhole study


title: Multimedia

text: Medical professionals and students have a wide variety of ways to learn new techniques and procedures through interactive media and online courses and lectures. The methods of conveying information to students have drastically evolved with the help of multimedia. From the 1800s to today, lessons are commonly taught using chalkboards. Projected aids, such as the epidiascope and slide projectors, were introduced into the classrooms around the 1960s. With the growing use of computers, the medical field has begun to incorporate new devices and procedures to assist in teaching students, performing procedures, and analyzing patient data. As well as providing that data in a meaningful way to the patients.


title: Multimedia

text: Virtual reality is a platform for multimedia in which it merges all categories of multimedia into one virtual environment. It has gained much more attention over recent years following technological advancements and is becoming much more commonly used nowadays for various uses like virtual showrooms and video games. Virtual reality was first introduced in 1957 by cinematographer Morton Heilig in the form of an arcade-style booth called Sensorama. The first virtual reality headset was created by American computer scientist Ivan Sutherland and Bob Sproull, his student, in 1968. Virtual reality is used for educational and also recreational purposes like watching movies, interactive video games, simulations etc. Ford Motor Company uses this technology to show customers the interior and exterior of their cars via their Immersion Lab. In Pima County, Arizona their police force is trained by using Virtual Reality to create scenarios for police to practice in. Many video game platforms now support virtual reality technology, including Sony's PlayStation, Nintendo's Switch as part of their Labo project, as well as the Oculus VR headsets that can be used for Xbox and PC gaming, with it being more preferable to pair with a PC due to it only being compatible with the original Xbox One and providing limited capabilities.


title: Multimedia

text: Augmented reality became widely popular only in the 21st century; however, some of the earlier versions of such were things like the Sega Genesis Activator Controller back in 1992 which allowed users to literally stand in an octagon and control in game movement with physical movement or to stretch back even further the R.O.B. NES Robot back in 1984 which with its array of accessories was able to also provide users with the sensation of holding a firearm. These multimedia input devices are among some of the earliest of the augmented reality devices by allowing users to input commands to facilitate a different user experience.


title: Multimedia

text: While virtual reality strives to be a totally immersive multimedia experience, completely replacing reality with a digital simulation, augmented reality limits itself to overlaying digital output or content onto the real world. Augmented reality can be defined as "an enhanced version of reality created by the use of technology to overlay digital information on an image of something being viewed through a device (such as a smartphone camera)". Augmented reality systems can be used for tasks such as overlaying speed, altitude and heading information on an aircraft Heads-Up Display, or projecting images or animations into a real-life scene, such as in the game Pokémon Go. Sony uses augmented reality technology in their PlayStation 5 controllers with their haptic feedback feature to give users a greater sense of immersion while playing video games. For example, while users are playing Call of Duty and want to shoot their gun at the enemy, the triggers on the controller will provide tension to the player that will make it feel like they are actually pulling the trigger on a gun. The game Astro's Playroom that comes with a PlayStation 5 console showcases the different ways a game can make players feel more immersed and the depth and potential that the haptic feedback feature has for the future of gaming.


title: Multimedia

text: In Europe, the reference organisation for the multimedia industry is the European Multimedia Associations Convention.


title: Radon

text: Radon is a chemical element with the symbol Rn and atomic number 86. It is a radioactive, colourless, odourless, tasteless noble gas. It occurs naturally in minute quantities as an intermediate step in the normal radioactive decay chains through which thorium and uranium slowly decay into various short-lived radioactive elements and lead. Radon itself is the immediate decay product of radium. Its most stable isotope, Rn, has a half-life of only 3.8 days, making it one of the rarest elements. Since thorium and uranium are two of the most common radioactive elements on Earth, while also having three isotopes with half-lives on the order of several billion years, radon will be present on Earth long into the future despite its short half-life. The decay of radon produces many other short-lived nuclides, known as "radon daughters", ending at stable isotopes of lead.


title: Radon

text: Unlike all other intermediate elements in the aforementioned decay chains, radon is, under standard conditions, gaseous and easily inhaled, and therefore a health hazard. It is often the single largest contributor to an individual's background radiation dose, but due to local differences in geology, the level of exposure to radon gas differs from place to place. A common source is uranium-containing minerals in the ground, and therefore it accumulates in subterranean areas such as basements. Radon can also occur in some ground water like spring waters and hot springs. Climate change may cause radon previously trapped underground to be released as permafrost thaws, particularly in areas like the Arctic, Alaska, Canada, Greenland and Russia. It is possible to test for radon and use techniques such as sub slab depressurization for mitigation.


title: Radon

text: Epidemiological studies have shown a clear link between breathing high concentrations of radon and incidence of lung cancer. Radon is a contaminant that affects indoor air quality worldwide. According to the United States Environmental Protection Agency (EPA), radon is the second most frequent cause of lung cancer, after cigarette smoking, causing 21,000 lung cancer deaths per year in the United States. About 2,900 of these deaths occur among people who have never smoked. While radon is the second most frequent cause of lung cancer, it is the number one cause among non-smokers, according to EPA policy-oriented estimates. Significant uncertainties exist for the health effects of low-dose exposures. Unlike the gaseous radon itself, radon daughters are solids and stick to surfaces, such as airborne dust particles, which can cause lung cancer if inhaled.


title: Radon

text: Radon is a colorless, odorless, and tasteless gas and therefore is not detectable by human senses alone. At standard temperature and pressure, it forms a monatomic gas with a density of 9.73 kg/m, about 8 times the density of the Earth's atmosphere at sea level, 1.217 kg/m. It is one of the densest gases at room temperature and is the densest of the noble gases. Although colorless at standard temperature and pressure, when cooled below its freezing point of , it emits a brilliant radioluminescence that turns from yellow to orange-red as the temperature lowers. Upon condensation, it glows because of the intense radiation it produces. It is sparingly soluble in water, but more soluble than lighter noble gases. It is appreciably more soluble in organic liquids than in water. Its solubility equation is as follows,


title: Radon

text: where formula_2 is the molar fraction of radon, formula_3 is the absolute temperature, and formula_4 and formula_5 are solvent constants.


title: Radon

text: Radon is a member of the zero-valence elements that are called noble gases, and is chemically not very reactive. The 3.8-day half-life of radon-222 makes it useful in physical sciences as a natural tracer. Because radon is a gas at standard conditions, unlike its decay-chain parents, it can readily be extracted from them for research.


title: Radon

text: It is inert to most common chemical reactions, such as combustion, because the outer valence shell contains eight electrons. This produces a stable, minimum energy configuration in which the outer electrons are tightly bound. Its first ionization energy—the minimum energy required to extract one electron from it—is 1037 kJ/mol. In accordance with periodic trends, radon has a lower electronegativity than the element one period before it, xenon, and is therefore more reactive. Early studies concluded that the stability of radon hydrate should be of the same order as that of the hydrates of chlorine () or sulfur dioxide (), and significantly higher than the stability of the hydrate of hydrogen sulfide ().


title: Radon

text: Because of its cost and radioactivity, experimental chemical research is seldom performed with radon, and as a result there are very few reported compounds of radon, all either fluorides or oxides. Radon can be oxidized by powerful oxidizing agents such as fluorine, thus forming radon difluoride (). It decomposes back to its elements at a temperature of above , and is reduced by water to radon gas and hydrogen fluoride: it may also be reduced back to its elements by hydrogen gas. It has a low volatility and was thought to be . Because of the short half-life of radon and the radioactivity of its compounds, it has not been possible to study the compound in any detail. Theoretical studies on this molecule predict that it should have a Rn–F bond distance of 2.08 ångström (Å), and that the compound is thermodynamically more stable and less volatile than its lighter counterpart xenon difluoride (). The octahedral molecule was predicted to have an even lower enthalpy of formation than the difluoride. The [RnF] ion is believed to form by the following reaction:


title: Radon

text: For this reason, antimony pentafluoride together with chlorine trifluoride and have been considered for radon gas removal in uranium mines due to the formation of radon–fluorine compounds. Radon compounds can be formed by the decay of radium in radium halides, a reaction that has been used to reduce the amount of radon that escapes from targets during irradiation. Additionally, salts of the [RnF] cation with the anions , , and are known. Radon is also oxidised by dioxygen difluoride to at .


title: Radon

text: Radon oxides are among the few other reported ; only the trioxide () has been confirmed. The higher fluorides and have been claimed and are calculated to be stable, but their identification is unclear. They may have been observed in experiments where unknown radon-containing products distilled together with xenon hexafluoride: these may have been , , or both. Trace-scale heating of radon with xenon, fluorine, bromine pentafluoride, and either sodium fluoride or nickel fluoride was claimed to produce a higher fluoride as well which hydrolysed to form . While it has been suggested that these claims were really due to radon precipitating out as the solid complex [RnF][NiF], the fact that radon coprecipitates from aqueous solution with has been taken as confirmation that was formed, which has been supported by further studies of the hydrolysed solution. That [RnOF] did not form in other experiments may have been due to the high concentration of fluoride used. Electromigration studies also suggest the presence of cationic [HRnO] and anionic [HRnO] forms of radon in weakly acidic aqueous solution (pH > 5), the procedure having previously been validated by examination of the homologous xenon trioxide.


title: Radon

text: The decay technique has also been used. Avrorin et al. reported in 1982 that Fr compounds cocrystallised with their caesium analogues appeared to retain chemically bound radon after electron capture; analogies with xenon suggested the formation of RnO, but this could not be confirmed.


title: Radon

text: It is likely that the difficulty in identifying higher fluorides of radon stems from radon being kinetically hindered from being oxidised beyond the divalent state because of the strong ionicity of radon difluoride () and the high positive charge on radon in RnF; spatial separation of molecules may be necessary to clearly identify higher fluorides of radon, of which is expected to be more stable than due to spin–orbit splitting of the 6p shell of radon (Rn would have a closed-shell 6s6p configuration). Therefore, while should have a similar stability to xenon tetrafluoride (), would likely be much less stable than xenon hexafluoride (): radon hexafluoride would also probably be a regular octahedral molecule, unlike the distorted octahedral structure of , because of the inert pair effect. Because radon is quite electropositive for a noble gas, it is possible that radon fluorides actually take on highly fluorine-bridged structures and are not volatile. Extrapolation down the noble gas group would suggest also the possible existence of RnO, RnO, and RnOF, as well as the first chemically stable noble gas chlorides RnCl and RnCl, but none of these have yet been found.


title: Radon

text: Radon carbonyl (RnCO) has been predicted to be stable and to have a linear molecular geometry. The molecules and RnXe were found to be significantly stabilized by spin-orbit coupling. Radon caged inside a fullerene has been proposed as a drug for tumors. Despite the existence of Xe(VIII), no Rn(VIII) compounds have been claimed to exist; should be highly unstable chemically (XeF is thermodynamically unstable). It is predicted that the most stable Rn(VIII) compound would be barium perradonate (BaRnO), analogous to barium perxenate. The instability of Rn(VIII) is due to the relativistic stabilization of the 6s shell, also known as the inert pair effect.


title: Radon

text: Radon reacts with the liquid halogen fluorides ClF, , , , , and to form . In halogen fluoride solution, radon is nonvolatile and exists as the RnF and Rn cations; addition of fluoride anions results in the formation of the complexes and , paralleling the chemistry of beryllium(II) and aluminium(III). The standard electrode potential of the Rn/Rn couple has been estimated as +2.0 V, although there is no evidence for the formation of stable radon ions or compounds in aqueous solution.


title: Radon

text: Radon has no stable isotopes. Thirty-nine radioactive isotopes have been characterized, with atomic masses ranging from 193 to 231. The most stable isotope is Rn, which is a decay product of Ra, a decay product of U. A trace amount of the (highly unstable) isotope Rn is also among the daughters of Rn.


title: Radon

text: Three other radon isotopes have a half-life of over an hour: Rn, Rn and Rn. The Rn isotope is a natural decay product of the most stable thorium isotope (Th), and is commonly referred to as thoron. It has a half-life of 55.6 seconds and also emits alpha radiation. Similarly, Rn is derived from the most stable isotope of actinium (Ac)—named "actinon"—and is an alpha emitter with a half-life of 3.96 seconds. No radon isotopes occur significantly in the neptunium (Np) decay series, though a trace amount of the (extremely unstable) isotope Rn is produced.


title: Radon

text: Rn belongs to the radium and uranium-238 decay chain, and has a half-life of 3.8235 days. Its first four products (excluding marginal decay schemes) are very short-lived, meaning that the corresponding disintegrations are indicative of the initial radon distribution. Its decay goes through the following sequence:


title: Radon

text: The radon equilibrium factor is the ratio between the activity of all short-period radon progenies (which are responsible for most of radon's biological effects), and the activity that would be at equilibrium with the radon parent.


title: Radon

text: If a closed volume is constantly supplied with radon, the concentration of short-lived isotopes will increase until an equilibrium is reached where the rate of decay of each decay product will equal that of the radon itself. The equilibrium factor is 1 when both activities are equal, meaning that the decay products have stayed close to the radon parent long enough for the equilibrium to be reached, within a couple of hours. Under these conditions, each additional pCi/L of radon will increase exposure by 0.01 "working level" (WL, a measure of radioactivity commonly used in mining). These conditions are not always met; in many homes, the equilibrium factor is typically 40%; that is, there will be 0.004 WL of daughters for each pCi/L of radon in the air. Pb takes much longer (decades) to come in equilibrium with radon, but, if the environment permits accumulation of dust over extended periods of time, Pb and its decay products may contribute to overall radiation levels as well.


title: Radon

text: Because of their electrostatic charge, radon progenies adhere to surfaces or dust particles, whereas gaseous radon does not. Attachment removes them from the air, usually causing the equilibrium factor in the atmosphere to be less than 1. The equilibrium factor is also lowered by air circulation or air filtration devices, and is increased by airborne dust particles, including cigarette smoke. The equilibrium factor found in epidemiological studies is 0.4.


title: Radon

text: Radon was the fifth radioactive element to be discovered, in 1899 by Ernest Rutherford and Robert B. Owens at McGill University in Montreal, after uranium, thorium, radium, and polonium. In 1899, Pierre and Marie Curie observed that the gas emitted by radium remained radioactive for a month. Later that year, Rutherford and Owens noticed variations when trying to measure radiation from thorium oxide. Rutherford noticed that the compounds of thorium continuously emit a radioactive gas that remains radioactive for several minutes, and called this gas "emanation" (from , to flow out, and , expiration), and later "thorium emanation" ("Th Em"). In 1900, Friedrich Ernst Dorn reported some experiments in which he noticed that radium compounds emanate a radioactive gas he named "radium emanation" ("Ra Em"). In 1901, Rutherford and Harriet Brooks demonstrated that the emanations are radioactive, but credited the Curies for the discovery of the element. In 1903, similar emanations were observed from actinium by André-Louis Debierne, and were called "actinium emanation" ("Ac Em").


title: Radon

text: Several shortened names were soon suggested for the three emanations: "exradio", "exthorio", and "exactinio" in 1904; "radon" (Ro), "thoron" (To), and "akton" or "acton" (Ao) in 1918; "radeon", "thoreon", and "actineon" in 1919, and eventually "radon", "thoron", and "actinon" in 1920. (The name radon is not related to that of the Austrian mathematician Johann Radon.) The likeness of the spectra of these three gases with those of argon, krypton, and xenon, and their observed chemical inertia led Sir William Ramsay to suggest in 1904 that the "emanations" might contain a new element of the noble-gas family.


title: Radon

text: In the early 20th century in the US, gold contaminated with the radon daughter Pb entered the jewelry industry. This was from gold seeds that had held Rn that had been melted down after the radon had decayed.


title: Radon

text: In 1909, Ramsay and Robert Whytlaw-Gray isolated radon and determined its melting temperature and approximate density. In 1910, they determined that it was the heaviest known gas. They wrote that "" ("the expression 'radium emanation' is very awkward") and suggested the new name niton (Nt) (from , shining) to emphasize the radioluminescence property, and in 1912 it was accepted by the International Commission for Atomic Weights. In 1923, the International Committee for Chemical Elements and International Union of Pure and Applied Chemistry (IUPAC) chose among the names radon (Rn), thoron (Tn), and actinon (An). Later, when isotopes were numbered instead of named, the element took the name of the most stable isotope, "radon", while Tn was renamed Rn and An was renamed Rn. This has caused some confusion in the literature regarding the element's discovery as while Dorn had discovered radon the isotope, he had not been the first to discover radon the element.


title: Radon

text: As late as the 1960s, the element was also referred to simply as "emanation". The first synthesized compound of radon, radon fluoride, was obtained in 1962. Even today, the word "radon" may refer to either the element or its isotope Rn, with "thoron" remaining in use as a short name for Rn to stem this ambiguity. The name "actinon" for Rn is rarely encountered today, probably due to the short half-life of that isotope.


title: Radon

text: The danger of high exposure to radon in mines, where exposures can reach 1,000,000 Bq/m, has long been known. In 1530, Paracelsus described a wasting disease of miners, the "mala metallorum", and Georg Agricola recommended ventilation in mines to avoid this mountain sickness ("Bergsucht"). In 1879, this condition was identified as lung cancer by Harting and Hesse in their investigation of miners from Schneeberg, Germany. The first major studies with radon and health occurred in the context of uranium mining in the Joachimsthal region of Bohemia. In the US, studies and mitigation only followed decades of health effects on uranium miners of the Southwestern US employed during the early Cold War; standards were not implemented until 1971.


title: Radon

text: The presence of radon in indoor air was documented as early as 1950. Beginning in the 1970s, research was initiated to address sources of indoor radon, determinants of concentration, health effects, and mitigation approaches. In the US, the problem of indoor radon received widespread publicity and intensified investigation after a widely publicized incident in 1984. During routine monitoring at a Pennsylvania nuclear power plant, a worker was found to be contaminated with radioactivity. A high concentration of radon in his home was subsequently identified as responsible.


title: Radon

text: All discussions of radon concentrations in the environment refer to Rn. While the average rate of production of Rn (from the thorium decay series) is about the same as that of Rn, the amount of Rn in the environment is much less than that of Rn because of the short half-life of Rn (55 seconds, versus 3.8 days respectively).


title: Radon

text: Radon concentration in the atmosphere is usually measured in becquerel per cubic meter (Bq/m), the SI derived unit. Another unit of measurement common in the US is picocuries per liter (pCi/L); 1 pCi/L = 37 Bq/m. Typical domestic exposures average about 48 Bq/m indoors, though this varies widely, and 15 Bq/m outdoors.


title: Radon

text: In the mining industry, the exposure is traditionally measured in "working level" (WL), and the cumulative exposure in "working level month" (WLM); 1 WL equals any combination of short-lived Rn daughters (Po, Pb, Bi, and Po) in 1 liter of air that releases 1.3 × 10 MeV of potential alpha energy; 1 WL is equivalent to 2.08 × 10 joules per cubic meter of air (J/m). The SI unit of cumulative exposure is expressed in joule-hours per cubic meter (J·h/m). One WLM is equivalent to 3.6 × 10 J·h/m. An exposure to 1 WL for 1 working-month (170 hours) equals 1 WLM cumulative exposure. A cumulative exposure of 1 WLM is roughly equivalent to living one year in an atmosphere with a radon concentration of 230 Bq/m.


title: Radon

text: Rn decays to Pb and other radioisotopes. The levels of Pb can be measured. The rate of deposition of this radioisotope is weather-dependent.


title: Radon

text: Radon concentrations found in natural environments are much too low to be detected by chemical means. A 1,000 Bq/m (relatively high) concentration corresponds to 0.17 picogram per cubic meter (pg/m). The average concentration of radon in the atmosphere is about 6 molar percent, or about 150 atoms in each milliliter of air. The radon activity of the entire Earth's atmosphere originates from only a few tens of grams of radon, consistently replaced by decay of larger amounts of radium, thorium, and uranium.


title: Radon

text: Radon is produced by the radioactive decay of radium-226, which is found in uranium ores, phosphate rock, shales, igneous and metamorphic rocks such as granite, gneiss, and schist, and to a lesser degree, in common rocks such as limestone. Every square mile of surface soil, to a depth of 6 inches (2.6 km to a depth of 15 cm), contains approximately 1 gram of radium, which releases radon in small amounts to the atmosphere. On a global scale, it is estimated that 2.4 billion curies (90 EBq) of radon are released from soil annually. This is equivalent to some .


title: Radon

text: Radon concentration can differ widely from place to place. In the open air, it ranges from 1 to 100 Bq/m, even less (0.1 Bq/m) above the ocean. In caves or ventilated mines, or poorly ventilated houses, its concentration climbs to 20–2,000 Bq/m.


title: Radon

text: Radon concentration can be much higher in mining contexts. Ventilation regulations instruct to maintain radon concentration in uranium mines under the "working level", with 95th percentile levels ranging up to nearly 3 WL (546 pCi Rn per liter of air; 20.2 kBq/m, measured from 1976 to 1985).


title: Radon

text: The concentration in the air at the (unventilated) Gastein Healing Gallery averages 43 kBq/m (1.2 nCi/L) with maximal value of 160 kBq/m (4.3 nCi/L).


title: Radon

text: Radon mostly appears with the decay chain of the radium and uranium series (Rn), and marginally with the thorium series (Rn). The element emanates naturally from the ground, and some building materials, all over the world, wherever traces of uranium or thorium are found, and particularly in regions with soils containing granite or shale, which have a higher concentration of uranium. Not all granitic regions are prone to high emissions of radon. Being a rare gas, it usually migrates freely through faults and fragmented soils, and may accumulate in caves or water. Owing to its very short half-life (four days for Rn), radon concentration decreases very quickly when the distance from the production area increases. Radon concentration varies greatly with season and atmospheric conditions. For instance, it has been shown to accumulate in the air if there is a meteorological inversion and little wind.


title: Radon

text: High concentrations of radon can be found in some spring waters and hot springs. The towns of Boulder, Montana; Misasa; Bad Kreuznach, Germany; and the country of Japan have radium-rich springs that emit radon. To be classified as a radon mineral water, radon concentration must be above 2 nCi/L (74 kBq/m). The activity of radon mineral water reaches 2,000 kBq/m in Merano and 4,000 kBq/m in Lurisia (Italy).


title: Radon

text: Natural radon concentrations in the Earth's atmosphere are so low that radon-rich water in contact with the atmosphere will continually lose radon by volatilization. Hence, ground water has a higher concentration of Rn than surface water, because radon is continuously produced by radioactive decay of Ra present in rocks. Likewise, the saturated zone of a soil frequently has a higher radon content than the unsaturated zone because of diffusional losses to the atmosphere.


title: Radon

text: In 1971, Apollo 15 passed above the Aristarchus plateau on the Moon, and detected a significant rise in alpha particles thought to be caused by the decay of Rn. The presence of Rn has been inferred later from data obtained from the Lunar Prospector alpha particle spectrometer.


title: Radon

text: Radon is found in some petroleum. Because radon has a similar pressure and temperature curve to propane, and oil refineries separate petrochemicals based on their boiling points, the piping carrying freshly separated propane in oil refineries can become contaminated because of decaying radon and its products.


title: Radon

text: Residues from the petroleum and natural gas industry often contain radium and its daughters. The sulfate scale from an oil well can be radium rich, while the water, oil, and gas from a well often contains radon. Radon decays to form solid radioisotopes that form coatings on the inside of pipework.


title: Radon

text: High concentrations of radon in homes were discovered by chance in 1985 after the stringent radiation testing conducted at the new Limerick Generating Station nuclear power plant revealed that Stanley Watras, a construction engineer at the plant, was contaminated by radioactive substances even though the reactor had never been fueled. Typical domestic exposures are of approximately 100 Bq/m (2.7 pCi/L) indoors. Some level of radon will be found in all buildings. Radon mostly enters a building directly from the soil through the lowest level in the building that is in contact with the ground. High levels of radon in the water supply can also increase indoor radon air levels. Typical entry points of radon into buildings are cracks in solid foundations and walls, construction joints, gaps in suspended floors and around service pipes, cavities inside walls, and the water supply. Radon concentrations in the same place may differ by double/half over one hour. Also, the concentration in one room of a building may be significantly different from the concentration in an adjoining room. The soil characteristics of the dwellings are the most important source of radon for the ground floor and higher concentration of indoor radon observed on lower floors. Most of the high radon concentrations have been reported from places near fault zones; hence the existence of a relation between the exhalation rate from faults and indoor radon concentrations is obvious.


title: Radon

text: The distribution of radon concentrations will generally differ from room to room, and the readings are averaged according to regulatory protocols. Indoor radon concentration is usually assumed to follow a log-normal distribution on a given territory. Thus, the geometric mean is generally used for estimating the "average" radon concentration in an area.


title: Radon

text: The mean concentration ranges from less than 10 Bq/m to over 100 Bq/m in some European countries. Typical geometric standard deviations found in studies range between 2 and 3, meaning (given the 68–95–99.7 rule) that the radon concentration is expected to be more than a hundred times the mean concentration for 2% to 3% of the cases.


title: Radon

text: Some of the highest radon hazard in the US is found in Iowa and in the Appalachian Mountain areas in southeastern Pennsylvania. Iowa has the highest average radon concentrations in the US due to significant glaciation that ground the granitic rocks from the Canadian Shield and deposited it as soils making up the rich Iowa farmland. Many cities within the state, such as Iowa City, have passed requirements for radon-resistant construction in new homes. The second highest readings in Ireland were found in office buildings in the Irish town of Mallow, County Cork, prompting local fears regarding lung cancer.


title: Radon

text: In a few places, uranium tailings have been used for landfills and were subsequently built upon, resulting in possible increased exposure to radon.


title: Radon

text: Since radon is a colorless, odorless gas, the only way to know how much is present in the air or water is to perform tests. In the US, radon test kits are available to the public at retail stores, such as hardware stores, for home use, and testing is available through licensed professionals, who are often home inspectors. Efforts to reduce indoor radon levels are called radon mitigation. In the US, the EPA recommends all houses be tested for radon. In the UK under the Housing Health & Safety Rating System (HHSRS) property owners have an obligation to evaluate potential risks and hazards to health and safety in a residential property.


title: Radon

text: Radon is obtained as a by-product of uraniferous ores processing after transferring into 1% solutions of hydrochloric or hydrobromic acids. The gas mixture extracted from the solutions contains , , He, Rn, , and hydrocarbons. The mixture is purified by passing it over copper at to remove the and the , and then KOH and are used to remove the acids and moisture by sorption. Radon is condensed by liquid nitrogen and purified from residue gases by sublimation.


title: Radon

text: Radon commercialization is regulated, but it is available in small quantities for the calibration of Rn measurement systems, at a price, in 2008, of almost per milliliter of radium solution (which only contains about 15 picograms of actual radon at any given moment).


title: Radon

text: Radon is produced by a solution of radium-226 (half-life of 1,600 years). Radium-226 decays by alpha-particle emission, producing radon that collects over samples of radium-226 at a rate of about 1 mm/day per gram of radium; equilibrium is quickly achieved and radon is produced in a steady flow, with an activity equal to that of the radium (50 Bq). Gaseous Rn (half-life of about four days) escapes from the capsule through diffusion.


title: Radon

text: An early-20th-century form of quackery was the treatment of maladies in a radiotorium. It was a small, sealed room for patients to be exposed to radon for its "medicinal effects". The carcinogenic nature of radon due to its ionizing radiation became apparent later. Radon's molecule-damaging radioactivity has been used to kill cancerous cells, but it does not increase the health of healthy cells. The ionizing radiation causes the formation of free radicals, which results in cell damage, causing increased rates of illness, including cancer.


title: Radon

text: Exposure to radon has been suggested to mitigate autoimmune diseases such as arthritis in a process known as radiation hormesis. As a result, in the late 20th century and early 21st century, "health mines" established in Basin, Montana, attracted people seeking relief from health problems such as arthritis through limited exposure to radioactive mine water and radon. The practice is discouraged because of the well-documented ill effects of high doses of radiation on the body.


title: Radon

text: Radioactive water baths have been applied since 1906 in Jáchymov, Czech Republic, but even before radon discovery they were used in Bad Gastein, Austria. Radium-rich springs are also used in traditional Japanese onsen in Misasa, Tottori Prefecture. Drinking therapy is applied in Bad Brambach, Germany, and during the early 20th century, water from springs with radon in them was bottled and sold (this water had little to no radon in it by the time it got to consumers due to radon's short half-life). Inhalation therapy is carried out in Gasteiner-Heilstollen, Austria, in Świeradów-Zdrój, Czerniawa-Zdrój, Kowary, Lądek Zdrój, Poland, in Harghita Băi, Romania, and in Boulder, Montana. In the US and Europe, there are several "radon spas", where people sit for minutes or hours in a high-radon atmosphere.


title: Radon

text: Radon has been produced commercially for use in radiation therapy, but for the most part has been replaced by radionuclides made in particle accelerators and nuclear reactors. Radon has been used in implantable seeds, made of gold or glass, primarily used to treat cancers, known as brachytherapy.


title: Radon

text: The gold seeds were produced by filling a long tube with radon pumped from a radium source, the tube being then divided into short sections by crimping and cutting. The gold layer keeps the radon within, and filters out the alpha and beta radiations, while allowing the gamma rays to escape (which kill the diseased tissue). The activities might range from 0.05 to 5 millicuries per seed (2 to 200 MBq). The gamma rays are produced by radon and the first short-lived elements of its decay chain (Po, Pb, Bi, Po).


title: Radon

text: Radon and its first decay products being very short-lived, the seed is left in place. After 11 half-lives (42 days), radon radioactivity is at 1/2,048 of its original level. At this stage, the predominant residual activity originates from the radon decay product Pb, whose half-life (22.3 years) is 2,000 times that of radon and its descendants Bi and Po.


title: Radon

text: Radon emanation from the soil varies with soil type and with surface uranium content, so outdoor radon concentrations can be used to track air masses to a limited degree. This fact has been put to use by some atmospheric scientists (Radon storm). Because of radon's rapid loss to air and comparatively rapid decay, radon is used in hydrologic research that studies the interaction between groundwater and streams. Any significant concentration of radon in a stream is a good indicator that there are local inputs of groundwater.


title: Radon

text: Radon soil-concentration has been used in an experimental way to map buried close-subsurface geological faults because concentrations are generally higher over the faults. Similarly, it has found some limited use in prospecting for geothermal gradients.


title: Radon

text: Some researchers have investigated changes in groundwater radon concentrations for earthquake prediction. Increases in radon were noted before the 1966 Tashkent and 1994 Mindoro earthquakes. Radon has a half-life of approximately 3.8 days, which means that it can be found only shortly after it has been produced in the radioactive decay chain. For this reason, it has been hypothesized that increases in radon concentration is due to the generation of new cracks underground, which would allow increased groundwater circulation, flushing out radon. The generation of new cracks might not unreasonably be assumed to precede major earthquakes. In the 1970s and 1980s, scientific measurements of radon emissions near faults found that earthquakes often occurred with no radon signal, and radon was often detected with no earthquake to follow. It was then dismissed by many as an unreliable indicator. As of 2009, it was under investigation as a possible precursor by NASA.


title: Radon

text: Radon is a known pollutant emitted from geothermal power stations because it is present in the material pumped from deep underground. It disperses rapidly, and no radiological hazard has been demonstrated in various investigations. In addition, typical systems re-inject the material deep underground rather than releasing it at the surface, so its environmental impact is minimal. However, similar things can be said about trivial releases from operating nuclear power plants.


title: Radon

text: In the 1940s and '50s, radon was used for industrial radiography. Other X-ray sources, which became available after World War II, quickly replaced radon for this application, as they were lower in cost and had less hazard of alpha radiation.


title: Radon

text: Radon-222 decay products have been classified by the International Agency for Research on Cancer as being carcinogenic to humans, and as a gas that can be inhaled, lung cancer is a particular concern for people exposed to elevated levels of radon for sustained periods. During the 1940s and 1950s, when safety standards requiring expensive ventilation in mines were not widely implemented, radon exposure was linked to lung cancer among non-smoking miners of uranium and other hard rock materials in what is now the Czech Republic, and later among miners from the Southwestern US and South Australia. Despite these hazards being known in the early 1950s, this occupational hazard remained poorly managed in many mines until the 1970s. During this period, several entrepreneurs opened former uranium mines in the US to the general public and advertised alleged health benefits from breathing radon gas underground. Health benefits claimed included pain, sinus, asthma and arthritis relief, but these were proven to be false and the government banned such advertisements in 1975.


title: Radon

text: Since that time, ventilation and other measures have been used to reduce radon levels in most affected mines that continue to operate. In recent years, the average annual exposure of uranium miners has fallen to levels similar to the concentrations inhaled in some homes. This has reduced the risk of occupationally-induced cancer from radon, although health issues may persist for those who are currently employed in affected mines and for those who have been employed in them in the past. As the relative risk for miners has decreased, so has the ability to detect excess risks among that population.


title: Radon

text: Residues from processing of uranium ore can also be a source of radon. Radon resulting from the high radium content in uncovered dumps and tailing ponds can be easily released into the atmosphere and affect people living in the vicinity.


title: Radon

text: In addition to lung cancer, researchers have theorized a possible increased risk of leukemia due to radon exposure. Empirical support from studies of the general population is inconsistent, and a study of uranium miners found a correlation between radon exposure and chronic lymphocytic leukemia.


title: Radon

text: Miners (as well as milling and ore transportation workers) who worked in the uranium industry in the US between the 1940s and 1971 may be eligible for compensation under the Radiation Exposure Compensation Act (RECA). Surviving relatives may also apply in cases where the formerly employed person is deceased.


title: Radon

text: Not only uranium mines are affected by elevated levels of radon. Coal mines in particular are affected as well since coal may contain more uranium and thorium than commercially operational uranium mines.