the 1950s the chemical defence experimental establishment became involved with the development of cs, a riot control agent, and took an increasing role in trauma and wound ballistics work. both these facets of porton down's work had become more important because of the situation in northern ireland. in the early 1950s, nerve agents such as sarin were produced— about 20 tons were made from 1954 until 1956. cde nancekuke was an important factory for stockpiling chemical weapons. small amounts of vx were produced there, mainly for laboratory test purposes, but also to validate plant designs and optimise chemical processes for potential mass production. however, full-scale mass production of vx agent never took place, with the 1956 decision to end the uk's offensive chemical weapons programme. in the late 1950s, the chemical weapons production plant at nancekuke was mothballed, but was maintained through the 1960s and 1970s in a state whereby production of chemical weapons could easily re-commence if required. united states in 1952, the u.s. army patented a process for the "preparation of toxic ricin", publishing a method of producing this powerful toxin. in 1958 the british government traded their vx technology with the united states in exchange for information on thermonuclear weapons. by 1961 the u.s. was producing large amounts of vx and performing its own nerve agent research. this research produced at least three more agents; the four agents (ve, vg, vm, vx) are collectively known as the "v-series" class of nerve agents. between 1951 and 1969, dugway proving ground was the site of testing for various chemical and biological agents, including an open-air aerodynamic dissemination test in 1968 that accidentally killed, on neighboring farms, approximately 6,400 sheep by an unspecified nerve agent. from 1962 to 1973, the department of defense planned 134 tests under project 112, a chemical and biological weapons "vulnerability-testing program." in 2002, the pentagon admitted for the first time that some of tests used real chemical and biological weapons, not just harmless simulants. specifically under project shad, 37 secret tests were conducted in california, alaska, florida, hawaii, maryland and utah. land tests in alaska and hawaii used artillery shells filled with sarin and vx, while navy trials off the coasts of florida, california and hawaii tested the ability of ships and crew to perform under biological and chemical warfare, without the crew's knowledge. the code name for the sea tests was project shipboard hazard and defense—"shad" for short. in october 2002, the senate armed forces subcommittee on personnel held hearings as the controversial news broke that chemical agents had been tested on thousands of american military personnel. the hearings were chaired by senator max cleland, former va administrator and vietnam war veteran. united states chemical respiratory protection standardization in december 2001, the united states department of health and human services, centers for disease control and prevention (cdc), national institute for occupational safety and health (niosh), and national personal protective technology laboratory (npptl), along with the u.s. army research, development and engineering command (rdecom), edgewood chemical and biological center (ecbc), and the u.s. department of commerce national institute of standards and technology (nist) published the first of six technical performance standards and test procedures designed to evaluate and certify respirators intended for use by civilian emergency responders to a chemical, biological, radiological, or nuclear weapon release, detonation, or terrorism incident. to date niosh/npptl has published six new respirator performance standards based on a tiered approach that relies on traditional industrial respirator certification policy, next-generation emergency response respirator performance requirements, and special live chemical warfare agent testing requirements of the classes of respirators identified to offer respiratory protection against chemical, biological, radiological, and nuclear (cbrn) agent inhalation hazards. these cbrn respirators are commonly known as open-circuit self-contained breathing apparatus (cbrn scba), air-purifying respirator (cbrn apr), air-purifying escape respirator (cbrn aper), self-contained escape respirator (cbrn scer) and loose- or tight-fitting powered air-purifying respirators (cbrn papr). soviet union due to the secrecy of the soviet union's government, very little information was available about the direction and progress of the soviet chemical weapons until relatively recently. after the fall of the soviet union, russian chemist vil mirzayanov published articles revealing illegal chemical weapons experimentation in russia. in 1993, mirzayanov was imprisoned and fired from his job at the state research institute of organic chemistry and technology, where he had worked for 26 years. in march 1994, after a major campaign by u.s. scientists on his behalf, mirzayanov was released. among the information related by vil mirzayanov was the direction of soviet research into the development of even more toxic nerve agents, which saw most of its success during the mid-1980s. several highly toxic agents were developed during this period; the only unclassified information regarding these agents is that they are known in the open literature only as "foliant" agents (named after the program under which they were developed) and by various code designations, such as a-230 and a-232. according to mirzayanov, the soviets also developed weapons that were safer to handle, leading to the development of binary weapons, in which precursors for the nerve agents are mixed in a munition to produce the agent just prior to its use. because the precursors are generally significantly less hazardous than the agents themselves, this technique makes handling and transporting the munitions a great deal simpler. additionally, precursors to the agents are usually much easier to stabilize than the agents themselves, so this technique also made it possible to increase the shelf life of the agents a great deal. during the 1980s and 1990s, binary versions of several soviet agents were developed and designated "novichok" agents (after the russian word for "newcomer"). together with lev fedorov, he told the secret novichok story exposed in the newspaper the moscow news. use in conflicts after world war ii north yemen the international red cross hospital at uqd, north yemen, where the use of chemical weapons was alleged to have occurred the first attack of the north yemen civil war took place on june 8, 1963 against kawma, a village of about 100 inhabitants in northern yemen, killing about seven people and damaging the eyes and lungs of 25 others. this incident is considered to have been experimental, and the bombs were described as "home-made, amateurish and relatively ineffective". the egyptian authorities suggested that the reported incidents were probably caused by napalm, not gas. there were no reports of gas during 1964, and only a few were reported in 1965. the reports grew more frequent in late 1966. on december 11, 1966, fifteen gas bombs killed two people and injured thirty-five. on january 5, 1967, the biggest gas attack came against the village of kitaf, causing 270 casualties, including 140 fatalities. the target may have been prince hassan bin yahya, who had installed his headquarters nearby. the egyptian government denied using poison gas, and alleged that britain and the us were using the reports as psychological warfare against egypt. on february 12, 1967, it said it would welcome a un investigation. on march 1, u thant, the then secretary-general of the united nations, said he was "powerless" to deal with the matter. on may 10, 1967 the twin villages of gahar and gadafa in wadi hirran, where prince mohamed bin mohsin was in command, were gas bombed, killing at least seventy-five. the red cross was alerted and on june 2, 1967, it issued a statement in geneva expressing concern. the institute of forensic medicine at the university of berne made a statement, based on a red cross report, that the gas was likely to have been halogenous derivatives—phosgene, mustard gas, lewisite, chloride or cyanogen bromide. rhodesian bush war evidence points to a top-secret rhodesian program in the 1970s to use organophosphate pesticides and heavy metal rodenticides to contaminate clothing as well as food and beverages. the contaminated items were covertly introduced into insurgent supply chains. hundreds of insurgent deaths were reported, although the actual death toll likely rose over 1,000. angola during the cuban intervention in angola, united nations toxicologists certified that residue from both vx and sarin nerve agents had been discovered in plants, water, and soil where cuban units were conducting operations against national union for the total independence of angola (unita) insurgents. in 1985, unita made the first of several claims that their forces were the target of chemical weapons, specifically organophosphates. the following year guerrillas reported being bombarded with an unidentified greenish-yellow agent on three separate occasions. depending on the length and intensity of exposure, victims suffered blindness or death. the toxin was also observed to have killed plant life. shortly afterwards, unita also sighted strikes carried out with a brown agent which it claimed resembled mustard gas. as early as 1984 a research team dispatched by the university of ghent had examined patients in unita field hospitals showing signs of exposure to nerve agents, although it found no evidence of mustard gas. the un first accused cuba of deploying chemical weapons against angolan civilians and partisans in 1988. wouter basson later disclosed that south african military intelligence had long verified the use of unidentified chemical weapons on angolan soil; this was to provide the impetus for their own biological warfare programme, project coast. during the battle of cuito cuanavale, south african troops then fighting in angola were issued with gas masks and ordered to rehearse chemical weapons drills. although the status of its own chemical weapons program remained uncertain, south africa also deceptively bombarded cuban and angolan units with colored smoke in an attempt to induce hysteria or mass panic. according to defence minister magnus malan, this would force the cubans to share the inconvenience of having to take preventative measures such as donning nbc suits, which would cut combat effectiveness in half. the tactic was effective: beginning in early 1988 cuban units posted to angola were issued with full protective gear in anticipation of a south african chemical strike. on october 29, 1988, personnel attached to angola's 59 brigade, accompanied by six soviet military advisors, reported being struck with chemical weapons on the banks of the mianei river. the attack occurred shortly after one in the afternoon. four angolan soldiers lost consciousness while the others complained of violent headaches and nausea. that november the angolan representative to the un accused south africa of employing poison gas near cuito cuanavale for the first time. falklands war technically, the reported employment of tear gas by argentine forces during the 1982 invasion of the falkland islands constitutes chemical warfare. however, the tear gas grenades were employed as nonlethal weapons to avoid british casualties. the barrack buildings the weapons were used on proved to be deserted in any case. the british claim that more lethal, but legally justifiable as they are not considered chemical weapons under the chemical weapons convention, white phosphorus grenades were used. afghanistan there were reports of chemical weapons being used by soviet forces during the soviet–afghan war, sometimes against civilians. vietnamese border raids in thailand there is some evidence suggesting that vietnamese troops used phosgene gas against cambodian resistance forces in thailand during the 1984–1985 dry-season offensive on the thai-cambodian border. iran–iraq war victims of the 1987 chemical attack on sardasht, west azerbaijan, iran chemical weapons employed by saddam hussein killed and injured numerous iranians and iraqi kurds. according to iraqi documents, assistance in developing chemical weapons was obtained from firms in many countries, including the united states, west germany, the netherlands, the united kingdom, and france. about 100,000 iranian soldiers were victims of iraq's chemical attacks. many were hit by mustard gas. the official estimate does not include the civilian population contaminated in bordering towns or the children and relatives of veterans, many of whom have developed blood, lung and skin complications, according to the organization for veterans. nerve gas agents killed about 20,000 iranian soldiers immediately, according to official reports. of the 80,000 survivors, some 5,000 seek medical treatment regularly and about 1,000 are still hospitalized with severe, chronic conditions. according to the foreign policy, the "iraqis used mustard gas and sarin prior to four major offensives in early 1988 that relied on u.s. satellite imagery, maps, and other intelligence. ... according to recently declassified cia documents and interviews with former intelligence officials like francona, the u.s. had firm evidence of iraqi chemical attacks beginning