|Description and Property Data||Detection||Symptoms and Effects|
|Medical Countermeasures||Physical Countermeasures||Decontamination|
|Common Precursors||Comments and Historical Notes||ICD Codes|
CHEMICAL PROTECTIVE ENSEMBLES ARE REQUIRED FOR PROTECTION!|
Masks, including self-contained breathing apparatus (SCBA) masks, alone do not
provide adequate protection against this agent.
Evacuate upwind without moving through the agent cloud.
|CA Index Name||Hydrocyanic acid|
|CAS Registry Number||74-90-8||RTECS Number||MW6825000|
Hydrogen cyanide is colorless to pale blue when in liquid form, and rapidly evaporates to form a colorless gas. The vapor has an odor that has been described as that of bitter almonds or marzipan; however, a significant fraction of the population is unable to detect this.
CHEMICAL AND PHYSICAL PROPERTIES
| 620 mm Hg at 20°
256 mm Hg at 0°
165 mm Hg at -10°
1,080,000 mg/m3 at 25°
37,000 mg/m3 at -40°
Flammable; Flash Point -18°
Autoignition Temperature 538°
|a The vapor
density relative to air of hydrogen cyanide increases with
At 25.7°, it is 1.007, or slightly heavier than air.
|USFA Hazard Ratings|
(liquified hydrogen cyanide)
Transport containers for hydrogen cyanide may be painted with red and white "candy stripes."
Blood agent sensitive chemical agent detectors (e.g., M18A2, M256, M256A1) may be used for detection. The M272 kit detects cyanide in water. Commercial hydrogen cyanide detectors (e.g., gas monitors, Drager tubes, etc.) are also available.
M8 and M9 papers will not detect hydrogen cyanide.
While hydrogen cyanide is an acid, it is only weakly acidic. The use of moistened litmus or pH paper will not provide a reliable indicator of the presence of this agent.
SYMPTOMS AND EFFECTS
Depending on the degree of intoxication, symptoms may include:
|anxiety and/or confusion|
|hyperpnea followed by dyspnea|
|cyanosis (may be absent; may be followed by a pink color in the skin)|
While some texts describe a bright red coloration of the skin in cyanide poisoning, this appears to be only rarely observed in actual practice.
Onset is usually rapid. Effects on inhalation of lethal amounts may be observed within 15 seconds with death occuring in less than 10 minutes. Hydrogen cyanide should be suspected in terrorist incidents involving prompt fatalities, especially when the characteristic symptoms of nerve agent intoxication are absent.
Tests for cyanide in blood and tissues can be confirmatory, but can take more time than is available for diagnosis in high exposures. RBC cyanide levels of 0.5-1.0 mcg/mL indicate at least mild exposure; higher values indicate more significant exposure.
Other useful laboratory findings
Note: carboxyhemoglobin levels are useful in excluding carbon monoxide poisoning in situations where smoke inhalation has occurred.
|100 mg/kg (liquid)||percutaneous||humans|
|2400 mg-m-3/15 seconds||inhalation||humans|
|1000 mg-m-3/1 minute||inhalation||humans|
|2000 mg-m-3/10 minutes||inhalation||humans|
|20,000 mg-m-3/10 min||percutaneous||mice|
|50,000 mg-m-3/10 min||percutaneous||cats|
|100,000 mg-m-3/10 min||percutaneous||dogs|
|Useful Drugs||Amyl nitrite||Sodium nitrite||Sodium thiosulfate|
Be aware that effects of this agent may be delayed, especially if the exposure involved skin contact with the agents.
Remove victims from exposure and decontaminate them as rapidly as possible. Areas with good air flow should be selected for triage/prehospital treatment to allow dissipation of vapor from contaminated individuals. Victims should not be moved into clean treatment areas where unmasked/ungloved personnel are working until decontamination is complete.
100% oxygen should be given to all victims of exposure, even those with very mild symptoms.
Cyanide is removed by natural metabolic processes, and if exposure is terminated before it has produced lethal levels in the blood the prognosis for recovery is very good, even without antidotal therapy.
|Endotracheal intubation is indicated for victims who have stopped breathing.|
Antidotal therapy for symptomatic victims should be administered as soon as possible.
1. Administer a methemoglobin forming agent:
Hydroxocobalamin (vitamin B-12) has been used in France as an antidote at a dose of 70 mg/kg (maximum dose 10 g) administered over 30 minutes.
Sodium bicarbonate should be used to control acidosis in severe poisoning.
(small package/leaking container)
in all directions
persons downwind during
|60 m (200 ft)||0.2 km (0.1 mi)||0.5 km (0.3 mi)|
(large package/multiple small packages)
in all directions
persons downwind during
|500 m (1500 ft)||1.7 km (1.0 mi)||3.9 km (2.4 mi)|
Also refer to 2004 Emergency Response Guidebook (ERG2004) Guide 117.
When dealing with victims who have not been decontaminated protective equipment including self-contained breathing equipment or gas masks should be used. Medical personnel treating contaminated victims should avoid direct (skin-to-skin) contact. Latex gloves are not adequate protection. Chemical protective gloves should be used. Casualties should be decontaminated as rapidly as possible (see the section on decontamination). Remove casualties from exposure as rapidly as possible. Casualties must not be moved into clean treatment areas where unmasked/ungloved personnel are working until decontamination is complete.
Liquid hydrogen cyanide on the skin or in the clothing of victims presents a secondary contamination hazard. While victims who have been exposed only to hydrogen cyanide gas will not ordinarily pose a hazard for secondary contamination, it is better to be safe than sorry. Hydrogen cyanide will dissolve readily in water; wet clothing may retain agent even if the exposure was to vapor only.
While liquid hydrogen cyanide is a skin contact hazard, the vapor alone is not usually a skin contact hazard in the open as it is difficult to attain the extremely high concentrations of the vapor required for it to be a contact hazard.
The combustion products produced by burning hydrogen cyanide are less toxic than the agent.
Decontamination of victims is accomplished by removing the victim from the contaminated area, removal of clothing, and removal of any agent present on the skin. While it will be rare to encounter agent on the skin, due to the low boiling point of hydrogen cyanide, any encountered should be promptly removed by blotting followed by rinsing with copious amounts of water. In the absence of liquid agent residues, victims should be washed with copious amounts of water or soap and water. Ambulatory victims and exposed individuals should shower.
Be aware that the solubility of hydrogen cyanide in water means wet clothing which has been exposed to the agent may retain agent and victims wearing wet clothing may be at increased risk of injury from percutaneous absorption of the agent.
Clothing should be washed thoroughly, but can be returned to its owner after this has been done. Shoes contaminated with liquid agent may need to be destroyed, however.
Urgent decontamination can be accomplished using soap and water, collecting the run-off. However, the volatility of hydrogen cyanide means that, provided there are no materials present which the agent will react with and damage, decontamination may be accomplished by simply allowing the agent to evaporate.
This agent is soluble in any proportion in water. Hydrogen cyanide is stable in water.
The human metabolism is capable of dealing with exposures to small quantities of hydrogen cyanide. The primary process in the metabolic detoxification of cyanide is conversion of the cyanide to thiocyanate in a reaction mediated by the enzyme rhodanese. The increase in the Haber product (LCt50) for hydrogen cyanide with exposure time is largely the result of these metabolic processes.
|Effect of Exposure Time on Haber Product|
|0.25 min||2400 mg/m3||660 mg-min/m3|
|1 min||1000 mg/m3||1000 mg-min/m3|
|10 min||200 mg/m3||2000 mg-min/m3|
|15 min||133 mg/m3||4000 mg-min/m3|
Hydrogen cyanide is present in cigarette smoke, with a cigarette providing (depending on type) 10-400 µg (secondary or sidestream smoke from a cigarette will provide a dose of 0.06-108 µg).
Hydrogen cyanide is also commonly generated in structure fires. Cyanide intoxication may be a complication in smoke inhalation.
Amygdalin, found in apple pips, peach, plum, and cherry seeds, and almonds, will produce hydrogen cyanide via an enzyme-catalyzed reaction when these materials are wet, although the amount produced is small enough that it is only dangerous under unusual circumstances. Some foodstuffs (e.g., cabbage, spinach, lima beans, and almonds) contain small amounts of cyanide.
The ability to detect the odor of hydrogen cyanide appears to be linked to sex - it has been found that 18% of men can not smell it as compared to only 5% of women who lack the ability to detect the odor.
Hydrogen cyanide is included in the category of chemical agents known as blood agents. This is a bit of a misnomer, deriving from the early belief that hydrogen cyanide exerted its toxic effects by action in the blood, a belief resulting from the fact that the blood of victims could have a rich red color (similar to that seen for carbon monoxide poisoning). In fact, the major toxic effects of hydrogen cyanide are the result of the reaction of the cyanide group with an enzyme called cytochrome oxidase in the body's cells. This reaction inactivates the enzyme and prevents it from taking part in a series of reactions by means of which oxygen is used in cells. The inability to use oxygen kills the cells and, incidently, keeps them from taking oxygen from the blood, resulting in the bright red venous blood that caused early researchers to assume the agent acted in the blood. There have been several attempts over the years to do away with the blood agent designation (the terms "cyanide agents" and "cyanogen agents" have been suggested as replacements), but the term has proved surprisingly resilent.
Commercial and Industrial Uses
Hydrogen cyanide is sometimes used in fumigation (e.g., of structures, railroad freight cars, and aircraft) to eliminate rodents and/or insects. It is primarily used as a precursor for the production of cyanide salts (e.g., for gold recovery), acetone, adiponitrile (e.g., for nylon synthesis), chelating agents (for water treatment), and a variety of other materials.
Hydrogen cyanide is a major industrial material. Industrial production is carried out at at least 47 facilities with an aggregate production capacity (in 1999) of about 1.6 billion kilograms (3.5 billion pounds). The major production processes are the Andrussow and BMA (Blausäure-Methan-Ammoniak) processes. It is also produced as a byproduct of acrylonitrile synthesis. Another important production process is the Shawinigen process. Most commonly, the production is used at the site where it is produced to avoid the hazards of shipping the material.
Hydrogen cyanide was discovered in 1782 by Carl Scheele, who was investigating the dye Prussian Blue (or Berlin blaue, as it was known in the German-speaking world). Mixing the dye with an acid and heating gave him a flammable gas that dissolved well in water, producing an acidic solution. Logically enough, he called his discovery Berlin Blausäure (Berlin blue acid - chemical nomenclature in 1782 was not as systematic as it has become today). The Berlin was soon dropped, and it became simply Blausäure (in the English-speaking world, the name became Prussic acid). Scheele's death in 1786 is sometimes attributed to accidental poisoning by hydrogen cyanide; it may also have been due to chronic poisoning due to his habit (common among chemists of the time) of tasting everything he synthesized.
The actual composition - 1 atom each of hydrogen, carbon, and nitrogen - of hydrogen cyanide was not definitively determined until 1811 by Joseph-Louis Gay-Lussac. While Claude-Louis Berthollet had analyzed it in 1787 and determined that it contained only hydrogen, carbon, and nitrogen, his results had been questioned because it was manifestly an acid, and the prevailing theory of acids (Lavoisier's oxygen theory of acidity) at the time stated that oxygen had to be present for a material to act as an acid. Gay-Lussac's results for hydrogen cyanide, along with those of Davy for hydrochloric acid, were essential in disproving this theory.
Its poisonous properties led to its early consideration as a chemical warfare agent, but during the First World War, hydrogen cyanide was employed only occasionally, primarily by the French. who dubbed it Forestite. Because of its high vapor pressure and low vapor density it tended to dissipate rapidly, and its low flash point meant that it would often (about half the time) ignite when released from artillery shells, limiting its military effectiveness. The French attempted to produce hydrogen cyanide-containing mixtures that would be more persistent, and so more useful. The best known of these is probably Vincennite, which was a mixture of 50% hydrogen cyanide with the smoke producers arsenic trichloride (30%) and stannic chloride (15%) along with chloroform as a stabilizer. Despite their best efforts, however, they were never able to produce a hydrogen cyanide munition that answered the needs of the period, and in a war in which the chemical industries of the world strained to produce enough deadly chemicals, usage of hydrogen cyanide was a relatively paltry 4000 tons.
The French belief in the utility of hydrogen cyanide as a war gas stemmed in large part from experiments done on inhalation exposure in dogs. There was considerable disagreement in the chemical warfare community over how (or whether) the data from the dog experiments applied to humans - British experiments with goats had led them to the opposing conclusions about its utility. This disagreement led to one of the more dramatic (and foolhardy) moments in the history of research on chemical warfare agents. A British researcher, Joseph Barcroft, emphatically disagreed with the French estimates of lethality. In order to prove his point, he sneaked into a testing chamber at Porton Down along with a dog but without a gas mask (although he did bring along a witness who stayed outside the chamber). Hydrogen cyanide was introduced into the chamber to give a concentration of about 500 mg m-3. Barcroft gave this description of what happened:
In order that the experiment might be as fair as possible and that my respiration should be relatively as active as that of the dog, I remained standing, and took a few steps from time to time while I was in the chamber. In about thirty seconds the dog began to get unsteady, and in fifty-five seconds it dropped on the floor and commenced the characteristic distressing respiration which heralds death from cyanide poisoning. One minute thirty-five seconds after the commencement the animal's body was carried out, respiration having ceased and the dog being apparently dead. I then left the chamber.This experiment, combined with the existing perception that hydrogen cyanide dispersed too rapidly to produce an effective concentration, meant that hydrogen cyanide was largely ignored as a military agent by most countries after the First World War. It is also frequently cited as an example of the hazards of extrapolating from animal models to humans.
Nevertheless, the Japanese investigated hydrogen cyanide. Tests were conducted on human subjects, including in at least one case a small child, in China at the facilities of the notorious unit 731 in conjunction with the Chemical Warfare Unit 516 using a telephone box-sized chamber. There is also evidence that Japanese forces may have used hydrogen cyanide or a related agent in chemical attacks in China on as many as 36 occasions between 1938 and 1941. It would, however, remain a very minor agent in the Japanese inventory, with about 250 tons being produced for the Imperial Japanese Army between 1930 and 1945.
Only the Soviet Union would invest significantly in weapons based on hydrogen cyanide. They had figured out that if you used a big enough charge in your bomb you got evaporative cooling that would allow production of an effective concentration at ground level. They had also developed spray tanks that allowed dissemination of enough agent to produce an effective concentration at ground level (with low altitude spraying). The Soviets also saw an advantage to the use of hydrogen cyanide in that most gas mask filters of the day worked relatively poorly against it. While the Soviets, like most countries, intended to use mustard gas as their main agent, they produced a significant quantity of hydrogen cyanide - figures are difficult to come by, but wartime (1940-1945) production totaled at least 11,104 tons.
During the Second World War, the Germans captured some Soviet spray tanks and tested them at their facility at Munsterlager, and were considerably disturbed by what they found - both unprotected animals and animals inside tanks (the panzer kind) died after about a minutes. The German gas mask was also poor protection against this particular agent, with the FE-41 filter failing in about an hour, and the FE-42 in about an hour and forty-five minutes (in contrast, the MT-4 mask the Soviets were issuing would last about 8 hours). This knowledge probably served as a disincentive for German use of chemical weapons in the East.
The most significant use of hydrogen cyanide during World War II was in the concentration camps. The principle agent used to murder those that the Nazi regime deemed undesirable was Zyklon B, which was hydrogen cyanide (40% by weight) absorbed on a calcium sulfate carrier.
After the Second World War, the importance of hydrogen cyanide as a chemical warfare agent diminished rapidly, primarily as a result of the rise of nerve agents. Even the Soviets, who had made themselves the masters of its use, relegated it to the third tier of their chemical arsenal, classifying it as a reserve agent.
But, although reduced in importance, allegations of its use still crop up from time to time. For instance, in February of 1985, the government of Thailand complained to the UN that rockets containing phosgene gas and hydrogen cyanide launched by Vietnamese forces fighting Cambodian rebels had landed on Thai territory. More famously, hydrogen cyanide is supposed to have been one of the agents in the chemical cocktail used against Halabja in the chemical assault carried out by Iraqi forces on that city on March 16-19, 1988. (This allegation remains controversial, as the cyanide residues on which it is based could also have arisen from impurities in the Tabun that was definitely used and the mix of agents employed makes identifying it from symptoms impossible. It has also been suggested that hydrogen cyanide may have come from an Iranian, rather than an Iraqi, chemical attack.)
Hydrogen Cyanide and Capital Punishment
After World War I, the use of chemicals for executions was considered, this being thought to be a more humane alternative than existing methods. In 1921, the Nevada state legislature authorized the use of lethal gas to execute capital convicts. The gas settled on was hydrogen cyanide because of its recognized lethality and simplicity of generation.
The original plan involved gassing the convict in his cell while he was sleeping, but this was quickly seen to be impractical, and a sealed gas chamber was constructed which was used for the first time on February 8, 1924. Subsequently, gas chambers were employed in eleven states and in some other countries for executions. However, the gas chamber as a means of execution was largely overshadowed by electrocution and, in recent years, by lethal injection methods when capital punishment is retained (only six states still use lethal gas, and all have an option of other methods).
Hydrogen Cyanide and Criminal Activity
Hydrogen cyanide has figured in many murder mysteries, although its actual use for premediated murder by individuals is rare. This is most likely because the most likely manner in which an individual would produce it would be from one of the cyanide salts (which are more commonly used for murder), and it is simpler to just use the salt, rather than generate the gas.
It does sometimes appear in criminal hands, however. In April of 2000 police who had entered a house in Vancouver, Canada found a marijuana nursery protected by a fused pipe bomb positioned next to a jar of "liquid cyanide."
In the United States there have been a number of successful prosecutions for murder when employee deaths have resulted from exposure to hydrogen cyanide when the employees were not properly warned or protected. The first of these was the result of the death of a 61-year-old Polish-born Stefan Golab, an employee of Film Recovery Systems Inc., a Chicago-based company that recovered silver from used photographic film. When investigation showed that information on the nature of the process and the hazards of the chemicals used had essentially been hidden from employees, Cook County brought charge, and three of the firm's executives were convicted of murder and sentenced to prison terms of up to 25 years.
There has been significant interest in the use of hydrogen cyanide as a weapon of assasination. In particular, Communist bloc intelligence services designed (and used) several weapons that disseminated it. This was dramatically revealed in 1961 when Bogdan Stashinsky, a KGB assassin, decided to defect and revealed the details of the murders of Lev Rebet and Stefan Bandera (anti-Soviet Ukrainians living in what was then West Germany). The weapon used was a simple tube containing a glass ampule of hydrogen cyanide which was crushed when the weapon was triggered, expelling the cyanide into the face of the intended victim. It had to be used at close range (less than half a meter), and the assassin was provided with an antidote pill to be taken immediately before using the weapon and a second antidote (presumably amyl nitrite) to inhale immediately after use.
The high local concentration produced ensured that the agent acted very rapidly to produce unconsciousness and death, while the volatility of hydrogen cyanide minimized obvious traces. The expectation was that, absent obvious signs of violence, the small traces would be ignored and the deaths of those killed using the weapon would be put down, at least officially, as due to natural causes such as heart attacks. This may well have been the case - Stashinsky was told in 1957, when he was first issued one of the weapons for the assassination of Rebet, that it had been used many times before with no problems, and when he was sent to assasinate Bandera in 1959, the KGB had seen no reason to alter the weapon or its mode of use (although they might have done so after Bandera's death - the circumstances were suspicious enough that a careful examination was carried out, which detected both the presence of cyanide residues in his system and glass fragments from the ampule on his face, leading to a murder investigation).
Terrorists and Hydrogen Cyanide
While cyanide salts have been used since antiquity to poison food and drink (and more recently, and infamously, Tylenol) hydrogen cyanide has only rarely figured in the plans of non-state actors, and there primarily as a threat (if that - the late 1960's "plan" by a faction of the right wing Minuteman group to introduce hydrogen cyanide into the UN's ventilation system would have been more credible if it had been clear that the planners knew where the air intakes were, for instance). But, while the past holds only a small role for it, recent events suggest disturbingly that hydrogen cyanide may figure more prominently in terrorist plans.
Ramzi Yousef, convicted in the 1993 World Trade Center bombing, indicated that he had intended to use sodium cyanide to create a cloud of cyanide gas to accompany the blast. How this would have been done is unclear. A small amount of cyanide was found in the supplies of the bombers, and the Judge during sentencing expressed the belief that some had been incorporated in the bomb. However, there was no evidence presented in open court that this had been done (if it was, the gas was certainly consumed in the explosion, and had no effect), and Yousef also indicated that his intention to use cyanide was thwarted by a lack of funds.
In January of 1995, Russian military authorities claimed that Chechen rebels had used hydrogen cyanide in attacks on Russian troops in the previous year. The use had involved pouring liquid hydrogen cyanide (presumably from an industrial source) onto highways where evaporation would produce a vapor hazard. An investigating committee dispatched by the Russian Duma found no evidence of this use and there were no casualties reported, and it has been suggested that this may be propaganda on the part of the military. However, the volatility of hydrogen cyanide would mean that few traces would be left, and such an attack, using materials intended for industry, would certainly have been within the capabilities of the rebels.
Attempted Use by Aum Shinrikyo
On May 5, 1995, members of Aum Shinrikyo attempted an attack on Shinjuku station in Tokyo by setting fire to a plastic bag of sodium cyanide positioned next to a bag of an acid placed in a men's room. The bags were discovered and extinguished. Then, on July 4, 1995, a similar combination of chemicals, this time with a timer, was discovered by a cleaning woman at the Kayabacho underground station. The police disarmed the device, preventing any injuries. Had either device functioned as planned, a significant quantity of hydrogen cyanide would have been produced.
It is believed that the al Qaeda terrorist group has produced and developed plans for the employment of chemical weapons, including hydrogen cyanide. This belief is based on several pieces of information:
On February 19, 2002, Italian police arrested 4 Morrocan men who were said to be planning a chemical attack on facilities in Rome. Among the materials seized were about nine pounds of potassium ferrocyanide. Initial reports, which identified the material seized as a cyanide compound, along with information on a previous plot thought to involve hydrogen cyandide (see under al Qaeda above) fueled speculation that the material would be used to generate hydrogen cyanide. However, potassium ferrocyanide is relatively unsuitable for this purpose, as very vigorous conditions are needed to produce hydrogen cyanide from it. It seems most likely at this writing that the men arrested planned to use it in a more prosaic manner - poisoning the water supply - although it is highly questionable how effective it would have been in this application.
The Ansar Al-Islam group, a fundamentalist Islamic group which controls territory in Northern Iraq, claimed to have stocks of cyanide gas which it said it would use against American forces in the event of an American-led attack on Iraq.
William J. Krar, of Tyler Texas, plead guilty on November 13, 2003 to one count of Possessing a Dangerous Chemical Weapon. The weapon in question was a large quantity of sodium cyanide which was discovered along with a variety of acids in a storage unit in Tyler, Texas during a court-authorized search. The quantities of acids and sodium cyanide discovered would have allowed the generation of enough hydrogen cyanide to produce lethal concentrations within a building of 30,000 square feet. The search resulted from an investigation into a package of false documents that had been traced back to Mr. Krar and some associates (the documents in question were extremely varied, which had lead to an investigation that included the FBI, the ATF, the Army Criminal Investigation Division, and the Defense Department Criminal Investigative Service). Mr. Krar was described in an affadavit for a search warrant as "actively involved in the militia movement." It was also indicated that he had ties to white supremacist and anti-government militia groups in New Hampshire.
In 2005, a six-man terrorist cell calling itself the al-Khattab brigade planned to attack American tourists in Jordan using cyanide. They changed their plans when they learned that puchases of cyanide were subject to controls, deciding to use machine guns instead. The Jordanian authiorites interrupted the plot before it was carried out, capturing the men.
|Toxic effect of hydrocyanic acid gas||987.7|
|Toxic effect of unspecified gases, fumes, or vapors||987.9|
|Accidental poisoning by other specified solid and liquid substances||E866.8|
|Accidental poisoning by unspecified solid and liquid substances||E866.9|
|Accidental poisoning by other specified gases and vapors||E869.8|
|Accidental poisoning by unspecified gases and vapors||E869.9|
|Suicide and self-inflicted poisoning using other and unspecified solid and liquid substances||E950.9|
|Suicide and self-inflicted poisoning using other specified gases and vapors||E952.8|
|Suicide and self-inflicted poisoning using unspecified gases and vapors||E952.8|
|Assault by poisoning using other solid and liquid substances||E962.1|
|Assault by poisoning using other gases and vapors||E962.2|
|Injury due to terrorism involving chemical weapons||E979.7||Injury due to war operations by gases, fumes, and chemicals||E997.2|
|Death due to terrorism involving chemical weapons||U01.7|
|Accidental poisoning by and exposure to other and unspecified chemicals and noxious substances||X49|
|Intentional self-poisoning (suicide) by and exposure to other gases and vapors||X67|
|Assault (homicide) by gases and vapors||X88|
|Assault (homicide) by other specified chemicals and noxious substances||X89|
|Assault (homicide) by unspecified chemical or noxious substance||X90|
|War operations involving chemical weapons and other forms of unconventional warfare||Y36.7|
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