mustard gas mustard gas mustard gas or sulfur mustard is any of several chemical compounds that contain the chemical structure sch2ch2cl. in the wider sense, compounds with the substituent sch2ch2x and nch2ch2x are known as sulfur mustards and nitrogen mustards (x = cl, br), respectively. such compounds are potent alkylating agents, which can interfere with several biological processes. also known as mustard agents, this family of compounds are infamous cytotoxic and blister agents. the name mustard gas is technically incorrect: the substances, when dispersed, are often not gases but a fine mist of liquid droplets. mustard gases form blisters on exposed skin and in the lungs, often resulting in prolonged illness ending in death. the typical mustard gas is the organosulfur compound called bis(2-chloroethyl) sulfide. history as chemical weapons sulfur mustard is a type of chemical warfare agent. as a chemical weapon, mustard gas was first used in world war i, and has been used in several armed conflicts since then, including the iran–iraq war, resulting in more than 100,000 casualties. today, sulfur-based and nitrogen-based mustard agents are regulated under schedule 1 of the 1993 chemical weapons convention, as substances with few uses other than in chemical warfare (though since then, mustard gas has been found to be useful in cancer chemotherapy). mustard agents could be deployed by means of artillery shells, aerial bombs, rockets, or by spraying from aircraft. mechanism of cellular toxicity mustard gas alkylating an amino group via conversion to a sulfonium ion (2-chloroethylthiiranium) sulfur mustards readily eliminate chloride ions by intramolecular nucleophilic substitution to form cyclic sulfonium ions. these very reactive intermediates tend to permanently alkylate nucleotides in dna strands, which can prevent cellular division, leading to programmed cell death. alternatively, if cell death is not immediate, the damaged dna can lead to the development of cancer. oxidative stress would be another pathology involved in mustard gas toxicity. in the wider sense, compounds with the structural element bc2h4x, where x is any leaving group and b is a lewis base, are known as mustards. such compounds can form cyclic "onium" ions (sulfonium, ammonium, etc.) that are good alkylating agents. other such compounds are bis(2-haloethyl)ethers (oxygen mustards), the (2-haloethyl)amines (nitrogen mustards), and sesquimustard, which has two α-chloroethyl thioether groups (clc2h4s−) connected by an ethylene bridge (−c2h4−). these compounds have a similar ability to alkylate dna, but their physical properties vary. physiological effects soldier with moderate mustard agent burns sustained during world war i showing characteristic bullae on the neck, armpit, and hands mustard gases react with dna, which interferes with cellular division and can lead to mutations. mustard gases are extremely toxic and have powerful blistering effects on victims. their alkylating capabilities make them strongly carcinogenic and mutagenic. furthermore, they are highly lipophilic, which accelerates their absorption into the body. because people exposed to mustard agents rarely suffer immediate symptoms, and contaminated areas may appear completely normal, victims can unknowingly receive high doses. within 24 hours of exposure, victims experience intense itching and skin irritation. if this irritation goes untreated, blisters filled with yellow fluid (pus) can start to form wherever the agent contacted the skin. these are chemical burns and are very debilitating. mustard gases easily penetrate clothing fabrics such as wool or cotton, so it is not only exposed skin that gets burned. if the victim's eyes were exposed, then they become sore, starting with conjunctivitis (also known as pink eye), after which the eyelids swell, resulting in temporary blindness. extreme ocular exposure to mustard gas vapors may result in corneal ulceration, anterior chamber scarring, and neovascularization. in these severe and infrequent cases, corneal transplantation has been used as a treatment option. miosis, when the pupil constricts more than usual, may also occur, which is probably the result of the cholinomimetic activity of mustard. at very high concentrations, if inhaled, mustard agents cause bleeding and blistering within the respiratory system, damaging mucous membranes and causing pulmonary edema. depending on the level of contamination, mustard agent burns can vary between first and second degree burns, though they can also be every bit as severe, disfiguring, and dangerous as third degree burns. burns that are severe (i.e. covering more than 50% of the victim's skin) are often fatal, with death occurring after only days or weeks. mild or moderate exposure to mustard gases is unlikely to kill, though victims still require lengthy periods of medical treatment and convalescence before recovery is complete. mustard gases' carcinogenic and mutagenic effects mean that victims, even if they fully recover, have an increased risk of developing cancer later in life. in a study of patients 25 years after wartime exposure to chemical weaponry, c-dna microarray profiling indicated that 122 genes were significantly mutated in the lungs and airways of mustard gas victims. those genes all correspond to functions commonly affected by mustard gas exposure, including apoptosis, inflammation, and stress responses. the long-term ocular complications include burning, tearing, itching, photophobia, presbyopia, pain, and foreign-body sensations. typical appearance of bullae on an arm caused by vesicant burns mustard gases' blistering effects can be neutralized by oxidation or chlorination, using household bleach (sodium hypochlorite), or by nucleophilic attack using decontamination solutions such as "ds2" (2% naoh, 70% diethylenetriamine, 28% 2-methoxyethanol). after initial decontamination of the victim's wounds is complete, medical treatment is similar to that required by any conventional burn. the degree of pain and discomfort suffered by the victim is also comparable. mustard agent burns do not heal quickly, and (as with other types of burns) present a risk of sepsis caused by pathogens such as staphylococcus aureus and pseudomonas aeruginosa. the mechanisms behind mustard gas's effect on endothelial cells are still being studied, but recent studies have shown that high levels of exposure can induce high rates of both necrosis and apoptosis. in vitro tests have shown that at low concentrations of mustard gas, where apoptosis is the predominant result of exposure, pretreatment with 50 mm n-acetyl-l-cysteine (nac) was able to decrease the rate of apoptosis. nac protects actin filaments from reorganization by mustard gas, demonstrating that actin filaments play a large role in the severe burns observed in victims. a british nurse treating soldiers with mustard agent burns during world war i commented: they cannot be bandaged or touched. we cover them with a tent of propped-up sheets. gas burns must be agonizing because usually the other cases do not complain, even with the worst wounds, but gas cases are invariably beyond endurance and they cannot help crying out. formulations lewisite (top row) and mustard gas (bottom row) test with concentrations from 0.01% to 0.06% in its history, various types and mixtures of mustard gas have been employed. these include: h – also known as hs ("hun stuff") or levinstein mustard. this is named after the inventor of the "quick but dirty" levinstein process for manufacture, reacting dry ethylene with disulfur dichloride under controlled conditions. undistilled mustard gas contains 20–30% impurities, which means it does not store as well as hd. also, as it decomposes, it increases in vapor pressure, making the munition it is contained in likely to split, especially along a seam, releasing the agent to the atmosphere. hd – codenamed pyro by the british, and distilled mustard by the us. distilled mustard of 95% or higher purity. the term "mustard gas" usually refers to this variety of mustard. ht – codenamed runcol by the british, and mustard t- mixture by the us. a mixture of 60% mustard and 40% o-mustard, a related vesicant with lower freezing point, lower volatility and similar vesicant characteristics. hl – a blend of distilled mustard (hd) and lewisite (l), originally intended for use in winter conditions due to its lower freezing point compared to the pure substances. the lewisite component of hl was used as a form of antifreeze. hq – a blend of distilled mustard (hd) and sesquimustard (q) (gates and moore 1946). commonly-stockpiled mustard agents (class) chemical code trivial name cas number pubchem structure bis(2-chloroethyl) sulfide h, hd mustard 505-60-2 cid 10461 from pubchem 1,2-bis(2-chloroethylsulfanyl) ethane q sesquimustard 3563-36-8 cid 19092 from pubchem 2-chloroethyl ethyl sulfide half mustard 693-07-2 cid 12733 from pubchem bis(2-(2-chloroethylsulfanyl)ethyl) ether t o-mustard 63918-89-8 cid 45452 from pubchem 2-chloroethyl chloromethyl sulfide 2625-76-5 bis(2-chloroethylsulfanyl) methane hk 63869-13-6 1,3-bis(2-chloroethylsulfanyl) propane 63905-10-2 1,4-bis(2-chloroethylsulfanyl) butane 142868-93-7 1,5-bis(2-chloroethylsulfanyl) pentane 142868-94-8 bis((2-chloroethylsulfanyl)methyl) ether 63918-90-1 history development mustard gases were possibly developed as early as 1822 by césar-mansuète despretz (1798–1863). despretz described the reaction of sulfur dichloride and ethylene but never made mention of any irritating properties of the reaction product. in 1854, another french chemist, alfred riche (1829–1908), repeated this procedure, also without describing any adverse physiological properties. in 1860, the british scientist frederick guthrie synthesized and characterized the mustard agent compound and noted its irritating properties, especially in tasting. also in 1860, chemist albert niemann, known as a pioneer in cocaine chemistry, repeated the reaction, and recorded blister-forming properties. in 1886, viktor meyer published a paper describing a synthesis that produced good yields. he combined 2-chloroethanol with aqueous potassium sulfide, and then treated the resulting thiodiglycol with phosphorus trichloride. the purity of this compound was much higher and consequently the adverse health effects upon exposure were much more severe. these symptoms presented themselves in his assistant, and in order to rule out the possibility that his assistant was suffering from a mental illness (psychosomatic symptoms), meyer had this compound tested on laboratory rabbits, most of which died. in 1913, the english chemist hans thacher clarke (known for the eschweiler-clarke reaction) replaced the phosphorus trichloride with hydrochloric acid in meyer's formulation while working with emil fischer in berlin. clarke was hospitalized for two months for burns after one of his flasks broke. according to meyer, fischer's report on this accident to the german chemical society sent the german empire on the road to chemical weapons. mustard gas can have the effect of turning a patient's skin different colors, including shades of red, orange, pink, and in unusual cases, blue. the german empire during world war i relied on the meyer-clarke method because 2-chloroethanol was readily available from the german dye industry of that time. use pallets of 155 mm artillery shells containing "hd" (distilled mustard gas agent) at the pueblo chemical depot. the distinctive color-coding scheme on each shell is visible mustard gas was first used in world war i by the german army against british and canadian soldiers near ypres, belgium, "on the night of july 12, 1917." later also against the french second army. yperite is "a name used by the french, because the compound was first used at ypres." the allies did not use mustard gas until november 1917 at cambrai, france, after the armies had captured a stockpile of german mustard shells. it took the british more than a year to develop their own mustard agent weapon, with production of the chemicals centred on avonmouth docks (the only option available to the british was the despretz–niemann–guthrie process). this was used first in september 1918 during the breaking of the hindenburg line. mustard gas was originally assigned the name lost, after the scientists wilhelm lommel and wilhelm steinkopf, who developed a method of large-scale production for the imperial german army in 1916. mustard gas was dispersed as an aerosol in a mixture with other chemicals, giving it a yellow-brown color. mustard agent has also been dispersed in such munitions as aerial bombs, land mines, mortar rounds, artillery shells, and rockets. exposure to mustard agent was lethal in about 1% of cases. its effectiveness was as an incapacitating agent. the early countermeasures against mustard agent were relatively ineffective, since a soldier wearing a gas mask was not protected against absorbing it through his skin and being blistered. a common countermeasure was using a urine-soaked mask or facecloth to prevent or reduce injury, a readily available remedy attested by soldiers in documentaries (e.g. they shall not grow old in 2018) and others (such as forward aid nurses) interviewed between 1947 and 1981 by the british broadcasting corporation for various world war one history programs; however, the effectiveness of this measure is unclear. mustard gas can remain in the ground for weeks, and it continues to cause ill effects. if mustard agent contaminates one's clothing and equipment while cold, then other people with whom they share an enclosed space could become