SPECTRUM

Chemical Fact Sheet

Chemical Abstract Number (CAS #) 505602
CASRN 505-60-2
SynonymsMustard gas
Ethane, 1,1'-thiobis[2-chloro-
bis(2-Chloroethyl) sulfide
Sulfur mustard
Yperite
HD (chemical warfare agent)
Analytical Methods EPA Method 826
Molecular FormulaC4H8Cl2S

Link to the National Library of Medicine's Hazardous Substances
Database for more details on this compound.

Use VESICANT IN CHEMICAL WARFARE, MODEL CMPD IN BIOLOGICAL STUDIES ON ALKYLATING AGENTS ORG SYNTHESIS Medication: Formerly used topically in the treatment of psoriasis. MUSTARD GAS WAS USED AS A VESICANT IN CHEM WARFARE DURING WORLD WAR I & IN ETHIOPIA IN 1936 ALTHOUGH NO FURTHER MILITARY USE WAS REPORTED, PRODUCTION & STOCKPILING CONTINUED, ESPECIALLY DURING WORLD WAR II & STOCKS MAY STILL HAVE EXISTED IN USA AS RECENTLY AS 1974
Apparent Color COLORLESS OILY LIQUID ; YELLOW PRISMS ; OILY LIQUID FORMS PRISMS ON COOLING
Odor WEAK, SWEET, AGREEABLE ODOR
Boiling Point 217 DEG C
Melting Point 13-14 DEG C
Molecular Weight 159.07
Density 1.2741 @ 20 DEG C/4 DEG C LIQ
Odor Threshold Concentration 1.30X10-3 mg/l (gas) (detection in air, chemically pure) 2.30X10-3 ppm (detection in air, purity not specified) Odor 0.0150 mg/cu m (low) odor 0.0150 mg/cu m (high).
Sensitivity Data SEVERE IRRITANT TO SKIN, EYES & RESPIRATORY TRACT
Environmental Impact Bis(2-chloroethyl) sulfide (HD, mustard gas) may be released to the environment during its production, storage, transport, and disposal, as well as during its clinical and research use as an alkylating agent. When released on soil at low concns, bis(2-chloroethyl)sulfide should be lost by hydrolysis and volatilization. Some leaching should also occur. However, no experimental data are available on the fate of very low concns of bis(chloroethyl)sulfide in soil. When bis(2-chloroethyl)sulfide is introduced into water at very low concns so that it is dissolved, it will rapidly hydrolyze, forming mustard chlorohydrin and thiodiglycol. At 0, 25, and 40 deg C, the estimated half-lives of bis(2-chloroethyl)sulfide when dissolved in large amounts of water are 1.75 hr, 4 minutes, and 43 seconds, respectively. Volatilization will be slow by comparison. Hydrolysis in seawater will be a factor of 2.5 slower because of the common-ion effect exerted by the chloride ion. Despite its high rate of hydrolysis, undissolved bis(2-chloroethyl)sulfide may persist for longer periods of time because its rate of solution is slow. In the atmosphere, bis(2-chloroethyl)sulfide vapor will degrade primarily by reaction with photochemically-produced hydroxyl radicals; the resulting half-life is 1.4 days. Releases in chemical warfare may be by aerial spraying or from bursting munitions that would shower droplets of the chemical agents over the terrain. The persistence of HD sprayed on several soils at a variety of weather conditions ranged from 31 to 51 hr at 25 deg C and 50 to 92 days at 0 deg C. Persistence was lowest for heavy rain and highest in light rain. Persistence on snow has reported to range from 14-56 days. The bis(2-chloroethyl)sulfide does not appear to migrate into the snow, but rather stays on the surface. Disposal by land or sea burial might result in releases of large quantities of neat bis(2-chloroethyl)sulfide . Bulk quantities of bis(2-chloroethyl)sulfide buried on land may last for decades. When bulk quantities of bis(2-chloroethyl) sulfide are disposed of at sea, some bis(chloroethyl)sulfide will form a surface film that will disappear as a result of hydrolysis and volatilization within several days. Most of the bis(chloroethyl)sulfide will sink to the bottom of the water because bis(chloroethyl)sulfide is heavier than water. This bis(chloroethyl)sulfide will be degraded by hydrolysis; however, the hydrolysis will be limited by the rate of dissolution. The rate of dissolution will depend on the exposed surface, the amount of agitation, and the temperature. The temperature at the bottom of a body of water may be below 14.4 deg C and bis(chloroethyl)sulfide will then be a solid. Dissolution under these circumstances may take several months to years. Dissolved bis(chloroethyl)sulfide in the main body of seawater will be lost by hydrolysis with its half-life ranging from 15 min at 25 deg C to 175 min at 5 deg C.
Environmental Fate TERRESTRIAL FATE: FOR SOME TIME AFTER JULY 1917, MUCH OF FRENCH SOIL IN REGION OF BATTLE LINES WAS CONTAMINATED WITH MUSTARD GAS IN AREA OF FALLING SHELLS IN FRANCE HAVE BEEN ESTIMATED TO BE 3 & 5 PPM, RESPECTIVELY TERRESTRIAL FATE: When bis(2-chloroethyl) sulfide (HD) is released in soil, losses would primarily result from volatilization and hydrolysis. Some leaching will also be expected. For some time after 1917, much of the French soil in the region of the battle lines was contaminated with mustard gas, suggesting that HD is reasonably persistent in soil . Field reports dating back to World War I report that after used as a chemical warfare agent, an area is safe after 3 days to 3 weeks . The World Health Organization reports a persistence of 12-48 hr at 10 deg C with rain and a moderate wind, 2-7 days at 15 deg C with sun and a light breeze, and 2-8 wk at -10 deg C with sun, no wind, and a snow cover . Experimental measurements of concn of HD in the soil or in the air above the soil were not reported; HD levels were simply considered low enough for soldiers to reenter the area. Soldiers have been burned while digging in areas where HD has not been used for 3 yr and it has lasted for several decades in land dumps. This indicates that HD may be very persistent in soil, especially when bulk quantities are involved . The case of soldiers being burned by HD while digging in an area where it had not been used for 3 years, suggests that the HD had leached into the soil. TERRESTRIAL FATE: When disseminated over bare or vegetated terrain, water may be quite limited and may be largely derived from the atmosphere; hydrolysis would therefore depend on the humidity and the diffusion of water vapor into an agent droplet . When disseminated over snow and ice, water will be plentiful and taken up according to the agent's solubility; locally concentrated, unbuffered solutions may result . Even then, HD hydrolysis may be limited by its low solubility and the fact that it freezes at 14 deg C. The persistence in five soils ranged from 27 to 68 hr, with sand having the longest persistence and gravelly soil the least(2,SRC). Calculated values for pooled samples at 25 deg C for a variety of weather conditions are (weather condition - persistence in terms of agent density decline in hours): calm, dry - 41.5; windy, dry - 47.3; light rain - 51.2; heavy rain - 30.5 . At 0 deg C the respective persistence times were 63.8, 72.6, 92.3, 49.7 days . It is not clear why volatilization losses are lowest under conditions of light rain or why the half-life should be greater under windy conditions than calm ones. TERRESTRIAL FATE: The nature of the terrain has an important bearing on the behavior of the contaminant. Evaporation from grassland will be more rapid than from a permeable surface such as sand . In a field experiment designed to simulate a chemical attack, a small sample of HD was placed on top of the snow surface; another sample was immediately covered with 5 cm of snow in order to simulate a snowfall after an attack . Less than 0.1% of the HD was found after 14 days in both the uncovered and snow-covered samples. Experiments clearly showed that covering the sample with snow and increasing droplet size increased persistence; this has been ascribed to reduced volatilization and dissolution. None of the agents studied, including HD, tended to migrate into the snow. Another investigator reported a persistence of 56 days in snow at -10 deg C . In view of the fact that snow samples are quite variable, this value is not necessarily in conflict with the first (14 day) result. It has been suggested that HD may react in warm, dry soil to form 1,2-bis(2-chloroethylthio)ethane and higher adducts; however, no experimental evidence of such reactions have been reported. AQUATIC FATE: When bis(2-chloroethyl) sulfide (HD) is introduced into water at very low concns so that it is dissolved, it will rapidly hydrolyze, forming mustard chlorohydrin (CH) and thiodiglycol (TDG). At 0, 25, and 40 deg C, the estimated half-lives of HD when dissolved in large amounts of water are 1.75 hr 4 minutes, and 43 seconds, respectively. Hydrolysis in seawater will be a factor of 2.5 slower because of the common-ion effect exerted by the chloride ion. On the other hand, the half-life resulting from volatilization is expected to be much lower, 1.9 days from a model river and longer in a pond or lake. The situation is radically different at low temperatures and in heterogeneous mixtures. The rate of dissolution of HD is very slow. HD is a solid below 14.4 deg C which exacerbates this situation. At higher concn of HD, sulfonium salts (HD-TDG, HD-2TDG, CH-TDG) may form from the reaction of TDG with HD or CH; an equilibrium exits between TDG and CH-TDG. High HD concns may exist around HD droplets and when water dissolves inside an HD droplet. AQUATIC FATE: When HD is introduced into seawater, three zones with different behavior are observed . A small amount of HD will remain on the surface in a surface film where it will be destroyed by hydrolysis and to some extent volatilization; this surface film may last from one to several days. Bulk HD, or droplets formed by wind action on the surface film, will sink to the bottom of the water because HD is heavier than water. This HD will be degraded by hydrolysis; however, the hydrolysis rate will essentially be the rate of dissolution. The rate of dissolution will depend on the exposed surface, the amount of agitation, and the temperature. The temperature at the bottom of body of water may be below 14.4 deg C and HD will then be a solid. Dissolution under these circumstances may take several months at the very least; a one ton solid cylinder of HD would take about 5 yr to dissolve. In the water column of a body of seawater, dissolved HD will be lost by hydrolysis with its half-life ranging from 15 min at 25 deg C to 175 min at 5 deg C. ATMOSPHERIC FATE: When used as a chemical agent, bis(2-chloroethyl) sulfide (HD will be disseminated using aerial sprays or munitions and will be initially in the form of droplets. These droplets would be subject to gravitational settling; HD vapor from resulting deposits may reenter the atmosphere by evaporation. In the atmosphere, HD vapor will degrade by reaction with photochemically produced hydroxyl radicals; the resulting half life being estimated as 1.4 days.

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