Vesicants

Blister agents or vesicants are an exception to the limited utility of classic agents. Although these materials have a relatively low lethality, they are effective casualty agents that inflict painful burns and blisters requiring medical attention even at low doses. The classic mustard gas is the most popular among those nations nations newly developing chemical warfare capability since it is relatively easy to make. Mustard is generally referred to as the "king" of agents because of its ease of production, low cost, predictable properties, persistence, and ability to cause resource-devouring casualties rather than fatalities. Delivered in liquid or vapour form, such weapons burn the skin, eyes, and respiratory tracts. The physical results, depending on level of exposure, might be immediate or might appear after several hours. Although lethal in high concentrations, blister agents seldom kill. At incapacitating levels this may be as long as 12 hours. Contrary to the normal expectation, horrible fatalities occurred in the Iran-Iraq War because Iranian soldiers, feeling no initial effects, continued to wear mustard soaked clothing and inhale its fumes. Untreated mustard casualties are likely to suffer acute respiratory reactions, and to contract serious infections from burns that have been treated too late.

1,2-Bis(2-chloroethylthio)ethane [Sesquimustard, Sesquisulfur Mustard, Sesquimustard Q, Sulfur mustard] - C₆H₁₂Cl₂S₂

Solid at room temperature.  A blister agent (vessicant) that causes severe, delayed burns to the eyes, skin, and respiratory tract. Sulfur mustard damages cells within minutes of contact; however, the onset of pain and other health effects is delayed until hours after exposure. Large exposures to sulfur mustard may be fatal. Sulfur mustard is also an alkylating agent that damages the cells within the bone marrow that are necessary for making blood cells; this affects the body's immune system. Finally, sulfur mustard also affects a part of the nervous system responsible for everyday bodily function, causing cholinergic toxicity, marked by excessive saliva, tears and urine; gastrointestinal  cramping and diarrhea; vomiting; and constricted or pinpoint pupils.

1,3-Bis(2-chloroethylthio)propane [Sulfur mustard] - C₇H₁₄Cl₂S₂

A blister agent  that causes severe, delayed burns to the eyes, skin, and respiratory tract. Sulfur mustard damages cells within minutes of contact; however, the onset of pain and other health effects is delayed until hours after exposure. Large exposures to sulfur mustard may be fatal. Sulfur mustard is also an alkylating agent that damages the cells within the bone marrow that are necessary for making blood cells; this affects the body's immune system. Finally, sulfur mustard also affects a part of the nervous system responsible for everyday bodily function, causing cholinergic toxicity, marked by excessive saliva, tears and urine; gastrointestinal (GI) cramping and diarrhea; vomiting (emesis); and constricted or pinpoint pupils.

1,4-Bis(2-chloroethylthio)-n-butane [Sulfur mustard] - C₈H₁₆Cl₂S₂

A blister agent (vesicant) that causes severe, delayed burns to the eyes, skin, and respiratory tract. Sulfur mustard damages cells within minutes of contact; however, the onset of pain and other health effects is delayed until hours after exposure. Large exposures to sulfur mustard may be fatal. Sulfur mustard is also an alkylating agent that damages the cells within the bone marrow that are necessary for making blood cells; this affects the body's immune system. Finally, sulfur mustard also affects a part of the nervous system responsible for everyday bodily function, causing cholinergic toxicity, marked by excessive saliva, tears and urine; gastrointestinal (GI) cramping and diarrhea; vomiting (emesis); and constricted or pinpoint pupils.

1,5-Bis(2-chloroethylthio)-n-pentane [Sulfur mustard] -  C₉H₁₈Cl₂S₂

A blister agent (vesicant) that causes severe, delayed burns to the eyes, skin, and respiratory tract. Sulfur mustard damages cells within minutes of contact; however, the onset of pain and other health effects is delayed until hours after exposure. Large exposures to sulfur mustard may be fatal. Sulfur mustard is also an alkylating agent that damages the cells within the bone marrow that are necessary for making blood cells; this affects the body's immune system. Finally, sulfur mustard also affects a part of the nervous system responsible for everyday bodily function, causing cholinergic toxicity, marked by excessive saliva, tears and urine; gastrointestinal cramping and diarrhea; vomiting; and constricted or pinpoint pupils.

2-Chlorovinyldichloroarsine [Lewisite]  - C₂H₂AsCl₃

Although, in the pure form, colourless and odourless, impure samples are a yellow, brown, violet-black, green, or amber oily liquid with a distinctive odor that has been described as similar to geraniums. It can easily penetrate ordinary clothing and latex rubber gloves. Upon skin contact it causes immediate stinging, burning pain and itching that can last for 24 hours. Within minutes, a rash develops and the agent is absorbed through the skin. Large, fluid-filled blisters (similar to those caused by mustard gas exposure) develop after approximately 12 hours and cause pain for 2 to 3 days. These are severe chemical burns and begin with small blisters in the red areas of the skin within 2 to 3 hours and grow worse, encompassing the entire red area, for the ensuing 12 to 18 hours after initial exposure. Liquid lewisite has faster effects than lewisite vapor. Sufficient absorption can cause lethal liver necrosis.

Bis(2-chloroethylthioethyl)ether [Sulfur mustard, O-Mustard, Agent T] - C₈H₁₆Cl₂OS₂

A colourless, nonflammable liquid with a strong unpleasant, nauseating odour, f. It dissolves easily in water, and some of it will slowly evaporate to the air. It does not occur naturally.

Bis(2-chloroethylthiomethyl)ether [Sulfur mustard, Oxygen mustard] - C₆H₁₂Cl₂OS₂

A colorless liquid with the odour of a chlorinated solvent

Bis(2-chloroethyl)ethylamine [HN1, Nitrogen mustard, Ethyl-S] - C₆H₁₃Cl₂N

Colorless to yellow, oily liquid that evaporates very slowly. HN-1 has a faint, fishy or musty odor.  A powerful vesicant. Effects of nitrogen mustard exposure can be long-term or permanent; it is also a known carcinogen, reprotoxin, and developmental toxin after chronic and acute exposure, causing skin cancer and airway cancers in particular. Blindness from an acute exposure is usually temporary, resolving in days to months depending on severity. Chronic respiratory and eye infections are also common after acute nitrogen mustard exposure. Other consequences of acute exposure include ageusia (lost of sense of taste), anosmia (loss of sense of smell), pulmonary fibrosis, scarring, bronchitis, chronic respiratory disease, mental illness, and central nervous system damage. Consequences of chronic exposure beyond cancer include permanent kidney damage and immuno-suppression.

Bis(2-chloroethyl)methylamine  [HN2, Nitrogen mustard, Mustargen]  -   C₅H₁₁Cl₂N

A soapy odour at low concentrations and a fruity odor at higher concentrations. Symptoms of toxic exposure to Bis(2-chloroethyl)methylamine vary based on the route of exposure. Eye exposure causes lachrymation, burning, irritation, itching, a feeling of grittiness or dryness, blepharospasm, and photophobia. More severe cases cause oedema in the eyelids, severe pain, corneal ulceration, and blindness. Early symptoms of inhalation include rhinorrhea, epistaxis, toneless voice, sneezing, barking cough, and dyspnea (in smokers and asthmatics). Later symptoms include pain in the nose/sinuses and inflammation of the airway. In severe cases, there may be epithelial necrosis throughout the respiratory tract, causing pseudo-membrane formation, which can obstruct the airway. Pneumonia may develop and prove fatal. Skin exposure mainly causes erythema  and blistering at first, but absorption through the skin causes systemic toxicity. In cases where more than 25% of the skin is affected, fatal exposure is likely to have occurred. Long-term effects of acute or chronic exposure are caused by damage to the immune system. White blood cell counts drop, increasing the risk of infection, and red blood cell and platelet counts may also drop due to bone marrow damage. Chronic eye infections may result from exposure, but blindness is temporary. Long-term effects on the respiratory system include loss of the sense of smell, loss of the sense of taste, inflammation, chronic infections, fibrosis, and cancer. Skin that has been damaged by can change pigmentation or become scarred, and may eventually develop cancer.

Dibromoethyl sulfide [Mustard gas, Brom LOS, Di(2-Bromoethyl) sulfide, Bis(2-bromoethyl)sulfide] - S(CH₂CH₂)₂Br₂

Oily yellow-brown liquid with garlic taste and mustard odor. After inhalation, it has delayed effects 2-24 hours after exposure. It penetrates the skin in 1-2 minutes without initial irritation. It is corrosive to skin and lung tissue resulting in skin blisters and haemoptysis.  The eyes, skin, and respiratory tract are most commonly affected. Eye exposure may result in temporary loss of vision.

Ethyldichloroarsine [Dick, EDn Dichloroethylarsine, Dichloro(ethyl)arsine, Arsenic dichloroethane] - C₂H5AsCl₂

Colorless liquid with a fruity, irritating odor. A powerful irritant that can induce pulmonary edema. Reacts with water on exposed membranes to release hydrochloric acid. The liquid produces blisters after an exposure of less than one minute.

Methyldichloroarsine [Methyldick, MD] - CH₃AsCl₂

A colourless volatile liquid. Its symptoms resemble those from poison ivy, other symptoms include irritation to the eyes and to the nose, although blistering may be delayed for hours. Other symptoms include: dermal burns with vesicle formation; blepharospasm and photophobia. Convulsions, abdominal pain, coughing, and shortness of breath with damage to the respiratory system can be delayed for about three to five days; haemolysis can also occur

Methyl (2-chloroethyl)nitrosocarbamate [KB-16, TL-186] - C₄H₇ClN₂O₃

Inhalation, ingestion or skin contact with material may cause severe injury or death. Effects of contact or inhalation may be delayed.

Phosgene oxime [CX] - Cl₂CNOH

Colourless in its solid form and yellowish-brown when it is a liquid, it has a disagreeable, irritating odor. Signs and symptoms occur immediately following a phosgene oxime exposure. Skin exposure causes pain occurring within a few seconds, and blanching (whitening) of the skin surrounded by red rings occurring on the exposed areas within 30 seconds. Within about 15 minutes, the skin develops hives. After 24 hours, the whitened areas of skin become brown and die, and then a scab is formed. Itching and pain may continue throughout the healing process. Eye exposure produces severe pain and irritation, tearing, and possibly temporary blindness. Inhalation causes immediate irritation to the upper respiratory tract, with runny nose, hoarseness, and sinus pain. Absorbing phosgene oxime through the skin or inhaling it may result in pulmonary edema with symptoms of shortness of breath and cough.

Tris(2-chloroethyl)amine [HN3, Nitrogen mustard, Tris(2-chloroethyl)amine hydrochloride, trichlormethine, HN3 hydrochloride] - N(CH₂CH₂Cl)₃

HN-3 may smell like bitter almonds. HN-3 can be absorbed into the body by inhalation, ingestion, eye contact, and skin contact (though inhalation is the most common). The chemical is extremely toxic and may damage the eyes, skin, and respiratory tract and suppress the immune system. It penetrates and binds quickly to cells of the body, but its health effects develop slowly. The full extent of cellular injury may not be known for days.

Tris(2-chlorovinyl)arsine [Lewisite 3] - C₆H₆AsCl3

Oily, clear to yellowish liquid. Causes a burning pain and irritation throughout the respiratory tract, epistaxis, laryngitis, sneezing, coughing, vomiting, dyspnea. From one acute exposure, someone who has inhaled lewisite 3 can develop chronic respiratory disease. In severe cases of exposure, can cause fatal pulmonary oedema, pneumonitis, or respiratory failure. Ingestion results in severe pain, nausea, vomiting, and tissue damage. Those exposed to lewisite 3 can develop refractory hypotension, as well as some features of arsenic toxicity. Lewisite 3 causes physical damage to capillaries, which then become leaky, meaning that there is not enough blood volume to maintain blood pressure, a condition called hypovolemia. When the blood pressure is low, the kidneys may not receive enough oxygen and can be damaged. The results of eye exposure can range from stinging, burning pain and strong irritation to blistering and scarring of the cornea, along with blepharospasm, lachrymation, and oedema of the eyelids and periorbital area. Eye exposure can cause permanent visual impairment or blindness. The eyes can swell shut, which can keep the eyes safe from further exposure. The most severe consequences of eye exposure to lewisite are globe perforation and blindness. Generalised symptoms also include restlessness, weakness, hypothermia and low blood pressure. Chronic exposure can cause arsenic poisoning and development of a lewisite allergy. It can also cause various long-term illnesses or permanent damage to organs, depending on where the exposure has occurred, including conjunctivitis, photophobia, visual impairment, diplopia,  lachrymation, dry mucous membranes, garlic breath, burning pain in the nose and mouth, toxic encephalopathy, peripheral neuropathy, seizures, nausea, vomiting, chronic obstructive pulmonary disease, bronchitis, dermatitis, skin ulcers, basal cell carcinoma, and squamous cell carcinoma.

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