History:
The first blister agent synthesised was mustard gas (sulphur mustard) in 1822, then first used by Germany during the first world war. It was then in turn used by the allies, although to a lesser extent.
It was discovered in 1935 that the sulphur atom in mustard gas could be replaced by nitrogen. This new agent, nitrogen mustard was stockpiled during the second world war, but (fortunately) never used.
Typical agents:
- Sulphur mustard (MD)
Formula: Cl-CH2-CH2-S-CH2-CH2-Cl
Synonyms: 2,2'-di(chloro-ethyl)-sulphide
Sub-agents: Distilled mustard (HD)
Description: Colourless or yellow, oily liquid with a weak rancid garlic or mustard like odour, hence "Mustard gas". Very penetrating, penetrates paint, cloth and wood easily. Very persistant, can remain on the ground for months, during World War I it was known to freeze to the ground during winter and still remain after the spring thaw. Effects felt 2 to 24 hours after exposure.
- Nitrogen mustard (HN)
Sub-agents:
Bis- (2-chloroethyl) ethylamine (HN-1): (Cl CH2 CH2)2 NC2 H5
2,2'-Dichloro-N-methyldiethylamine (HN-2): (Cl CH2 CH2)2 N C H3
Tris- (2-chloromethyl) amine Hydrochloride (NH-3): N(CH2-CH2-Cl)3
Description: Dark and oily liquids, similar odour to sulphur mustard but more dangerous than sulphur mustards. HN-2 is most dangerous of the three, but HN-3 is more likely to be used since it is more stable. Otherwise, effects same as sulphur mustard.
-
Phosgene Oxime (CX)
Formula: CH Cl2 NOH
Synonyms: Dichloroformoxime
Description: At room temperature, a white crystalline powder. Melts at 40°C, addition of certain compounds liquifies phosgene oxime at room temperature. Effects occur immediately after exposure. Otherwise, same as sulphur/nitrogen mustard.
-
Lewisite (L)
Formula: C2 H2 As Cl3
Synonyms: Dichloro (2-chloro-vinyl) arsine
Description: Dark oily liquid. A fast acting blister agent, with more pronounced blistering than most. At low concentrations, symptoms can occur in 30 minutes. High concentrations can kill in 10 minutes.
-
Phenyldichloroarsine (PD)
Forumla: C6 H5 As Cl2
Description: No odour or colour, usually a liquid. Slightly less effective than sulphur mustard, exactly same otherwise.
-
Ethyldichloroarsine (ED)
Formula: C2 H5 As Cl2
Description: Causes immediate irritating effect to anyone exposed to it. Less persistant than sulphur mustard, otherwise the same.
Manufacture:
Manufacture of sulphur mustard can be carried out by treating ethylene with sulphur chloride (Levinstein process)
or by treating 2,2'-dihydroxyethyl sulphide with Hydrochloric acid gas.
The other agents are similarly simple enough to produce.
Contamination:
Contamination from blister agents occours through the skin, eyes and via
respiration. Accordingly the symptoms of the contamination manifest themselves in those areas.
Mustard agents are easily able to penetrate a great number of materials, woods, leather,
rubber, plants, etc. Thus materials such as clothes offer no protection as long as they are in
contact with the skin.
To
prevent contamination of clothing, special protective equipment must be used, including
respirator, gloves, overboots etc.
Due to their
physical properties, mustards are very persistent in cold and temperate climates, as mentioned above they where known to
freeze in winter, and remain
toxic during the
thaw.
Unlike
nerve agent, there is no preventative drug that can be taken before
exposure to
reduce or prevent the effects of
any of the agents listed above.
Effects:
The effects of blister agents all tend to be similar, the main differences between the effects of different agents is the time till the effect occurs and the amount of damage to skin and eyes.
Typically, once the effects are felt the damage has all ready been done.
Symptoms of mild contamination include: aching eyes (tearing), inflammation of the skin, coughing, sneezing, and hoarseness.
A heavy dose is usually a worsening of the previous symptoms, including: respiration difficulty, vomiting, blistering and diarrhoea.
The primary effect of all these agents is blistering (lesions) upon areas of the skin which have been exposed.
The eyes are more susceptible to these agents than the respiratory tract or the skin.
Conjunctivitis (inflammation of mucous that coats eye and inside of eyelids, redness and discharge of the eyes), follows after 1 hour to concentrations barely perceptible by odour, that wouldn't affect respiratory tract significantly.
Heavy exposures irritate the eyes after 1 to 3 hours, and cause severe lesions (blisters).
New blisters can appear as late as two weeks after exposure.
The lesions tend to be painful on most areas of the skin, but areas with sensitive/thin skin are the most sensitive, and include the face, armpits, genitalia and neck.
The lesions tend to burst spontaneously giving way to a necrotic wound. Necrosis (dead cells) of the skin is
extended to the underlying tissues. The damaged tissues are susceptible to infection. Regeneration of the wounded area is slow, taking weeks to months to repair naturally. The healed skin is typically scarred and fragile.
Damage to the lungs is similar to choking agents, albeit weaker. If the dose is high enough, the victim dies via pulmonary oedema(fluid buildup in lungs) or suffocation due to dead tissue in lungs.
As with external lesion wounds, the lungs will be likely to be infected after approximately 48 hours, and difficulty in breathing will persist.
Eating contaminated food or water causes damage to the gastro-intestinal tract, causing nausea, vomiting and diarrhoea. The damage done may cause vomit and faeces to be bloodstained.
Decontamination
Treat eyes with isotonic sodium bicarbonate (1.26%) or saline solution (0.9%). Wash out thoroughly, avoid re-contaminating eyes by touching with contaminated hands.
Skin decontamination should be achieved with, physical absorption and checmial inactivation by chlorinating compounds or organic solvents.
Chlorination is effective against mustard and lewsite, less so gainst HN-3, and not at all against phosgene oxime.
Thus a cloth soaked in chlorinated water (3000ppm free chlorine) or petrol (unleaded gasoline) is suggested for skin decontamination.
Do not use water to remove mustard agents, as it decomposes into hydrochloric acid and may just spread the agent, rather than remove it.
Clean wounds with 3000ppm free chlorine water or saline solution, but not on abdominal or head injuries.
Contaminated clothing should be sealed away and destroyed, touching the contaminated clothing will re-contaminate unless protective gloves are worn.
Treatment:
Since there is no drug to combat the agent directly, treatment must focus on: decontamination, relieving symptoms, promoting healing and preventing infection.
Symptoms may take a while to develop, and hence the victim should be regularly re-assesed.
The victim must first be thoroughly decontaminated, contaminated clothing should be removed and destroyed. Then the eyes and skin should be decontaminated thoroughly, as blister agents are very persistant.
Vaseline should be applied to the eyelids to prevent them sticking together. Ointments and creams to reduce itching of lesions is not recommended, since these may aid infection.
Prevention of infection is an important element of treatment, the relevant antibiotics should be given to prevent infection. Victims who have inhaled agents are vunerable to bronchitis, pneumonia and other lung infections.
Once a lesion has burst, the roof should be removed, so that the wound can be more easily inspected and cleaned. There is no ideal treatment for the wounds, decontamination and initial severity of the lesions is more important to recovery than subsequent treatment.
Sources:
http://www.fas.org/irp/cia/product/go_appendixb_032796.html
http://www.fas.org/nuke/guide/usa/doctrine/dod/fm8-9/3ch3.htm
http://www.geocities.com/CapeCanaveral/Lab/4239/chemweapons/blister.html
And others...