A Look at Sarin

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Chemical exposure, especially to one such as sarin, is not something to which paramedics give a great deal of thought, after all many paramedic services have specialty teams trained in CBRN and CBRNE to handle these types of calls.  In today’s climate it would be naive to assume that there is no chance that you will come in contact with this type of exposure.  While we all hope that something this horrific will never happen it is important to expand our knowledge base to protect ourselves and our patients.

While it is extremely important to have speacialty teams in place and it is equally important that every medic on the road has a basic understanding of these chemicals, their effects, their treatments.

What sarin is

Sarin is a human-made chemical warfare agent classified as a nerve agent. Nerve agents are the most toxic and rapidly acting of the known chemical warfare agents. They are similar to certain kinds of insecticides called organophosphates in terms of how they work and what kind of harmful effects they cause. Nerve agents; however, are much more potent than organophosphate pesticides.  Sarin originally was developed in 1938 in Germany as a pesticide.

Sarin is a clear, colorless, and tasteless liquid that has no odor in its pure form and can evaporate into a vapour and spread into the environment.

Where sarin is found and how it is used

Sarin is not found naturally in the environment, it is a man-made toxin.  Sarin was used in two terrorist attacks in Japan in 1994 and 1995.

How people can be exposed to sarin

People can be exposed to sarin through direct topical contact the skin or eyes or through inhalation of sarin that has been vaporized.  These exposures can happen quickly after the initial release of sarin.

Sarin mixes easily with water and people can be exposed by touching or drinking water that contains sarin.  In addition people can be exposed by eating contaminated food.

A person’s clothing can release sarin after it has come in contact with sarin vapor, which can lead to exposure of other people.

Because sarin vapor is heavier than air, it will sink to low-lying areas and create a greater exposure hazard there.

How sarin works

The degree of poisoning caused by sarin depends on the amount of sarin to which a person was exposed in addition to the nature of the exposure. Symptoms likely will appear within a few seconds after exposure to the vapour form of sarin and within a few minutes to hours after exposure to the liquid form.

Nerve agents such as sarin cause their toxic effects by inhibiting acetylcholinesterase, an enzyme that catalyzes the breakdown of the acetylcholine neurotransmitter into acetate and choline.

Acetylcholine is a neurotransmitter that is released from pre-synaptic neurons to bind to acetylcholine receptors on post-synaptic neurons to trigger a downstream signal. When exposed to sarin, a cell’s normal metabolism of acetylcholine via acetylcholinesterase is disrupted, leading to excessive activation of the post-synaptic acetylcholine receptors.

Sarin is the most volatile of the nerve agents. This means it can easily and quickly evaporate from a liquid into a vapor and spread into the environment. People can be exposed to the vapor even if they do not come in contact with the liquid form of sarin.

Because it evaporates so quickly, sarin presents an immediate but short-lived threat.

Immediate signs and symptoms of sarin exposure

Sarin is odourless and people not know that they have been exposed to sarin.

People exposed to a low or moderate dose of sarin by breathing contaminated air, eating contaminated food, drinking contaminated water, or touching contaminated surfaces may experience some or all of the following symptoms within seconds to hours of exposure:

  • Runny nose
  • Watery eyes
  • Small, pinpoint pupils
  • Eye pain
  • Blurred vision
  • Drooling and excessive sweating
  • Cough
  • Chest tightness
  • Rapid breathing
  • Diarrhea
  • Nausea, vomiting, and/or abdominal pain
  • Increased urination
  • Confusion
  • Drowsiness
  • Weakness
  • Headache
  • Slow or fast heart rate
  • Low or high blood pressure

Even a small drop of sarin on the skin can cause sweating and muscle twitching where sarin touched the skin.

Exposure to large doses of sarin by any route may result in the following harmful health effects:

  • Loss of consciousness
  • Convulsions
  • Paralysis
  • Respiratory failure possibly leading to death
  • Showing these signs and symptoms does not necessarily mean that a person has been exposed to sarin.

Treatment of sarin exposure

There are two rescue medications that can be used to treat sarin exposure. The first, Pralidoxime, functions by breaking the bond between the sarin molecule and the acetylcholinesterase enzyme, thereby ending the inhibition. The second, Atropine, is an acetylcholine receptor antagonist, which prevents the excess acetylcholine from continually activating the acetylcholine receptor. If these medications are not provided soon after being exposed, those affected by the toxin may die within hours.
It should be noted that not all acetylcholinesterase inhibitors are exclusively harmful. Myasthenia Gravis is a muscular disease that is caused by the production of auto-antibodies that inhibit the acetylcholine receptor. In individuals affected by Myasthenia Gravis, drugs like Pyridostigmine, a competitive inhibitor of acetylcholinesterase, may relieve the symptoms of the disease. By increasing the synaptic concentration of acetylcholine, pyridostigmine could counteract the effects of the acetylcholine receptor-inhibiting antibody.

How people can protect themselves, and what they should do if they are exposed to sarin

Recovery from sarin exposure is possible with treatment, but to be effective, the antidotes available must be used quickly.

  • Remove the patient from the area where the sarin was released as quickly as possible.
  • If the sarin release was outdoors, go to the highest ground possible (sarin is heavier than air and will sink to low-lying areas).
  • Clothing should be removed rapidly and the patient’s entire body will need to be washed with soap and water. Remember that sarin is easily dissolved in water and that water is now potentially contaminated.
  • Removing and disposing of clothing:  
    • Quickly take off clothing that has liquid sarin on it. Any clothing that has to be pulled over the head should be cut off the body instead of pulled over the head. If possible, seal the clothing in a plastic bag. Then seal the first plastic bag in a second plastic bag. Removing and sealing the clothing in this way will help protect others from exposure.
  • Washing the body:
    • As quickly as possible, wash any liquid sarin from the skin with large amounts of soap and water. Washing with soap and water will help protect people from any chemicals on their bodies.
    • Flush and rinse eyes with plain water for 10 to 15 minutes if they are burning or if vision is blurred.
  • If sarin has been swallowed, do not induce vomiting or give fluids to drink.

What the long-term health effects are

Mildly exposed people usually recover completely. Severely exposed people are less likely to survive.

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