Chemical Agents: Vesicants, Choking Agents, Metabolic Agents, and Riot-control Agents Practice Questions

25 multiple-choice questions on Chemical agents: vesicants, choking agents, metabolic agents, and riot-control agents for paramedic and EMT students, from Chapter 51 (Terrorism Response). Read each question, pick your answer, then tap Show answer to check it and read the explanation.

25 practice questions

1. Sulfur mustard is especially insidious as a weapon because:

   1. A. Signs appear hours after exposure
   2. B. It causes instant pain on contact
   3. C. It spreads from person to person by cough
   4. D. It cannot pass through ordinary clothing
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   Answer: A. Signs appear hours after exposure

   Mustard causes no pain at the time of contact, so victims may not know they were exposed until redness, blisters, and eye pain appear 2 to 24 hours later. Instant pain on contact is the hallmark of lewisite, not mustard.

2. Several hours after a yellow-brown oily mist with a garlic odor drifted through an open-air market, many victims develop red skin, blisters, and burning eyes. The most likely agent is:

   1. A. Sarin vapor
   2. B. Sulfur mustard
   3. C. Chlorine gas
   4. D. Hydrogen cyanide
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   Answer: B. Sulfur mustard

   A garlic or horseradish odor, an oily liquid, and skin and eye injury that appears hours later fit sulfur mustard. Chlorine irritates the eyes and airway within minutes and does not raise skin blisters hours later.

3. The fluid inside blisters caused by sulfur mustard:

   1. A. Contains no active agent
   2. B. Is toxic to responders
   3. C. Spreads agent to nearby skin
   4. D. Must be drained in the field
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   Answer: A. Contains no active agent

   By the time blisters form, the agent has already reacted with tissue, so blister fluid is not a hazard to providers. Draining blisters in the field only raises infection risk.

4. Although mustard signs are delayed, decontamination should be done right away because the agent:

   1. A. Grows more toxic as hours pass
   2. B. Cannot be absorbed for about an hour
   3. C. Binds to tissue within minutes
   4. D. Stops harming skin once it is dry
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   Answer: C. Binds to tissue within minutes

   Mustard penetrates and binds to skin within minutes even though damage shows up hours later, so decon must be done at once to limit injury. Its toxicity does not increase with time; delayed decon simply comes too late.

5. The organ most sensitive to sulfur mustard is the:

   1. A. Liver
   2. B. Kidneys
   3. C. Heart muscle
   4. D. Eyes
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   Answer: D. Eyes

   The moist tissues of the eyes are injured at lower doses than skin, causing pain, light sensitivity, and swelling of the lids. The liver, kidneys, and heart are not the main targets; the skin and airway are next most affected.

6. A blister agent that causes immediate burning pain on contact and contains arsenic is:

   1. A. Lewisite
   2. B. Sulfur mustard
   3. C. Phosgene
   4. D. Tabun
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   Answer: A. Lewisite

   Lewisite causes pain within seconds, unlike mustard, which is painless at first. Phosgene is a choking agent that injures the lungs rather than raising skin blisters.

7. The specific antidote for the arsenic-based blister agent lewisite is:

   1. A. Atropine sulfate
   2. B. Dimercaprol (BAL)
   3. C. Hydroxocobalamin
   4. D. Pralidoxime chloride
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   Answer: B. Dimercaprol (BAL)

   Dimercaprol, also called British anti-Lewisite, binds the arsenic in lewisite and is given in the hospital. Hydroxocobalamin is the antidote for cyanide, not for an arsenic compound.

8. A blister agent that causes immediate, intense pain and hive-like wheals on contact, and is sometimes called an urticant, is:

   1. A. Sulfur mustard
   2. B. Chlorine gas
   3. C. VX nerve agent
   4. D. Phosgene oxime
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   Answer: D. Phosgene oxime

   Phosgene oxime (CX) produces instant pain and wheals that later become lesions, which sets it apart from painless mustard. Despite its name, it is a vesicant, not a choking agent like phosgene.

9. Workers exposed to phosgene at a sabotaged chemical plant have only mild eye irritation and feel fine. They ask to walk home. You should:

   1. A. Release them; their lungs are clear
   2. B. Have them walk to the ED to save units
   3. C. Keep them at rest and transport them
   4. D. Give albuterol and release them on scene
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   Answer: C. Keep them at rest and transport them

   Phosgene can cause pulmonary edema hours later, and physical exertion makes it worse, so exposed people should stay at rest and be observed. Clear lungs now do not rule out delayed injury.

10. Six hours after a sulfur mustard attack, a man's eyelids are swollen shut, and he cries out that he has gone blind. After gently irrigating his eyes, you should tell him that:

    1. A. His sight loss is likely permanent
    2. B. Forcing the lids open will save his sight
    3. C. The swelling shows agent still on the eye
    4. D. Most such eye injuries heal over weeks
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    Answer: D. Most such eye injuries heal over weeks

    Mustard often causes lid swelling and spasm (blepharospasm) that keep the eyes closed, so the patient cannot see even though the eye itself is usually not destroyed. Most mustard eye injuries recover over one to several weeks; severe corneal injury, which can take months, is less common, so reassurance is appropriate. Permanent blindness is rare. Forcing swollen lids open can injure the cornea and does not speed recovery. The delayed swelling is the tissue's reaction to injury that occurred at the time of exposure, not active agent still on the eye.

11. Terror groups have used chlorine as a weapon mainly because it:

    1. A. Has no odor and cannot be detected
    2. B. Causes no symptoms for hours
    3. C. Is easy to obtain from industry
    4. D. Is a potent nerve agent in vapor
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    Answer: C. Is easy to obtain from industry

    Chlorine is shipped and stored in large amounts for water treatment and industry, so it is easy to obtain. It has a strong bleach odor and causes immediate symptoms, so it is not an odorless, delayed agent.

12. Chlorine and phosgene are classed among chemical weapons as:

    1. A. Vesicants (blister agents)
    2. B. Pulmonary (choking) agents
    3. C. Metabolic (blood) agents
    4. D. Incapacitating agents
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    Answer: B. Pulmonary (choking) agents

    Pulmonary agents damage the airway and lungs, causing cough, bronchospasm, and pulmonary edema. Vesicants are tempting because chlorine can burn moist tissue, but vesicants are defined by skin blistering.

13. Hydrogen cyanide is a poor outdoor terror weapon mainly because it:

    1. A. Disperses rapidly in open air
    2. B. Has an odor that warns people
    3. C. Breaks down in sunlight in seconds
    4. D. Must be swallowed to cause harm
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    Answer: A. Disperses rapidly in open air

    Cyanide gas is lighter than air and spreads out quickly outdoors, so it is most dangerous in enclosed spaces. Many people cannot smell its bitter almond odor, so odor would not reliably warn victims.

14. After a cyanide gas release in a closed office, an employee walked out on her own. She is alert, and her headache and dizziness are fading. The best care is:

    1. A. Immediate RSI to protect her airway
    2. B. Sodium nitrite before she worsens
    3. C. Release after 15 minutes of watching
    4. D. Oxygen, monitoring, and transport
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    Answer: D. Oxygen, monitoring, and transport

    Victims who escape cyanide gas and are improving usually need only oxygen, monitoring, and evaluation; antidotes are reserved for those with serious signs. Release on scene is wrong because she still needs evaluation for a significant exposure.

15. Cyanogen chloride differs from hydrogen cyanide because it also:

    1. A. Blisters the skin after hours
    2. B. Irritates the eyes and airway
    3. C. Inhibits acetylcholinesterase
    4. D. Is absorbed mainly through the skin
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    Answer: B. Irritates the eyes and airway

    Cyanogen chloride (CK) releases cyanide in the body and also acts as a strong irritant to the eyes, nose, and lungs. It does not inhibit acetylcholinesterase; that is the action of nerve agents.

16. In most healthy people, the effects of CS tear gas:

    1. A. Last for several days without treatment
    2. B. Must be reversed with atropine injections
    3. C. Fade within about 30 minutes in fresh air
    4. D. Cause skin blisters about 12 hours later
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    Answer: C. Fade within about 30 minutes in fresh air

    CS causes intense but brief tearing, burning, and coughing that usually resolve within about 30 minutes once the person reaches fresh air. Atropine is tempting because of the tearing and secretions, but these agents are irritants, not cholinergic poisons.

17. Riot-control agents can cause serious harm, such as severe bronchospasm, mainly in:

    1. A. People with asthma in enclosed spaces
    2. B. Healthy adults exposed out in the open
    3. C. People exposed for under a minute
    4. D. People who wear eyeglasses
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    Answer: A. People with asthma in enclosed spaces

    High concentrations in closed spaces and underlying lung disease such as asthma or COPD raise the risk of serious airway effects. Healthy adults in open air usually recover fully with fresh air.

18. OC (pepper spray) causes its effects by:

    1. A. Blocking acetylcholinesterase in nerves
    2. B. Releasing chlorine on moist tissue
    3. C. Binding cytochrome oxidase in cells
    4. D. Inflaming nerve endings with capsaicin
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    Answer: D. Inflaming nerve endings with capsaicin

    Oleoresin capsicum contains capsaicin, which stimulates pain receptors and causes burning, tearing, and swelling of the mucous membranes. Cytochrome oxidase binding is the action of cyanide.

19. After a tear gas release in a subway, several victims are loaded into your ambulance. Your crew begins coughing en route because:

    1. A. The agent is contagious between people
    2. B. Agent on their clothing keeps off-gassing
    3. C. Their own exposure at the scene is just now showing
    4. D. Victims are exhaling the agent they inhaled
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    Answer: B. Agent on their clothing keeps off-gassing

    Riot-control particles cling to clothing and hair and continue to irritate in a closed compartment, so outer clothing is removed and the unit is ventilated. These agents are chemicals, not infections, so they are not passed between people. Tear gas acts within seconds, so a crew that felt fine at the scene is not having a delayed reaction, and victims do not breathe out meaningful amounts of the particles they inhaled.

20. A BZ release leaves victims hot, dry, flushed, and delirious with dilated pupils. Compared with nerve agent casualties, they:

    1. A. Usually recover over hours to days
    2. B. Need atropine and pralidoxime at once
    3. C. Die within minutes without an antidote
    4. D. Develop blisters on the skin by morning
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    Answer: A. Usually recover over hours to days

    BZ is an incapacitating anticholinergic agent; with sedation, cooling, and fluids, victims recover over hours to days, and physostigmine may be used in the hospital. Atropine would worsen the anticholinergic picture, which is the opposite of nerve agent care.

21. In 2002, Russian forces pumped an aerosolized fentanyl derivative into a Moscow theater to end a hostage crisis, and many hostages died. Survivors of such an exposure need:

    1. A. Atropine and pralidoxime
    2. B. Hydroxocobalamin and oxygen
    3. C. Airway support and naloxone
    4. D. Eye irrigation and fresh air
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    Answer: C. Airway support and naloxone

    Opioid-based incapacitating agents cause respiratory depression, so ventilation and naloxone are the key treatments; many deaths came from airway obstruction and apnea. Atropine and pralidoxime treat nerve agents, which cause secretions and twitching rather than opioid apnea.

22. Attackers deliberately rupture a rail tank car of anhydrous ammonia near a neighborhood. Among terrorism threats, ammonia is classed as a:

    1. A. Military-grade nerve agent
    2. B. Toxic industrial chemical
    3. C. Biologic toxin
    4. D. Radiologic material
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    Answer: B. Toxic industrial chemical

    Toxic industrial chemicals such as ammonia and chlorine are produced and moved in huge amounts, making them attractive targets for sabotage. Ammonia is a corrosive gas, not a nerve agent or toxin.

23. Field care of the skin lesions caused by sulfur mustard is much like the care of:

    1. A. Snakebite, with a constricting band
    2. B. Frostbite, with rapid rewarming
    3. C. Partial-thickness burns
    4. D. Cellulitis, with warm moist soaks
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    Answer: C. Partial-thickness burns

    Mustard lesions are covered with clean dry dressings and treated like partial-thickness burns, though they usually need less fluid than thermal burns of the same size. Warm soaks and rewarming are not used and can deepen tissue injury.

24. Field decontamination of a patient with liquid mustard on the skin is best done with:

    1. A. Large amounts of soap and water
    2. B. Dry wiping with alcohol
    3. C. Undiluted household bleach on skin
    4. D. Vinegar rinse to neutralize the agent
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    Answer: A. Large amounts of soap and water

    Prompt, thorough washing with soap and water removes liquid vesicant; dilute hypochlorite may be used on equipment by trained teams. Undiluted bleach injures skin and is not used on patients.

25. Compared with sarin, sulfur mustard is more persistent, which means it:

    1. A. Acts faster after it is inhaled
    2. B. Is far more lethal drop for drop
    3. C. Spreads farther on the wind
    4. D. Stays in the environment longer
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    Answer: D. Stays in the environment longer

    Persistent agents such as mustard and VX remain on surfaces and in soil for days, posing contact hazards long after the release. Sarin is far more lethal per drop, which is why that distractor is wrong for mustard.