Riot Control Agent

Aka: Riot Control Agent, Tear Gas, Lacrimogenic gas, Oleoresin of Capsicum, Pepper Spray, Chlorobenzylidenemalononitrile, Chloroacetophenone, Chlorodihydrophenarsazine, Mucosal Irritant

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II. Definitions

  1. Riot Control Agent (e.g. Tear Gas)
    1. Aerosolized powders used by police and military to suppress crowds by causing eye, skin and nose irritation
    2. Dispersed via handheld atomizer or paintballs

III. Causes: Common Riot Control Agents

  1. Commonly used Riot Control Agents
    1. Oleoresin of Capsicum (OC, Pepper Spray)
      1. Oily concentrated Capsaicin extract from chili peppers (e.g. jalapenos)
      2. Scoville units may approach 2,00,000 (contrast with jalapenos, Scoville 2000)
    2. Chlorobenzylidenemalononitrile (CS) Powder
      1. Most common agent used in U.S. by police and border control agents (developed 1928)
      2. Has replaced CN, due to less toxicity and less severe systemic toxicity
      3. Half life for CS and metabolites: 5 to 660 seconds (11 minutes)
    3. Chloroacetophenone (CN, Tear Gas, mace)
      1. More skin irritation than with CS
  2. Older agents with greater toxicity and potency
    1. Chlorodihydrophenarsazine (DM)
    2. Dibenzoxazepine (CR) Gas

IV. Mechanism

  1. All agents activate the TRPA1 pain receptors, causing irritation and inflammation at skin, eye, nose
  2. Substance P and CGRP are also released
  3. Riot Control Agent exposure to CN or CS is rarely lethal unless in enclosed spaces
  4. Mucosal Irritants are dissolved in solvents, allowing for aerosolization
    1. Solvents may also be associated with specific toxicity

V. Findings: Signs and Symptoms

  1. Eye
    1. Eye tearing (Lacrimation)
    2. Conjunctivitis
    3. Chemosis
    4. Blepharospasm
    5. Eyelid Edema
  2. Nose
    1. Nasal congestion
    2. Rhinorrhea
  3. Lung
    1. Cough
    2. Bronchospasm
    3. Hemoptysis
    4. Copious airway secretions
    5. Exacerbation of Asthma, COPD or other chronic lung disease
  4. Gastrointestinal
    1. Nausea and Vomiting
  5. Skin
    1. Skin burning Sensation
    2. Contact Dermatitis (uncommon)
    3. Skin bullae (prolonged exposure)

VI. Pharmacokinetics

  1. Onset of ocular and respiratory symptoms: 20 to 60 seconds after exposure
  2. Ocular irritation duration: 10-30 minutes (photophobia may persist)
  3. Contact Dermatitis or skin bullae duration: 4 days

VII. Management

  1. Preparation
    1. All rescuers should wear Personal Protective Equipment (PPE, Eye Protection, masks, gowns)
  2. Decontamination
    1. Evacuate patient to open, fresh air
    2. Remove all contaminated clothing
    3. Wash all skin with soap and water (remove all traces of chemical)
    4. Eye Irrigation for 15 minutes
    5. Consider Diphoterine Wash (Decontamination and chelating solution)
  3. ABC Management
    1. Airway Management
    2. Supplemental Oxygen as needed
    3. Oral secretion and nasal secretion suctioning
    4. Acute bronchospasm management (e.g. AlbuterolInhaler or Nebulized Albuterol)
  4. Contact Dermatitis Management
    1. Wash intact exposed skin with soap and water
    2. Irrigate broken skin with saline
    3. Burn Management as needed
  5. Eye exposure
    1. Irrigation with water of saline for 10-15 minutes if symptoms present
    2. Complete Eye Injury exam (Slit Lamp, Fluorescein stain)

VIII. Complications: Rare but Serious (depending on agent used)

  1. Respiratory complications (rare)
    1. Pulmonary Edema
    2. Reactive Airway Dysfunction Syndrome
  2. Ocular complications
    1. Hyphema
    2. Uveitis
    3. Necrotizing Keratitis
    4. Traumatic optic Neuropathy
  3. Blunt Trauma and Thermal Burns from delivery device impacts
    1. Significant burn injuries
    2. Limb Amputations or functional loss
    3. Permanent Vision Loss

IX. Prevention

  1. Limit exposure to mucosal agents (immediately leave areas where irritants are dispersed)

X. Resources

  1. CDC Riot Control Agents
    1. https://emergency.cdc.gov/agent/riotcontrol/factsheet.asp

XI. References

  1. Tomaszeski (2020) Crit Dec Emerg Med 34(6): 32
  2. Vedula and Jasani (2025) Crit Dec Emerg Med 39(5): 4-14
  3. Olajos (2001) J Appl Toxicol 21(5):355-91 +pmid:11746179 [PubMed]
  4. Schep (2015) J R Army Med Corps 161(2):94-9 [PubMed]

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