Treatment techniques for patients exposed to riot control agents.
Overview:
Riot control agents are non-lethal chemical compounds that are used to incapacitate exposed individuals via intense irritation of the airway, respiratory tract, eyes and skin.[1,2,3] These agents have been used as crowd control agents by law enforcement during protests, riots or civil unrest. These agents are also readily available to the public online with a variety of distribution mechanisms such as spray cans, handheld sprays and spray guns. The majority of the agents found online are referred to as “tear gas” or “pepper spray,” however it does not always identify the exact agent.
In general, these compounds are crystallized solids with low vapor pressures that can be aerosolized and released into the air via droplets or small particles. These particles or droplets then cause local irritation to mucosal membranes and skin or the airways/pulmonary system through inhalation.[2,3]
Clinical effects can occur within seconds and are generally transient, resolving within 30 minutes.[3] Prolonged exposure or exposure to a large dose, especially in a closed environment, has been associated with more severe effects, including burns, laryngospasm and chemical pneumonitis. Death is rare.[2,3]
Table 1: Specific Agents and their Characteristics Overview
| Agent | Agent Specific Characteristics | Mechanism of Action | Onset of Action |
Duration |
Agent Specific Effects |
|
1-Chloroacetophenone (CN)
O-Chlorobenzylidene malononitrile (CS)
Dibenz [b,f]-1,4-oxazepine (CR)
|
• CN is known as Chemical Mace. Formerly used as handheld spray, but has been replaced by CS.
• CS is used as tear gas by law enforcement in the U.S. • CR is used abroad in water cannons, smoke grenades and handheld spray cans. |
• Alkylating agents that act on nucleophilic sites on sulfhydryl-containing enzymes, transiently inactivating co-enzymes in the pyruvate decarboxylase system, causing tissue injury. (2)
• Release Bradykinin, causing pain. (2) |
• Seconds to minutes | • Usually < 30 minutes | • Potency:
CR > CS > CN (4) • Toxicity: CN > CS > CR • CN has the highest risk of systemic toxicity and can cause pulmonary injury, second degree burns, and increased risk of death, particularly with high doses used in an enclosed space. (2,5)
|
| Oleoresin capsicum (OC):
Trans-8-methyl-N-vanillyl-6-noneamide
|
• Known as Pepper Spray
• Predominately used in canisters, but also can be used as projectile fired from paintball guns. • Most commonly used agent by civilians and law enforcement. • Naturally occurring lacrimator, extracted from cayenne pepper plants, Capsicum annum. (3) |
• Binds transient receptor potential vanilloid type-1 ion channel (TRPV1), a heat dependent nociceptor. (3)
• Releases substance P, a neuropeptide that acts as a mediator of pain transmission (3) |
• Seconds to minutes | • Usually < 30 minutes. | • People who regularly eat hot peppers or regularly use capsaicin in pain relieving ointments are less susceptible to the pain associated with pepper spray. (2) |
| Diphenylaminearsine (DM) | • Odorless, yellow compound that is an aromatic and alkyl derivative of arsenic trichloride.
• Banned internationally as riot control and chemical warfare agent. |
• May exhibit anticholinesterase activity, but the mechanism is not well understood (6) | • 2 – 4 minutes (2) | • Up to 12 hours (2) | • Because of its slower onset of action, absorption can occur before warning symptoms, and unaware individuals can incidentally absorb a larger dose. (2)
• More significant GI effects (abdominal cramps, nausea, vomiting, diarrhea) • Death from pulmonary damage has occurred. |
| Chloropicrin (PS):
Trichloronitromethane
Nitrochloroform |
• Fumigant and soil insecticide that acts as a lacrimator. (2)
• Not authorized for military use anymore. Within the U.S., it is authorized as a pesticide. (9) |
• Not well understood, but it is thought to inhibit pyruvate dehydrogenase and succinate dehydrogenase. (7,8) | • Seconds to minutes. | • Respiratory and ocular symptoms usually resolve within 30 minutes
• GI symptoms may last for weeks and neurological symptoms can persist up to months after exposure. (9) |
• With moderate/severe exposure, can cause pulmonary edema, skin blisters, vomiting, dizziness, headaches.
• Cases of death secondary to pulmonary edema. (8)
|
Table 2: Clinical Effects & Management (2,10,11)
| Organ | Effect | Management |
| Eyes | • Lacrimation
• Conjunctiva injection/conjunctivitis • Blepharospasm • Sensation of blindness despite normal visual acuity • Corneal abrasions |
• Copious water/saline irrigation with Morgan Lens or nasal cannula
• Complete ophthalmologic exam, including slit lamp exam • Rarely causes permanent eye damage unless source of injury was a blast force from a weapon at close range |
| Skin | • Erythema
• Burning sensation • Blisters • Contact dermatitis, particularly with freshly shaved skin or recently abraded skin
|
• Erythema subsides 45-60 minutes after exposure
• Decontamination with soap and water • Local wound care • Consider updating tetanus if blistering |
| Airway/
Respiratory tract |
• Burning sensation
• Sneezing • Increased salivation • Coughing • Rhinorrhea • Laryngospasm • Bronchospasm • Chest tightness • Chemical pneumonitis |
• B2-agonists for bronchospasm
• Steroids if acute COPD/asthma exacerbation • CXR if severe exposure and concern for pneumonitis • Supplementary oxygen as needed |
| Cardiovascular | • Transient increase in heart rate and blood pressure | • Can cause adverse effects in patients with pre-existing cardiovascular disease |
| Gastrointestinal | • Nausea and vomiting with prolonged exposures
|
• Anti-emetics
• IVF resuscitation if needed |
Decontamination:
- Initial management involves removing the patient’s clothing and copious irrigation of the affected area with soap and water to remove irritants.
- Ophthalmologic irrigation with saline/water. Ophthalmology follow up for any abnormalities on examination.
- Healthcare providers should wear PPE when caring for these patients to avoid secondary contamination and exposure.
- Limited evidence for decontamination with milk, aluminum hydroxide-magnesium hydroxide (Maalox®), lidocaine gel, or baby shampoo.
- No significant pain difference among these decontamination techniques versus water.[12]
Management Overview:
- There is no antidote for these agents.
- Mainstay of treatment is decontamination, symptomatic relief and supportive care.
- Remember to consider projectile or blunt trauma injuries upon patient presentation and manage accordingly.
Safety Considerations to Provide for Patients Involved in Protests:
- Avoid wearing contacts if possible, glasses are preferred in the event of chemical exposure.
- Consider wearing goggles or a facemask for protection from chemical exposures.
- Long sleeve shirts/pants are encouraged to limit sun/chemical exposures.
- Bring a change of clothes; if exposed to riot control chemicals, remove initial clothing and place inside sealed plastic bag.
- Decontaminate chemical agents from your skin with large amounts of soap and water.
- Remember to stay hydrated and use sunscreen.
References
- Schep, L., Slaughter, R., & McBride, D. (2013). Riot control agents: the tear gases CN, CS and OC—a medical review. Journal Of The Royal Army Medical Corps, 161(2), 94-99. https://doi.org/10.1136/jramc-2013-000165.
- US Army Medical Research Institute of Chemical Defense, Chemical Casualty Care Division. (2007). Medical Management of Chemical Casualties Handbook.4th Aberdeen Proving Ground, MD; 194-211. http://www.globalsecurity.org/wmd/library/policy/army/other/mmcc-hbk_4th-ed.pdf.
- Suchard, J.R. (2019) Chemical Weapons. Nelson LS, Howland M, Lewin NA, Smith, SW, Goldfrank LR, Hoffman, RS. Eds.’ Goldfrank’s Toxicologic Emergencies, 11th Ed. New York, NY: McGraw-Hill. 1741 – 1752.
- Blain, P.G. (2003). Tear gases and Irritant Incapacitants. Toxicol Rev., 22(2):103‐110. https://doi.org/10.2165/00139709-200322020-00005
- Malhotra, R.C., Kumar, P. (1987). Chemistry and Toxicity of Tear Gases. Defence Science J., 37(2): 281-296. https://doi.org/10.14429/dsj.37.5910
- Acute Exposure Guideline Levels: Chloroarsenicals. (2007) US. Environmental Protection Agency. Retrieved 10 June 2020, from https://www.epa.gov/sites/production/files/2014-09/documents/chloroarsenicals_interim_11_2007.v1.pdf.pdf
- Sparks, S.E., Quistad, G. B., & Casida, J. E. (1997). Chloropicrin: reactions with biological thiols and metabolism in mice. Res. Toxicol., 10: 1001–1007.
- Acute Exposure Guideline Levels: Chloropicrin. (2008). US. Environmental Protection Agency. Retrieved 10 June 2020, from https://www.epa.gov/sites/production/files/2014-08/documents/chloropicrin_interim_0.pdf
- Chloropicrin (PS): Lung Damaging Agent. (2011). National Institute for Occupational Safety and Health. Emergency Response Safety and Health Database. Retrieved 9 June 2020 from https://www.cdc.gov/NIOSH/ershdb/EmergencyResponseCard_29750034.html
- Fisher, W. (2020). com. Retrieved 4 June 2020, from https://www.procedurettes.com/eye-irrigation.
- The Morgan Lens for emergency eye irrigation. Youtube. (2020). Retrieved 4 June 2020, from https://www.youtube.com/watch?v=ig_W9tkH5Bw.
- Barry, J.D., Hennessy, R., & McManus, J. (2008). A Randomized Controlled Trial Comparing Treatment Regimens for Acute Pain for Topical Oleoresin Capsaicin (Pepper Spray) Exposure in Adult Volunteers. Prehospital Emergency Care, 12(4): 432-437. https://doi.org/10.1080/10903120802290786
- Danoff, J, Kim, H. (2020). UMEM Educational Pearls: Riot Control Agents. Retrieved 4 June 2020, from https://em.umaryland.edu/educational_pearls/3764/.