AUTHOR AND EDITOR INFORMATION

Section 1 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

INTRODUCTION

Section 2 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Background

The sole purpose of irritants, also known as tear gas, riot control agents, and lachrymators, is to produce immediate discomfort and eye closure to render the victim incapable of fighting or resisting. Police forces use them for crowd control, and military forces currently use them mainly for training. They were used before World War I, and, during the war, they were the first chemical agents used—well before the better-known chlorine, phosgene, and mustard gas. The United States used them during the Vietnam War to deny tunnel access to its enemies. The United States excludes these agents from the 1925 Geneva Convention banning other chemical and biological weapons. Dispersal is allowed in specific US military operations but only by presidential order.

Tear gas (CS) and chloroacetophenone (CN) are by far the most important pulmonary irritants. These types of compounds were assigned these 2-letter codes by The North Atlantic Treaty Organization (NATO). CN was the primary pulmonary irritant after World War I until Corson and Stoughton developed CS in 1928. CS was found to be more potent (10 times more potent as a lachrymator than CN) but less toxic. In approximately 1959, CS replaced CN as the principal military and law enforcement riot control agent. CS gas is the familiar tear gas most often used by police for crowd control (eg, the police in the United Kingdom have used CS as an incapacitant for the past decade). CN is available as Mace, an over-the-counter product used for personal protection. Capsaicin, or pepper spray, has to some extent replaced CN as a personal protective agent, with less dangerous effects.

Although CS and CN are the most important agents in this class, several others require mention. Chloropicrin (PS) and bromobenzenecyanide (CA) were developed before World War I. Both largely have been replaced, as they were too lethal for their intended effects but not lethal enough to compete with the more effective blistering and nerve agents. PS is still seen occasionally as a soil sterilant or grain disinfectant. The creation of CNB (CN, carbon tetrachloride, and benzene), chloroacetophenone in chloroform (CNC), and CNS (CN, chloroform, and PS) attempted to make CN more effective. However, CS proved more effective and less toxic than any of the CN series and largely has replaced them.

Dibenz-(b,f)-1,4-oxazepine (CR) is a more recent tear gas, first synthesized in 1962. It reportedly is more potent and less toxic than CS. Part of its high safety profile is due to its low volatility, which minimizes its effects deep in the pulmonary system. However, it is still is not used widely. Pepper spray, or oleoresin capsicum (OC), is also considered a riot control agent. A 1% solution is sold commercially to the public, but solutions exist that have a 10% concentration. OC causes the release of a neuropeptide (substance P) that causes pain and inflammation.

Pathophysiology

Riot control agents are solids with low vapor pressures that are dispersed as fine particles or in solution. CS and CN are SN₂ alkylating agents and react at nucleophilic sites. Although presently unclear, injuries caused by this class of agents may be caused by inactivation of sulfhydryl-containing enzymes such as lactic dehydrogenase and a specific coenzyme in the pyruvate decarboxylase system (disulfhydryl form of lipoic acid).

CLINICAL

Section 3 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

History

• Most pulmonary irritant exposures are self-limited. Onset of symptoms occurs in seconds to several minutes. Duration is 15-30 minutes after clothing is removed and the patient is in an open space. Reconsider the diagnosis of riot control agents if symptoms persist longer than 30 minutes. However, in one recent study, the majority of subjects who were directly sprayed with CS in the face still had respiratory and oral symptoms after 1 hour.¹
• Typically, the eyes, nose, mouth, and even airway feel a burning sensation.
• The eye is the most sensitive organ involved and is the most immediate and severely affected of all the target organs.
• • Ocular pain, tearing, and severe blepharospasm are common.  At high concentrations, CN is known to cause corneal epithelial damage and chemosis.
  • Conjunctival injection and periorbital edema may be noted.
  • More serious and even permanent eye injuries (eg, corneal abrasions, foreign bodies) can occur. Tear gas particles, other foreign particles, or the blast injury itself causes these injuries.
  • Patients may complain of blindness because of the intense tearing and blepharospasm, but patients who can physically open their eyes have no significant change in visual acuity.
  • Nausea, vomiting, and diarrhea may also occur.
• Rhinorrhea, sneezing, and hypersalivation often occur as agents come in contact with sensitive mucous membranes.
• Patients also may report cough, chest tightness, dyspnea, and wheezing, but pulmonary function test results typically are not changed. These agents can exacerbate a chronic pulmonary condition such as asthma or chronic obstructive pulmonary disease.
• Cardiovascular function may demonstrate an increased blood pressure and heart rate, but this effect is believed to be most likely a psychological response to the situations in which tear gases typically are used.
• Exercise exacerbates symptoms.
• Patients develop tolerance to tear gas symptoms with chronic low-grade exposures.
• Psychological effects (eg, anxiety) also provoke increased response.
• Once the skin comes in contact with a riot control agent, erythema, tingling, and burning occur. Blistering may also occur after exposure to higher concentrations. These symptoms occur within minutes of exposure and last up to 1 hour after termination of exposure.
• • More severe skin injuries can occur in hot, humid environments with heavily sweating or wet patients or with prolonged or close-range exposures.
  • Patients can develop first- or second-degree burns, and delayed allergic contact dermatitis may be seen especially with exposure to CN and CS.  
  • Police and by-standers may be unintended victims of riot control agents. In one study by Watson et al, 6 police officers and 1 bystander developed contact dermatitis, leukoderma, exacerbation of seborrheic dermatitis, and aggravation of rosacea following exposure to CS.²
• Serious effects including death have been reported. CN has accounted for 5 deaths due to pulmonary injury and/or asphyxia. A case report involved a 4-week-old infant who accidentally received a discharge of pepper spray (OC), which immediately led to respiratory distress, followed by apnea. The infant was resuscitated and ultimately recovered after much intensive care, including extracorporeal membrane oxygenation (ECMO).³
• • Usually such effects (eg, pulmonary edema, chemical pneumonitis) only occur with the combination of prolonged exposure and use in an enclosed space.
  • Such exposures can damage the respiratory tree. Upper airway mucosal necrosis and pulmonary edema have been reported.
  • Some studies have suggested that CS may be converted into cyanide in the peripheral tissues. However, the risk of cyanide toxicity seems to be minimal.⁴
  • One animal study has demonstrated no adverse effects of CS during pregnancy.⁴
• Unintentional oral ingestions can occur, specifically in children.
• • Abdominal cramps and diarrhea are common, but the ultimate course usually is uneventful.
  • The lethal dose in one half of the exposed population (LD50) in animals is 200 mg/kg, which is an amount unlikely to be ingested.
• Other gases irritating to the mucous membranes and respiratory system (eg, lewisite, phosgene oxime) may be confused with pulmonary irritants.
• • A history of gas exposure in use by law enforcement or military training suggests tear gas use.
  • Eye symptoms are especially prominent in pulmonary irritant use.
  • Significant respiratory findings are rare but may occur in high concentrations in an enclosed space, especially in pediatric and geriatric victims with preexisting comorbidities.

DIFFERENTIALS

Section 4 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

WORKUP

Section 5 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Lab Studies

• Arterial blood gas measurements allow for confirmation of adequate ventilation.

Imaging Studies

• A chest radiograph may be indicated in patients with significant respiratory complaints, especially if the offending agent is not known.

Other Tests

• Perform a slit lamp examination with fluorescein on patients with significant eye complaints, especially if the patient experienced a close-range exposure.

TREATMENT

Section 6 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Prehospital Care

Most people exposed to pulmonary irritants do not seek medical care, and effects are self-limited.

• When patients seek care, first withdraw them from exposure. Then, decontaminate patients.
• • Acceptable decontaminating solutions are water or soap and water.
  • Do not use hypochlorite. This relatively caustic solution may worsen the condition of skin injuries already suffered from exposure to irritants.
  • Devote specific attention to very young, infirm, and elderly patients since their responses to these agents may be significant.
  • Warn patients that the pain worsens during decontamination.

Emergency Department Care

Initiate or continue care in the emergency department as discussed above.

• Proper personal protection equipment (PPE) should be donned in order to minimize accidental exposure.
• A site should be established for the disrobing and general decontamination of the patients.
• Flush the eyes of patients with eye complaints with normal saline or water to remove any particulate matter before fluorescein slit lamp examination for corneal abrasion.
• Treat more severe injuries, which occur in fewer than 1% of patients, in the usual fashion.
• Corneal abrasions can be treated with local antibiotics, oral analgesics, and close follow-up care.
• The rare eye foreign body may merit ophthalmologic consultation.
• Treat burns based on the severity and location of injury.
• The patient with significant respiratory damage is rare and may require oxygen supplementation, bronchodilator therapy (if bronchospasm is present), and admission to the hospital, possibly a critical care unit.

MEDICATION

Section 7 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

In general, only decontamination with water is necessary when a patient's skin has become grossly exposed. Bronchodilators, analgesics, and pulmonary support may be needed depending upon the severity of injury.

Drug Category: Bronchodilator

Use only for patients with evidence of significant bronchospasm after exposure.

Drug Category: Nonsteroidal anti-inflammatory agents (NSAIDs)

NSAIDs have analgesic, anti-inflammatory, and antipyretic activities. Their mechanism of action is not known, but they may inhibit cyclooxygenase activity and prostaglandin synthesis. Other mechanisms, such as inhibition of leukotriene synthesis, lysosomal enzyme release, lipoxygenase activity, neutrophil aggregation, and various cell-membrane functions, may exist as well.

Drug Category: Analgesics

Pain control is essential to quality patient care. Analgesics ensure patient comfort, promote pulmonary toilet, and have sedating properties, which are beneficial for patients who have sustained trauma or injuries.

Drug Category: Antibiotics

Therapy must cover all likely pathogens in the context of the clinical setting.

FOLLOW-UP

Section 8 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Further Inpatient Care

• Most patients can be discharged safely. The rare patient with significant respiratory findings may merit admission.

Prognosis

• The prognosis is excellent. The few reported dangerous effects occur rapidly.

Patient Education

• For excellent patient education resources, visit eMedicine's Bioterrorism and Warfare Center. Also, see eMedicine's patient education articles Chemical Warfare and Personal Protective Equipment.

MISCELLANEOUS

Section 9 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Medical/Legal Pitfalls

• Transporting a victim in an ambulance or a helicopter without proper decontamination, thereby exposing the crew to the effects of the agent.
• Failure to decontaminate victims properly.
• Failure to don proper PPE while decontaminating patients.
• Significant injuries, although rare, can occur with pulmonary irritant exposure. Screen patients for significant eye, skin, or respiratory injuries as discussed above.

REFERENCES

Section 10 of 10

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

1. Karagama YG, Newton JR, Newbegin CJ. Short-term and long-term physical effects of exposure to CS spray. J R Soc Med. Apr 2003;96(4):172-4. [Medline].
2. Watson K, Rycroft R. Unintended cutaneous reactions to CS spray. Contact Dermatitis. Jul 2005;53(1):9-13. [Medline].
3. Billmire DF, Vinocur C, Ginda M, Robinson NB, Panitch H, Friss H. Pepper-spray-induced respiratory failure treated with extracorporeal membrane oxygenation. Pediatrics. Nov 1996;98(5):961-3. [Medline].
4. Sam Shen. Riot-control agent attack. In: Ciottone GR, Anderson PD, Auf Der Heide E, Darling RG, Jacoby I, Noji E, Suner S, eds. Disaster Medicine. 3^rd ed. Philadelphia, PA: Mosby/Elsevier; 2006:Chap 98, 593-595.
5. Army, Marine Corps, Navy, Air Force. Military Chemical Compounds and Their Properties in Potential Military Chemical/Biological Agents and Compounds. January 2005. Available at www.mipt.org/pdf/Potential-Military-Chemical-Biological-Agents-Compounds.pdf. Accessed April 2, 2005.
6. Bentur Y, Gomez J. Incapacitating agents: BZ, calmative agents, and riot control agents. In: Keyes DC, Burstein JL, Schwartz RB, et al, eds. Medical Response to Terrorism, Preparedness and Clinical Practice. Philadelphia, PA: Lippincott Williams & Wilkins; 2005.
7. Blain PG. Tear gases and irritant incapacitants. 1-chloroacetophenone, 2-chlorobenzylidene malononitrile and dibenz[b,f]-1,4-oxazepine. Toxicol Rev. 2003;22(2):103-10. [Medline].
8. CDC. Brief report: exposure to tear gas from a theft-deterrent device on a safe--Wisconsin, December 2003. MMWR Morb Mortal Wkly Rep. Mar 5 2004;53(8):176-7. [Medline].
9. CDC. Riot Control Agent Poisoning. Centers for Disease Control and Prevention Web site. Available at www.bt.cdc.gov/agent/riotcontrol/agentpoisoning.asp. Accessed May 12, 2004.
10. Chemical Casualty Care Division USAMRICD. Medical Response to Chemical Warfare and Terrorism. 3^rd ed. i-iv, 73-79.
11. Compton JA. Tear agents. In: Military Chemical and Biological Agents. 1987:208-252.
12. Field Manual. Riot Control Agents. Treatment of Chemical Agent Casualties and Convention Military Chemical Injuries. Medical NBC Online Web site. Available at www.nbc-med.org/SiteContent/MedRef/OnlineRef/FieldManuals/fm8_285/Part_2/chapter7.htm. Accessed April 2, 2005.
13. Lillie SH, Hanlon E, Kelly JM, eds. Potential Military Chemical/Biological Agents and Compounds (FM3-11.9). 2005.
14. Nelson LS. Simple asphyxiants and pulmonary irritants. In: Goldfrank LR, Flomenbau NE, Lewin NA, eds. Goldfrank's Toxicologic Emergencies. Appleton & Lange; 1998:1523-1538.
15. Sidell FR. Riot control agents. In: Textbook of Military Medicine. Part 1. 1997:307-324.
16. USAMRICD. Riot Control Agents in Medical Management of Chemical Casualties Handbook. 3rd ed. USAMRICD. Available at: https://ccc.apgea.army.mil/sarea/products/handbooks/MMCC/mmccthirdeditionjul2000.pdf. July 2000.
17. Weir E. The health impact of crowd-control agents. CMAJ. Jun 26 2001;164(13):1889-90. [Medline].

Article Last Updated: Aug 9, 2007