CLINICAL REVIEW For the full versions of these articles see bmj.com Management of the effects of exposure to tear gas Pierre-Nicolas Carron, Bertrand Yersin Service of Emergency Medicine, Despite the frequent use of riot control agents by Eur- solvent, and delivered with a dispersion vehicle (a University Hospital Center and opean law enforcement agencies, limited information pyrotechnically delivered aerosol or spray University of Lausanne, 1011 exists on this subject in the medical literature. The solution).45 Tear gases are not currently considered as Lausanne CHUV, Switzerland Correspondence to: P-N Carron effects of these agents are typically limited to minor chemical weapons by Western countries. Since the [email protected] and transient cutaneous inflammation, but serious 1950s, they have been mainly used by law enforcement complications and even deaths have been reported. agencies for crowd control purposes in most European Cite this as: BMJ 2009;338:b2283 doi:10.1136/bmj.b2283 During the 1999 World Trade Organisation meeting countries, including the United Kingdom, France, and at the 2001 Summit of the Americas in Quebec, Germany, and Switzerland. Tear gases are also used exposure to tear gas was the most common reason for in military training exercises to test the rapidity or effi- medical consultations.12 Primary and emergency care cacy of protective measures in the event of a chemical physicians play a role in the first line management of attack. patients as well as in the identification of those at risk of Of the known disabling chemical irritants (of which complications from exposure to riot control agents. In there are more than a dozen), the five that are tradition- 1997 the National Poisons Information Service in Eng- ally used in the European Union are chlorobenzyli- land received 597 inquiries from doctors seeking dene-malononitrile (also known as CS, after the advice about problems related to crowd control.3 Our chemists Corson and Stoughton who first synthesised article reviews the different riot control agents, includ- it), chloroacetophenone (CN or “Mace”), dibenzoxa- ing the most common tear gases and pepper sprays, zepine (CR), oleoresin capsicum (OC), and pelargonic and provides an up to date overview of related medical acid vanillylamide (PAVA) (figure). 6 Diphenylamino- sequelae. chloroarsine (DM or adamsite) is an irritating and har- assing arsenic based agent used in some countries Sources and selection criteria outside the EU. Oleoresin capsicum is a mixture of We searched the following resources for relevant infor- cayenne pepper extracts, of which capsaicin is the mation on the medical toxicity and management of main active ingredient. 47 Its concentration varies acute exposure to tear gas and pepper spray: Medline, from 1% to 15% depending on the mixture. 7 Pepper PreMedline, Embase, CINAHL, SCIRUS, the strength is measured in Scoville heat units, ranging Cochrane Library, ISI Web of Knowledge, Toxnet, from zero for green pepper to 15 million units for pure Google Scholar, and personal archives. We used the capsaicin. 8 Pelargonic acid vanillylamide is a new stan- “ ” “ ” subject headings riot control agents , pepper spray , dardised synthetic variant of oleoresin capsicum used “ ” “ ” “ ” “ lacrimator , tear gas , irritants , incapacitating mainly in Switzerland, Austria, and Germany. 67 agents”, as well as the toxicological terms “chloro- benzylidene-malononitrile”, “chloroacetophenone”, “dibenzoxazepine”, “chlorodiphenylarsine” and “cap- saicin”. We also searched the reference lists for addi- tional articles. The overall evidence supporting the current therapeutic approach to patients exposed to tear gas or pepper spray is of poor quality. What is a tear gas? Tear gases (along with pepper sprays, toxic emetics, and some sedative substances) are among the so called riot control agents.4 A tear gas is actually not a gas at all, but a toxic chemical irritant in the form of powder or Use of tear gas at demonstration at the time of the 2003 G8 drops mixed to variable concentrations (1-5%) in a summit, Lausanne, Switzerland 1554 BMJ | 27 JUNE 2009 | VOLUME 338 CLINICAL REVIEW Cl O H TIPS FOR NON-SPECIALISTS CCCl Medical teams should wear protection for their own CCCN H safety and to prevent secondary contamination HNC Contaminated clothes must be removed; eyes and 2-chlorobenzylidene- 1-chloroacetophenone (CN) affected skin surfaces should be cleaned with water malononitrile (CS) Forpersistentocularsymptoms,ophthalmological Cl assessment is recommended O As For severe pulmonary symptoms, oxygen therapy, β2-mimetics and ipratropium aerosols may be required N C N For pulmonary symptoms, a 24-48 hour stay in H H hospital or a discharge home with detailed Dibenzoxazepine (CR) Diphenylaminochloroarsine (DM) H3CO CH 3 humidity.4 Characteristics common to all agents HO CH2 NH CO(CH2)4 CH CH C CH3 include a rapid onset time and a short duration of H effects, as well as a wide margin of safety between the Capsaicin incapacitating dose (ICt 50, the concentration (C) that causes incapacitation (I) in 50% of individuals after one = Chemical structure of riot control agents minute (t time)) and the lethal dose (LCt 50, the con- centration that causes death (L) in 50% of individuals after one minute).4 The agents differ from one another How do riot control agents work? by their duration of action, their toxicity (chloroaceto- The irritant effects of crowd control agents probably phenone and diphenylaminochloroarsine are more result from the action of chlorine or cyanide groups toxic than chlorobenzylidene-malononitrile or diben- in addition to alkalising compounds (figure). These zoxazepine), and their physical and chemical charac- agents interact with muco-cutaneous sensory nerve teristics (table 1). Current information on toxicity is receptors such as TRPA1 cation channels. 9 The effect largely based on in vitro and animal studies. 4 of oleoresin capsicum is linked to a direct stimulation of type C and Aδ sensory nerve endings, provoking an What are the medical consequences of acute exposure immediate release of the inflammatory P substance. 78 to tear gas and pepper spray? A toxic effect of the solvent methyl-isobutyl-ketone or of certain metabolites has also been documented in There is limited human research on the risks of tear gas animal experimental studies, in particular for chloro- in terms of inducing disability or death. The irritant benzylidene-malononitrile (formation of cyanide and effect of tear gases affects exposed cutaneous and thiosulfate derivatives) and chloroacetophenone (for- mucous membrane surfaces.45 Table 2 summarises mation of hydrogen chloride).71011 the medical complications. Clinical experience and Assessments of the effects of riot control agents must retrospective case studies suggest that the cutaneous take into account the weather (wind, rain, and ambient effect is by far the most serious symptom, including temperature) in addition to the characteristics of the first and second degree burns. 12 13 Even in minor site of deployment (open or closed space) as the effects cases, skin erythema can last several hours. Direct con- of tear gas are enhanced by heat and by high ambient tact with the flame or a hot canister increases the risk of Table 1 | Physical and chemical characteristics of tear gases and pepper spray 47 Time to Duration of action Relative ICt 50 LCt 50 Name Characteristics activation (minutes) potency* (mg/min per m3)† ‡ (mg/min per m3) Chloroacetophenone Apple odour; powder or emulsion; aerosol 3-10 seconds 10-20 1 20-50 8500-25 000 Chlorobenzylidene malononitrile Pepper odour; microparticles; dispersing 10-60 seconds 10-30 5 4-20 25 000-100 000 effect (grenades) Dibenzoxazepine Odourless; aerosol; persists for prolonged Instantaneous 15-60 20-50 0.2-1 >100 000 periods in the environment or on clothes Diphenylaminochloroarsine Odourless or slightly bitter almond odour; Rapid >60 0.5-2 50-100 10 000-35 000 emetic Oleoresin capsicum Pepper odour; persists for prolonged Rapid 30-60 Not applicable Not applicable >100 000 periods in the environment or on clothes; short distance spray *Refers to the irritant effect. †ICt 50=the concentration that causes incapacitation in 50% of individuals after one minute. *LCt 50=the concentration that causes death in 50% of individuals after one minute. BMJ | 27 JUNE 2009 | VOLUME 338 1555 CLINICAL REVIEW pulmonary oedema has been described in recent case 47 Factors influencing the effect of exposure to tear gas studies, but permanent long term lung damage seems Pre-existing conditions and characteristics of the improbable.19 20 Several cases of death have been affected person attributed to the use of chloroacetophenone in con- Asthma fined spaces. Some of the deaths in the 1993 siege on Chronic obstructive pulmonary disease the Branch Davidians in Waco, Texas, were attributed Cardiovascular disease to the use of large amounts of chlorobenzylidene- malononitrile in a confined space.57 Severe hypertension With pepper sprays, the irritant effect is immediate Young children and lasts 30 minutes on average, mainly affecting the Patients over 60 years eyes, skin, and respiratory tract.17 21 Minor side effects Ocular diseases (corneal erosion, respiratory irritability) are described Contact lenses in many case reports.22 The rare deaths that have been Environmental factors documented were caused by bronchospasm, pulmon- ary oedema, or respiratory arrest and occurred mainly Confined space in patients with asthma.6717