NEWS

❙❙❙Public Health

The health impact of crowd-control agents

ome observers say that the civil dis- cians seeking advice about the manage- none (CN) and dibenzoxazepine (CR).2 obedience demonstrated in Quebec ment of patients who had been exposed At normal daily temperatures and S 1 City this April and in Seattle 2 years to crowd-control agents. Most en- pressure these agents form solid white ago represents merely the first wave of quiries concerned ocular (irritation, crystals; when used for a grassroots movement that is emerg- lacrimation, corneal abrasions), dermal they are dispersed as microparticulate (rash, erythematous dermatitis, blisters, ing to support the casualties of capital- clouds by pyrotechnic devices. To de- bullae, eczema, edema), respiratory ploy them as sprays, the use of propel- ism and globalization. If such dem- (coughing, dyspnea), neurologic lants and nonaqueous solvents, such as onstrations erupt locally, physicians (headache, drowsiness), cardiac (tachyp- the industrial degreaser methyl should be prepared to deal with the nea, hypotension, chest pain) and gas- isobutyl ketone, is required. Exposure clinical effects of crowd-control agents trointestinal (buccal irritation, vomit- to such solvents can by itself cause der- such as ; more than 5000 of ing) symptoms. mal scaling, peeling and blistering as these canisters were used against dem- Fifty-four people with dermal symp- well as irritation of the eyes and respi- onstrators in Quebec City during the toms who presented within 6 hours af- ratory tract.3 Summit of the Americas. ter exposure had erythema and irrita- tion, whereas 203 people with these Clinical management: CS, CN and CR Epidemiology: Data on injury patterns symptoms who sought treatment 6 gases irritate the skin, eyes and upper during social protests are scarce, since hours or more after exposure had blis- respiratory tact. They have been de- the fervour of protest can escalate rap- ters, bullae, eczema and edema. This scribed as chemical barbs4 that cling to idly and unexpectedly, making premedi- difference suggests that there may be moist mucous membranes. They cause tated, systematic data collection diffi- delayed adverse dermal effects to tear- lacrimation, excruciating pain, bleph- cult. Some insights can be gleaned from gas exposure. arospasm and conjunctival erythema data collated by the National Poison In- The agents most commonly used in upon eye exposure. Rhinorrhea and formation Service in England. In 1997 tear gas are o-chlorobenzylidene mal- nasal discomfort are common, as is a it received 597 enquiries from physi- ononitrile (CS), ω-chloroacetophe- stinging sensation in the mouth, accom-

CMAJ • JUNE 26, 2001; 164 (13) 1889 NNOUVELLESOUVELLES

panied by nausea and vomiting. These minated clothing.4 The ocular irrita- area downwind of the fan should be symptoms may by accompanied by a tion typically lasts only 15 minutes but vacant to avoid secondary contamina- sore throat, sneezing, coughing, chest may persist up to 3 days. If the charge tion. Others recommend irrigation tightness and increased salivation.2 of tear gas is fired at close range, pow- with normal saline. Persistent ocular Symptom onset occurs within 20 to der infiltration of the conjuctiva, irritation is usually the result of a par- 30 seconds after exposure and usually corneas and sclera may occur. Re- ticle of CS embedded in the surface, so stops in 10 to 30 minutes if the ex- ported complications include symble- a thorough slit-lamp examination posed individual stays outside, ideally pharon, infective keratitis, hyphema should be conducted. facing the wind, and removes all conta- and vitreous hemorrhage.5 Delayed dermal effects have also been reported. Prevention: Current evidence suggests CS gas can cause erythematous der- that tear-gas exposure is not dangerous matitis and contact dermatitis with to most people.4 Exposure may trigger blisters, vesicles and crusts. This is of- laryngospasm or bronchospasm in peo- ten accompanied by marked edema; ple with pre-existing respiratory disease, onset takes place between 12 hours and such as asthma or bronchitis, and they 3 days after exposure. Skin that is ex- are best advised to avoid voluntary ex- posed to CR gas may become ex- posure. Allergic contact dermatitis from tremely painful upon contact with wa- repeated exposure to chemical-based ter for up to 48 hours. CN gas may control agents has been identified in sensitize the skin and can produce al- both law-enforcement officers and lergic contact dermatitis within 72 demonstrators at protests.7 Susceptible hours after exposure.2 individuals should avoid repeated expo- If a person has been exposed to tear sure. — Erica Weir, CMAJ gas, contaminated clothing should be removed and sealed in a plastic bag to References 1. Wheeler H, MacLehose R, Euripidou E, Murray prevent secondary contamination; V. Surveillance into crowd control agents [let- medical staff should wear gloves and ter]. Lancet 1998;352:991-2. goggles when providing treatment. 2. Karalliedde L, Wheeler H, MacLehose R, Mur- ray V. Possible immediate and long-term health Washing with soap and water is not effects following exposure to recommended unless symptoms persist, agents [review]. Public Health 2000;114:238-48. 3. Gray PJ. Is CS spray dangerous? Formulation af- because the chemical agents can dis- fects toxicity [letter]. BMJ 2000;321:46. solve in water and exacerbate symp- 4. Fraunfelder FT. Is CS gas dangerous? Current toms or contaminate other surfaces. evidence suggests not but unanswered questions remain [editorial]. BMJ 2000;320:458-9. Hot water may cause any residual par- 5. Gray PJ, Murray V. Treating CS gas injuries to ticles to vaporize and give rise to sec- the eye. Exposure at close range is particularly ondary contamination.6 dangerous [letter]. BMJ 1995;311:871. 6. Blaho K, Stark MM. Is CS spray dangerous? CS Canapress/Ryan Remiorz Recommendations for treating eyes is a particulate spray, not a gas [letter]. BMJ Demonstrator kicks tear-gas canister contaminated with CS vary. Some sug- 2000;321:46. 7. Sommer S, Wilkinson SM. Exposure-pattern toward police during April clashes in gest blowing dry air with a fan over the dermatitis due to CS gas. Contact Dermatitis Quebec City eyes to vaporize the CS particles; the 1999;40:46-7.

1890 JAMC • 26 JUIN 2001; 164 (13)