CS is a particulate spray, not a gas

EDITOR—The most recent edition of the British National Formulary reviews the emergency treatment of patients exposed to 2-chlorobenzylidene malononitrile (CS) spray. 1 It is important to note that as used in the United Kingdom CS is not a gas but a particulate spray formulated for use against a violent individual. Law enforcement agencies have expressed concern about the use of CS spray. 2 3 The Department of Health has issued a comprehensive report on CS spray, concluding that there are no health concerns about the effects of CS when used appropriately.4

In the context of law enforcement, using chemical restraints is safer than hands-on contact or using other weapons that have a higher probability of causing death.5 CS has been used in the United States and has a long history of safe and effective use. No consistent adverse effects from acute exposure have been documented, nor has excessive or unfounded use been a problem. In Memphis, Tennessee, the introduction of chemical restraints in the police department dramatically decreased the number of injuries to police officers and to prisoners as well as decreasing the number of complaints of excessive force made against officers.5 In Tennessee all officers undergo training in which they are exposed to both CS and oleum capsicum, and no significant injuries from exposure have been reported.

The most important aspect of managing a patient who has been exposed to CS is to practise good hygiene by removing any contaminated clothing and to ensure that the individual is exposed to air and is not placed in a confined space before decontamination. Special attention should be paid to limiting secondary exposure by using protective clothing such as gloves and by putting contaminated clothing into bags. In most cases this is all the treatment that is needed. Left untreated, most symptoms will resolve within minutes of exposure.

Washing with soap and water is not recommended unless symptoms persist. The particulate form of CS can dissolve in the irrigant and exacerbate irritation or contaminate other surfaces, such as the eyes. In the rare instances when irrigation is required, normal saline, not water, is the best choice. If symptoms persist then evaluation by a physician is warranted. The most common persistent complaint is ocular irritation, and this is usually the result of a particle of CS becoming embedded in the ocular surface. In this instance, copious irrigation with saline and a thorough slit lamp examination should be carried out.

Formulation affects toxicity

EDITOR—Fraunfelder's editorial contains several misconceptions stemming from the question posed in the title of whether CS gas (2-chlorobenzylidene malononitrile) is dangerous.1 At room temperature, CS is a solid and cannot be described as a gas. When used for riot control purposes, it is dispersed as a microparticulate cloud produced by a pyrotechnic device. CS has a very low aqueous solubility and is in fact hydrolysed to inactive products. Thus, to deploy CS as a spray, a non-aqueous solvent needs to be used, which in the sprays used by British police is methyl isobutyl ketone.

Methyl isobutyl ketone is an industrial degreasing agent that will remove lipid from the skin, causing reddening, scaling, blistering, and peeling as well as irritating the eyes and respiratory tract. In the chemical industry the use of skin and eye protection is advised when handling the substance,2 yet, paradoxically, the British police are trained to spray this chemical directly into a person's face. Their delivery device is not an aerosol akin to that which dispenses hair lacquer but should be described as a “squirt can” from which a stream of liquid is released similar to that which dispenses windscreen de-icer.

It is important to consider the physicochemical properties of CS when treating patients contaminated with it. Patients should be advised to stay in the open air, ideally facing into the wind, and any contaminated clothing should be removed. To treat ocular exposure, irrigation and removal of any solid fragments is to be recommended because CS is hydrolysed to inactive products and “blow drying” will not cause CS to evaporate and may contaminate the medical facility by blowing residual CS away from clothing.

Although much research confirms the safety of CS when used at low concentrations (1 part per 100 000 000) as a microparticulate cloud for riot control purposes,3 experimental studies have found that ocular damage occurs after the application of high concentrations of CS to the eye, especially when applied in solution.4 There have also been case reports of significant ophthalmological sequelae.5 I have seen many cases in patients and police constables occurring after the use of CS incapacitant, some of these are still under judicial consideration for the award of damages. CS thus has health and safety implications for those who use it at work.

The key issue with regard to the safety of CS is not CS toxicity itself but that of its formulation.

Hazards are being hidden

EDITOR—It might have been more appropriate for Fraunfelder to ask not if CS (2-chlorobenzylidene malononitrile) is dangerous but if, as the British government has consistently maintained, it is genuinely safe.1 In assessing the hazards of CS aerosols, the Himsworth committee recommended that the dose-effectiveness relation of an agent used for riot control should be akin to that of a drug and be tested accordingly.2 Questions to ministers in both houses of parliament referred specifically to CS spray, a formulation introducing a pharmacological dimension wholly different from CS. Replies disingenuously claimed that CS “had been tested to a level similar to that required for a new pharmaceutical drug.”3 This is misleading and irrelevant.

The recent report from the Department of Health is disturbingly flawed.4 Firstly, despite citing the Himsworth report, the drug analogy was completely ignored. Secondly, by emphasising the lack of data on the effects of the formulated product, the report deprived its conclusions of authority. Thirdly, the report confined itself almost entirely to separate considerations of CS and its spray solvent, largely discounting the only description of the effects of the spray in humans.5 Erythematous dermatitis and extensive blistering have been described in humans, and some patients developed keratitis.5 Fourthly, no field tests or follow up studies were conducted. In the sharpest contrast, Himsworth et al voluntarily exposed themselves to CS aerosol from a munition, providing a vivid first hand account of its actions.2 There is no description of the excruciatingly painful effects of the spray on eyes and face. Instead the report states that “systematic studies in volunteers to investigate the toxicity of CS spray may present insurmountable difficulties.”4

However, allergic contact dermatitis from repeated exposure to CS was authenticated.4 Sufficient references were provided to indicate that allergic dermatitis arising from multiple exposures, an experience with which many police are familiar, will pose a problem, at least for some among junior officers. Ironically, CS spray, ostensibly introduced with the intention of protecting officers, may be damaging to health.

When politicians and the public discover that there has been absolutely no testing of CS spray in the sense intended by Himsworth and realise the extent to which they have been misled by the Home Office, the political repercussions, as well as costs and damages arising from litigation, are likely to prove substantial and hugely embarrassing.