Medical Aspects of Chemical Warfare (2008) - The Black Vault

Riot Control Agentsnumerous factors, including the type and age of plantused for isolation and the method of extraction. Manyof the physiological responses induced by OC are dueto a family of compounds known as capsaicinoids. OCis 0.1% to 1.0% capsaicinoids by dry mass. The maincapsaicinoid of interest as an irritant and RCA is capsaicin(trans-8-methyl-N-vanillyl-6-noneamide). Thecapsaicinoids content of OC is approximately 70% capsaicin,20% dihydrocapsaicin, 7% norhydrocapsaicin,1% homocapsaicin, and 1% homodihydrocapsaicin.Historically, capsicum was used as a weapon by theancient Chinese and Japanese police. In 1492 nativeMexicans burned pepper in oil to create an irritatingand suffocating smoke. 91 OC in small doses is used medicinallyas a topical analgesic or counter-irritant. Capsaicinspray is also used in the pharmaceutical industryto induce cough for testing antitussive candidates. 92Recently PAVA (nonivamide), a structural analog ofcapsaicin, was synthesized. PAVA, which can be usedinstead of naturally derived OC sprays, is believedto have similar but safer effects and more consistentingredients than the natural form of OC. 4,93Physical Characteristics and DeploymentCapsaicin (Chemical Abstracts Service [CAS] registrynumber 404-86-4) has a molecular weight of 305.41and a molecular formula of C 18H 27NO 3(See Figure 13-6;Table 13-1). An odorless crystalline to waxy compound,capsaicin has limited solubility in water. OC is a derivativeof hot cayenne peppers. PAVA (CAS 2444-46-4) hasa molecular formula of C 17H 27NO 3(Figure 13-7) and amolecular weight of 293.4. 93,94Because of its highly effective irritant properties,OC has found widespread use in various military,government, and civilian agencies for riot control andindividual protection. OC is also available to the generalpublic for personal protection. US forces deployedto Somalia carried nonlethal packages that includedOC. Military police from several US Army divisions aswell as several Marine Corps units, who have used OCin the past, are currently investigating its capabilitiesand supporting its use. 10,95 Numerous formulations ofOC have been developed and marketed (commonlyreferred to as pepper spray, pepper mace, and peppergas), but there appears to be no standardization.Major factors separating one OC spray from anotherare the delivery device, carrier, and propellantsystem. 95 Currently, the most popular carrier is isopropylalcohol. Additional carriers have included Freon,Dymel-22 (both made by DuPont, Wilmington, Del),and methylene chloride. However, with the exceptionof isopropyl alcohol, most OC carriers and propellantsare currently banned or have use restricted by the 1987Montreal Protocol, which attempts to regulate the useof chemicals with the potential to adversely affect theozone layer.The use of isopropyl alcohol as a carrier complicatesthe toxic effect of OC in two ways. First, isopropyl alcoholand other volatile carriers readily evaporate inthe environment, and evaporation rates from OC fogand OC mist are greater than from OC streams, makingit challenging to calculate the actual concentration ofOC (ie, dose) on the target tissue. Second, isopropylalcohol has physiological effects (as do the other over100 constituents of oleoresin), causing a mild transitoryinjury (grade 4 on a scale of 10) when applied torabbit eyes. 96 Additionally, the interaction of the othercapsaicinoids in the oleoresin with capsaicin have notbeen well defined.A variety of dissemination devices for OC exist,including many commercial preparations, and themethod of choice depends largely on the number ofexpected subjects. These devices range from smallitems such as fake pens and pressurized cans, used toincapacitate subjects at close range, to grenades andcartridges for shotgun-mounted launchers, used tocontrol groups of individuals from a distance. Somedissemination devices release OC as a fine mist orfog; others spray a stream of OC towards the subject.More recently OC has been dispensed in a “pepperball”—a gel ball (similar to a recreational paint gunball), fired from a high pressure air gun, that hits theindividual and breaks on contact, releasing aerosolizeddry OC. 97OOOOHHONHCNHOCH 3Fig. 13-6. Chemical structure of capsaicin.Fig. 13-7. Chemical structure of pelargonyl vanillylamide.453