The domestic approach to potential terrorist attacks using chemical, biological, or toxinweapons attempts to balance a "post-event" consequence management approach with a "pre-event,"preventative approach. Legislation and plans have been developed to address the casualties fromchemical, biological, or toxin weapons, generally focused on the physical consequences of suchweapon use and methods to provide prompt consequence management. Further efforts regardingpublic outreach, enhancing treatment and prophylaxis through federal initiatives, or additionalregulation of materials used in developing chemical, biological, and toxin weapons are areaspolicymakers may revisit as preventative approaches to reduce the enhanced terror aspect of theseweapons This report provides a general overview of chemical, biological, and toxin weapons and their treatment; a summary of why some of these weapons may be more attractive to terrorist groups thanconventional weapons; select aspects of the current response against chemical, biological and toxinterrorism; and potential options towards lessening these weapons' impact. The widespread public unease following the anthrax mailings and the continued concernregarding possible terrorist use of weapons of mass destruction - nuclear, chemical, biological, orradiological - have highlighted the potential these weapons may have to a terrorist group. (1) Thisreport focuses on chemical, biological, and toxin weapons, whose impact and nature differ from eachother and from nuclear or radiological weapons. Chemical weapons are chemical compounds that have a strong, deleterious effect on the human body, even when encountered in small doses. The different types of chemical weapons includevesicants, which blister and burn on contact; choking agents, which cause lung damage; and nerveagents, which interfere with the nervous system and may lead to death. The effects from chemicalweapons may occur very quickly after exposure, on the order of minutes to hours. (2) Biological weapons are pathogens that cause disease and illness in infected humans. Because the pathogens multiply within the victim, a small initial amount of pathogen is sufficient to causeinfection. As a consequence, biological weapons require much less material than chemical weaponsto produce equivalent casualties and generally take longer to produce effects. Biological weaponsinclude diseases that are primarily incapacitating, such as Q fever, as well as those that are lethal,such as smallpox. Some biological weapons are contagious pathogens, such as smallpox, and havethe potential to spread the effects of an attack by traveling from victim to victim. The symptomsfrom a biological weapon attack would require some time to develop, so a covert biological attackmight not be recognized for several days. (3) Toxin weapons are primarily illness-inducing chemicals formed from living creatures, such as bacteria, fungi, plants, and animals. Toxins range in effect from disabling to acutely toxic. The mostdeadly compound currently known, botulinum toxin, is a bacterial toxin. Toxins are more potentthan chemical weapons, requiring less material to produce equivalent casualties, but they are notself-reproducing, so more material is required than for a biological weapon. Symptoms from toxinexposure typically occur on a timescale intermediate between chemical and biological weapons,generally appearing over the course of several hours. (4) The difficulty of obtaining or developing chemical, biological, or toxin weapons has made their use very rare, but these weapons have been used for terror purposes. Sarin, a chemical nerve agent,was used in the Tokyo subway system in 1995 by the Aum Shinrikyo cult. (5) Anthrax bacteria, abiological agent, was used in 2001, infecting individuals in Connecticut, New York, Florida, and theDistrict of Columbia. Also, salmonella bacteria was used by the Rajneeshee cult in 1984 in anattempt to influence local election turnout. Ricin, a toxin, was mailed to the White House in 2003and Congress in 2004. Additionally, there have been arrests and news reports of individuals and terrorist organizations that have tried to develop and use chemical and toxin weapons. Videotapes acquired and broadcastby CNN have shown the effects of a chemical agent on test animals. (6) In 2003, Britishlaw-enforcement officials arrested several people accused of manufacturing ricin in a Londonapartment. (7) Previously, it was thought that the difficulties of developing, weaponizing, and disseminating chemical, biological, and toxin weapons provided high barriers to their use by non-state actors. (8) Advances in molecular biology, chemistry, and engineering have increased the ease by whichbiological and chemical compounds can be manufactured. Purchasable civilian technologies maybe applicable to manufacture of chemical, biological, and toxin weapons. (9) The Defense ThreatReduction Agency was able to assemble the requisite equipment from civilian sources. UnderProject BACUS, a biological agent production facility was successfully built in Nevada fromdual-use technology without drawing regulatory attention. (10) Some experts maintain that thetechnological barriers to chemical, biological, and toxin use have significantly decreased. Chemical, biological, and toxin weapons also differ in their medical treatment and theavailability of effective prophylaxis. (11) Chemicalweapons, with their quick-acting effects, must betreated as promptly as possible. Because of the large range of potential effects caused by chemicalweapons, there is no universal treatment for chemical weapon exposure. (12) Exposure to nerve agentscan be directly treated with medication to prevent or reduce symptoms. Exposure to vesicants, suchas mustard gas, is generally untreatable; most people exposed will exhibit the agent's effects. Theeffects from vesicant exposure, primarily blisters and lesions, can be treated. In addition, injury fromexposure to choking agents, such as chlorine, can be ameliorated by prompt medical treatment tolimit permanent lung damage. Many biological agents either respond to medical treatment or have effective prophylaxis. Single or combination antibiotic regimens, if employed early in the course of the disease, areeffective against many bacteria that might be used as biological weapons. Such timely treatmentmay be difficult if recognition of a bioterror event is delayed. Some viruses targeted as biologicalweapons have effective prophylaxis in the form of vaccines, while others reportedly respond toantiviral drugs. (13) However, some potentialbiological weapons lack prophylaxis, treatment, or cure. Additionally, biological weapons can be engineered, with some effort, in a laboratory to be resistantto specific countermeasures. Treatment of injuries sustained from toxin weapons may be more complicated. Anti-toxins and toxoid vaccines can be developed against toxin weapons, but the process for doing so is involvedand time-consuming. Consequently, stores of these medicines are limited in scope, (14) and a largenumber of toxin weapon casualties could exhaust local supplies. Some toxins, such as botulinumtoxin, cause death by paralyzing the muscles used for breathing. These toxins can be treated withsupportive care, through artificial ventilation and other means, until the patients recover. For bioterror events, it is difficult to project the likely treatment success rate. Treatment of chemical, biological, and toxin weapons relies on providing medication within a relatively narrowtime window. If medication is not provided fairly quickly after exposure or the development ofsymptoms, depending on the weapon, full recovery is unlikely. By their nature, terrorist events are unexpected, shocking, and often perceived as random, andthey evoke a sense of fear and uncertainty. Chemical, biological, and toxin weapons use maycontribute additional considerations. In part, this is because chemical, biological, and toxin weaponshave the potential to cause mass casualties. Effectively disseminated, a single release of a chemicalor biological weapon could cause tens of thousands of casualties. (15) This ability to inflict greatnumbers of casualties may cause terrorists to view chemical or biological weapons as a viable meansfor promoting an agenda of terror and destruction. The impact of these weapons may be magnifiedby other factors. The use of chemical, biological, or toxin weapons in terror attacks could complicate emergency response due to the need to establish special care facilities for the victims, such as decontaminationareas, and the need to protect first responders from the weapon's effects. If first responders becamevictims through inadequate personal protective equipment or contamination of emergency vehicles,increased casualties and greater social disruption could result. Furthermore, chemical, biological, and toxin weapons may produce a wide array of effects. Terrorists may believe they can select chemical, biological, or toxin weapons to produce specificresults for certain situations. They may believe that these weapons increase their operationalflexibility. (16) Since for some chemical, biological,and toxin weapons there exists a delay beforesymptoms develop, terrorists may feel that their use will increase the chances of successfullyavoiding arrest. The variety of potential effects and timing can complicate medical treatment andpreparedness, as it might not be readily apparent what chemical or pathogen has caused thesymptoms, nor what antidote will prove most effective. (17) The use of chemical or toxin weapons could generate a disproportionate public response because of a broad public perception that their use is akin to poisoning. According to experts, therehas long been fear of and antipathy towards the use of poison. It is especially frightening to thevictim, as the symptoms may seem to appear from nowhere. Poisons lacking an antidote may raiseconcerns further, as the victim perceives that there is no recourse or cure available. The dreadgenerated from the inability to control the situation, and oftentimes one's own bodily safety, iscommon to victims of chemical weapons, and multiplies anxieties related to these weapons' use. (18) Biological weapon use may evoke deep-seated concerns regarding epidemic disease and sickness. (19) Plagues have historical and religiousassociations, (20) and more recent epidemics havelefttheir mark on society. (21) Furthermore, victims ofdiseases that manifest symptoms externally, suchas smallpox, may enhance concerns with respect to contagion.