Effective emergency response planning under the CSEPP requires an adequate understanding of the chemical agents involved and the way they are stockpiled. This section describes aspects of the agents and stockpiles pertinent to emergency planning. The chemical agents are described in terms of characteristics that affect the form in which they could be released and the ways in which they would present an exposure hazard to humans. In addition, this section discusses the toxicity of the agents and the public health and environmental impacts that might occur if they were released. The stockpile is described in terms of the relative amount of agent stored at each location, the various munitions and containers in which the agents are stored, and the general physical characteristics of the storage areas.

The agents of primary concern in this guidance are the nerve agents GB, and VX and the blister agents H, HT and HD. (Nerve agent GA and blister agent Lewisite (L) are also stored in minor quantities at one stockpile location. Agents GA and L present a small planning concern. (See Table 1.) The chemical and physical properties of these agents have a direct bearing on emergency planning and response. The chemical and physical properties determine the agents' volatility, behavior in fires, and persistence in the environment. Agent toxicity determines the impact on human, animal, or plant life. Appendix B of the FPEIS describes these properties in detail. They are discussed here only in relation to emergency response planning.

All of the agents are liquids at normal indoor temperatures, although most sulfur mustards (H and HD) freeze at ambient temperatures below 13 to 15 degrees C (55 to 59 degrees F). The sulfur mustard agent blend, HT, freezes at ambient temperatures below 0 to 1.3 degrees C (32-34.3 degrees F). The mustard agents have relatively high boiling points (215 to 217 degrees C or 419 to 423 degrees F for agents H and HD; the boiling point for agent HT is greater than 228 degrees C, or 442 degrees F). However, the mustard agents have significant vapor pressures at ambient temperatures. Therefore, mustards pose an inhalation hazard at higher ambient temperatures.

In pure form, the nerve agents (GA, GB, and VX) are usually odorless, colorless (agent VX may be pale amber), and tasteless. GA and GB are nonpersistent nerve agents which primarily present a vapor hazard. The vapors from these agents would present the primary casualty producer since they can be carried downwind quickly. Under most release and meteorological conditions GA and GB produce the greatest downwind hazard distance when compared to other agents in the stockpile. Thermal decomposition of GA and GB begins at approximately 130 degrees C (266 degrees F), and they completely decompose in 2.5 hours at 150 degrees C (302 degrees F).

Nerve agent VX is a persistent agent which presents both a vapor and a percutaneous threat. VX is not very volatile, so it presents much less vapor hazard than GA and GB; however, it is 100 times more toxic by the percutaneous route. Therefore, if VX is aerosolized due to an explosive release, it presents a percutaneous downwind hazard. Thermal decomposition rates of VX are 1.5 hours at 200 degrees C (392 degrees F), 4 minutes at 250 degrees C (482 degrees F), and 36 seconds at 295 degrees C (563 degrees F). In practical terms, a toxic dose of VX is more likely to result from skin rather than respiratory exposure; however, all nerve agents are sufficiently volatile to pose an inhalation hazard. At agent concentrations of 30 mg/m3 or greater, median lethal inhalation doses can be attained in a few minutes.

In the unlikely event of fires or explosions, on-post personnel and the off-post general public could be exposed to agent combustion products as well as uncombusted agents. Nerve agents are destroyed at the high temperature of a fuel fire and, in addition, VX is flammable. Data indicate that at flame temperatures above 400 degrees C (752 degrees F), both VX and G agents would be decomposed within two to three minutes. Nevertheless, fire involving vesicant and nerve agents could produce toxic combustion products.

The agents GA, GB, and VX are rapidly acting, lethal nerve agents. They directly affect the nervous system and are toxic as liquids and vapors. They are organophosphorus esters that inhibit acetylcholinesterase, an enzyme that prevents the accumulation of the neurotransmitter acetylcholine at the nerve synapses. When too much acetylcholine is present, over-stimulation of the nerve ending occurs. The result is over-reaction of muscles, glands and the central nervous system.

The severity of symptoms of acute exposure to the nerve agents depends on the quantity and dose rate of the exposure. Signs and symptoms may include tightness of the chest, pinpointing of the pupils of the eyes (miosis), breathing difficulties, drooling and excessive sweating, nausea, vomiting, cramps, twitching and staggering, headaches and convulsion, followed by cessation of breathing and death. At low-dose (and non-lethal) exposures, signs and symptoms may not develop for hours post-exposure.

The vesicant agents (H, HD, and HT) injure the eyes, damage the lungs and severely blister the skin upon exposure. The vesicants can often react with tissue constituents, and there is significant evidence that exposure to sufficiently high doses may increase the risk of developing cancer. The vesicant agents are potent in minute quantities and produce delayed effects as late as 24 hours after contact.

If chemical agents are released, severe human health effects could result. The magnitude of the impact would depend on a number of variables: the amount and type of agent released; the method of release (e.g., spill, explosion, etc.); meteorological conditions; the number of unprotected people potentially exposed to the agent(s); distance from the chemical event to the unprotected individuals; age, gender, and health of exposed populations; route and duration of exposure; and timeliness of decontamination and medical treatment.

The Army's Gaussian-plume dispersion model, D2PC, is used to predict the size and location of areas affected by releases of chemical agents. The model predicts areas affected by time-weighted average concentrations likely to produce fatalities and lesser health effects. The D2PC code incorporates chemical agent source-term information as well as characteristics of the various chemical agents, based on field testing with the actual munitions and simulants of the chemical agents.

The resulting dose-rate values are based on the assumption that the majority of the dose is absorbed by inhalation and that the individuals exposed are wearing clothing. In the case of VX, the lethality estimates for human exposure through the skin change dramatically as a function of the amount of clothing worn and the wind speed. Although the majority of the potentially exposed population would be expected to be clothed, many individuals would be expected to have portions of their bodies exposed. Thus adjustments to the toxicity levels should be made in some modeling applications for civilian populations. Certain members of the population may be more susceptible to agent exposure, e.g., infants, the elderly, and individuals debilitated by chronic disease. The FPEIS discusses this in some detail and provides civilian application criteria. (See FPEIS, Appendix B, "Toxicity of Warfare Agents and Their Breakdown Products," pp. B-112 ff.) As explained in Sect. 5, the emergency planning zones (EPZs) are based partially on these considerations.

In addition to the concern over acute and chronic human health effects, emergency response planning must consider impacts on the environment, drinking water sources, food supplies, and other natural resources. Additionally, environmental contamination would affect the time period required before return of evacuated personnel could begin after termination of the immediate airborne health hazard.

Data on persistence of chemical agents indicate that attention should be given to potential effects on food supplies, livestock and croplands. Because it is unlikely that such contamination would occur, this is a secondary planning concern. Contamination of surface water bodies used as public water supplies would be of concern only if a spill of liquid agent occurred directly into the water body. Groundwater supplies could be affected if there was a direct spill or leak into a well or spring. Such releases are extremely unlikely.

Persistent chemical agent (e.g., sulfur mustard or nerve agent VX) contamination of land surfaces poses a threat of potential contamination to the surface of exposed food items (e.g., fruit, leafy vegetables, etc.) in areas where high-level plume deposition could occur. Toxic effects to grazing animals can be expected from ingestion of forage, or dermal contact with objects contaminated by the persistent chemical agents. The volatile G-agents are not considered a source of significant surface contamination.

Because of the limited data on persistence and environmental distribution, it may be difficult to predict the amount of time required before the public can return to evacuated areas. Monitoring and sampling of the affected areas will be necessary to support decisions on return.

Chemical agents, predominantly GB, VX, H, HD, and HT, are stored at eight installations: Tooele Army Depot, Utah (42.3% of the total stockpile); Pine Bluff Arsenal, Arkansas (12.0%); Umatilla Depot Activity, Oregon (11.6%); Pueblo Depot Activity, Colorado (9.9%); Anniston Army Depot, Alabama (7.1%); Aberdeen Proving Ground, Maryland (5.0%); Newport Army Ammunition Plant, Indiana (3.9%); and Blue Grass Army Depot, Kentucky (1.6%). The remaining 6.6% of the stockpile is located outside of the continental United States at Johnston Island in the Pacific Ocean. All percentage figures are based on weight.

The chemical agents are stored in three basic configurations: (1) projectiles, cartridges, mines, and rockets containing propellant and/or explosive components; (2) aircraft-delivered munitions that do not contain explosive components; and (3) steel one-ton containers (see Figure 2). Most of the stockpile (61%) is in the latter last form. All of the agents are at least 20 years old; some are more than 40 years old.

Each stockpile is stored in a chemical exclusion area at each installation. Most of the stockpile is kept on pallets, in boxes, in cans, and is stored in earthen-covered bunkers ("igloos") specifically designed to contain the force of an explosion (see Figure 3). The igloos have lightning protection systems and steel doors and are equipped with multiple locking systems. Usually, only a single, agent-specific munition type is stored in an individual igloo (e.g., VX rockets in one igloo, VX land mines in a separate igloo, etc.).

Fig. 3 Chemical agent storage igloo

Some one-ton containers of mustard and VX agents are stored in warehouses or outside; when outside they are secured with chains. In either case, they are stored within an exclusion area. Extensive security precautions protect exclusion areas. Access is strictly controlled by security forces, intrusion detection devices, barricades, and perimeter lighting.