Chemical Agents and Treaties

With the ever increasing threat of chemical warfare agents used by terrorists, law enforcement and public safety officials must be well informed. Here you will find information regarding various chemical warfare agents and policies governing them.

Chemical Agents

Detection of Chemical Weapons

Choice of correct protective equipment, and correct behavior, may be decisive for a unit's possibilities to operate in CW contaminated environment. Detection is vital in obtaining information on the risks. Detection implies that evidence is obtained on the types and quantities of CW agents in the area. The questions asked may be whether, for example, protective masks are required, whether body protection is necessary, if normal behavior should be modified in any special way, and whether equipment will require decontamination. Detection may be needed for several different purposes, e.g.,

Different types of detection require different types of equipment and methods. In some cases we must determine whether the gas concentration in the air is at a dangerous level. In other situations, investigations are made of whether soil or equipment is contaminated with liquid agent, i.e., is dangerous to handle.

Alarm

The simplest form of alarm is based on direct observations. A visible cloud drifts towards the observer, someone in the unit shows symptoms of poisoning, observations are made of dead animals, etc. Earlier and more reliable alarms require continuos and automatic monitoring of the gas concentration. For this purpose, instrumentation is today being developed and introduced.

An alarm detector must be capable of operating continuously for long periods. It should require no particular attention except for changing batteries, etc., and might be operated by personnel with short training periods. At a predetermined concentration of the relevant substance, the instrument emits signals either visually or acoustically. On the other hand, no direct reading of the concentration is required. An advantage is if different agents cause different alarms, e.g., different types of sound or different signal colors.

It must always be considered that other substances than CW agents may cause the alarm. It is important not only that these are as few as possible but also that they are known so that situations with false alarms can be avoided.

Detection paper placed onsite in advance is a simple manual method. It can be used as a warning for CW agents in the form of liquid fallout. In such cases, it is necessary to have continuos monitoring with special personnel.

All-clear

Wearing a protective mask and protective clothing implies a major physical and mental strain for personnel. Consequently, it is of major importance to sound the all-clear as soon as possible after a CW attack. Protective measures can be terminated when the concentration of CW agents in the air has fallen below the threshold limit.

A continuously operating all-clear system is again preferable. The need to sound the alarm may soon arise again if the conditions change. As regards the all-clear, an instrument which can be directly read-off is of great value. Such instruments, e.g., the British CAM (Chemical Agent Monitor, see illustration) show the air concentration for different types of substances. Changes can then be observed and a temporary fall in concentration can be utilized to decrease the level of protection, e.g., in order to eat. Correct utilization of an instrument with direct-reading facilities requires an operator and also someone with sufficient knowledge to reach correct decisions.

Provided there is access to other information, e.g., mapping of the ground contamination has been completed, manual methods using detection tubes or detection tickets may be sufficiently accurate when reaching decisions on sounding the all-clear.

Verification and Identification

In order to reach decisions on the level of protection required, it is necessary to know the type of agent present in the area and whether the concentration exceeds the threshold level. If alarms are sounded on the basis of vague detection reports (direct observations), the suspicions should be confirmed by verification.

Detection (enzyme) tickets and detection tubes are sufficient to demonstrate nerve agents and mustard agent under field conditions. A manual suction pump is used to draw air through the detection tube or against the ticket. Subsequently, the material is developed in order to see whether CW agents have affected the tube or ticket.

In order to reach tactical decisions, more detailed information on CW agents is necessary. This identification can be done to some extent by means of a combination of manual vapor detection (tickets and tubes) and detection paper. Information on an even higher reliability level will require analysis in a laboratory. Samples can then be taken in the field for subsequent analysis.

Mapping of Ground Contamination

In some cases, it is necessary to map which parts of an area are and which are not contaminated with CW agents in liquid form. This is essential if, for example, a convoy of vehicles has to pass through an area where CW agents have been used. Several methods are available. Traditionally, detection paper has been used. Detection papers prepared before an attack could give the information required. In such cases, this must have been made over the entire area in question and at several different places in the area. However, such information is probably not available or deficient.

Detection paper can be used in post factum detection. However, this method is not entirely reliable, particularly if a long period has passed between the contamination and detection occasions. Considerable quantities of CW agents may have been absorbed into the soil layer and still imply danger without giving any response on detection paper. Consequently, soil detection with paper should be complemented with some kind of vapor detection.

Another problem is that traditional methods of soil detection take a long time. The speed of a convoy of vehicles will decrease to a few km/h if detection must be conducted at the same time as the convoy makes progress. In this way, an aggressor achieves a considerable tactical advantage already with a low or moderate CW attack. By vapor detection with detectors or monitors, the speed of vehicles could be increased to about 30 km/h, provided that the instruments react sufficiently rapidly and are sufficiently sensitive.

Vapor detection is not a fully reliable method, and particularly not for CW agents with low volatility or at low temperatures. There is a risk that vehicles, ordnance, etc., may be contaminated after transport without this being detected using the actual transport.

Mapping of Decontamination Requirement

Mapping of the decontamination requirement involves approximately the same problems as mapping ground contamination although generally on a smaller scale. Detection with paper generally works well but is not sufficient in all situations. CW monitors are important in controlling the need for decontamination.

Persons suspected or known to be contaminated must be decontaminated immediately without previous time-consuming controls. This should also apply to personal equipment if it is reasonably easy to decontaminate. Checks of the decontamination requirement should be concentrated to heavier and more difficulty decontaminated equipment.

Developmental Trends

Development of detection methods today is mainly concentrated on instruments. New manual methods, e.g., for toxins, may be developed but the development mainly concerns instruments for detection and monitoring. In some cases, instruments capable of both tasks are being constructed.

Several lines of development are presently being followed as regards detection principles. The most common line of development is some form of ion mobility detector IMS (Ion Mobility Spectroscopy). The Chemical Agent Monitor (CAM) also belongs to this group, as well as detectors for warning such as the Finnish M86 and the more recent M90. Another principle used is flame photometry FPD (Flame Photometric Detector). A flame of hydrogen is allowed to burn the sample of air after which the color of the flame is investigated by a photometer. In this way, the presence of phosphorus and sulfur can be demonstrated. Examples of instruments using this principle are the French monitor AP2C and Israeli combined detector and monitor CHASE.

A third principle is to use enzymes, as in the manual methods for nerve agent detection. Detectors operating on this principle have been developed in the United Kingdom, in the Netherlands and the former Soviet Union, among others.

Methods for long-range monitoring using optical methods (IR) are being developed in France and the U.S.A.

A research sector attracting great interest is the use of biologically active molecules as sensors. These biosensors are believed to have extremely great potential and research is ongoing in several countries. The advantage of biosensors is that, at least in theory, they can be given the sensitivity and specificity desired. This is possible since the biosensor uses the same mechanisms that influence the human body when exposed to poisoning. A simple type of biosensor is the enzyme ticket.

A more general type of biosensor may also be useful in the early detection of potential threats. Instead of studying toxic substances, investigations can be made of which receptors in the body may be sensitive to, e.g., a toxin. These receptors could then be used in a biosensor.

Manual Detection Methods

Detection Paper
Detection paper is based on certain dyes being soluble in CW agents. Normally, two dyes and one pH indicator are used, which are mixed with cellulose fibers in a paper without special coloring (unbleached). When a drop of CW agent is absorbed by the paper, it dissolves one of the pigments. Mustard agent dissolves a red dye and nerve agent a yellow. In addition, VX causes the indicator to turn to blue which, together with the yellow, will become green/green-black.

Detection paper can thus be used to distinguish between three different types of CW agents. A disadvantage with the papers is that many other substances can also dissolve the pigments. Consequently, they should not be located in places where drops of, e.g., solvent, fat, oil or fuel can fall on them. Drops of water give no reaction.

On the basis of spot diameter and density on the detection paper, it is possible to obtain an opinion on the original size of the droplets and the degree of contamination. A droplet of 0.5 mm diameter gives a spot sized about 3 mm on the paper. A droplet/cm2 of this kind corresponds to a ground contamination of about 0.5 g/m2. The lower detection limit in favorable cases is 0.005 g/m2.

Detection Tubes
The detection tube for mustard agent is a glass tube containing silica gel impregnated with a substrate (DB-3). Detection air is sucked through the tube using a special pump. The reaction between the mustard agent and substrate (see below) is speeded up by heating the tube with, e.g., a cigarette lighter. A developer is then added, and the result can be read-off. If the silica gel in the tube turns blue, then the vapor in the sample contains mustard agent.

Detection Tickets
Detection tickets for nerve agents are used in a similar way. The ticket consists of two parts, one with enzyme-impregnated paper and the other with substrate-impregnated paper. When the package is broken and the enzyme paper wetted, the substrate part of the ticket is exposed to the test vapor by means of a pump.

Subsequently, the two parts are put together for two minutes. If the enzyme part of the ticket has turned a weak blue color, nerve agent is not present in the air. The detection limit is 0.02-0-05 mg/m3 depending on the number of strokes of the pump. The ticket can also be used without a pump (by waving it in the air) but this gives a slightly poorer sensitivity.

An example of the enzyme substrate reaction used in detection tickets for nerve agents can be seen below. Note that the blue change of color requires an active enzyme - some form of cholinesterase. In the presence of nerve agents, the enzyme is inhibited and no change of color occurs. Detection tickets of this kind cannot distinguish between the different nerve agents.

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An attack with CW agents achieves maximum effect when it is directed against an unprotected unit. However, by taking relatively simple protective measures, the injuries can be reduced considerably. In principle, it is possible to create practically complete CW protection but generally a slightly lower level is considered sufficient. If the protective level is sufficiently high, an aggressor will probably realize that a CW attack will not be cost effective.Effective CW protection requires the building-up of some kind of "barrier" around the soldier. However, the more the soldier is protected from the ambient conditions, the greater his mobility is restricted.

Personal Protection
During an attack with CW agents, the respiratory system must be protected against aerosols and gases in the air at the same time as the rest of the body must be protected against direct contact with CW agents in the form of liquid or solid particles. After the attack, the body must be protected against contact with CW agents on the ground and on equipment. In addition, the respiratory system must be protected against evaporating gas.

Protection for the Respiratory System
The level of protection provided by a protective mask or respirator against penetration of biological and chemical weapons through the respiratory system depends on:

In protection against chemical warfare agents the decontamination is an important unavoidable part. The aim of decontamination is to rapidly and effectively render harmless or remove poisonous substances both on personnel and equipment. High decontamination capacity is one of the factors which may reduce the effect of an attack with CW agents. In this way, it may act as a deterrent.

The need for decontamination should be minimized to the extent possible by contamination avoidance and early warning. Equipment can be covered, for example, or easily decontaminated equipment can be chosen by means of suitable design and resistant surface cover.

Decontamination is time consuming and requires resources. Nerve agents and substances causing injury to the skin and tissue are easily soluble in, and penetrate many different types of material, such as paint, plastics and rubber, all of which renders decontamination more difficult. If CW agents have penetrated sufficiently deep, then toxic gases can be released from the material for long periods. By adding substances which increase the viscosity of a CW agent, its persistence time and adhesive ability can be increased. These thickened agents will thus be more difficult to decontaminate with liquid decontaminants since they adhere to the material and are difficult to dissolve.

The need for decontamination can only be established by means of detection. If detection is not possible, then decontamination must be done solely on suspicion of contamination, e.g., if the unit has passed on the fringe of a contaminated area.

Decontaminants

All decontamination is based on one or more of the following principles:

• to destroy CW agents by chemically modifying them (destruction),
  
  
• to physically remove CW agents by absorption, washing or evaporation,
  
  
• to physically screen-off the CW agent so that it causes no damage.

Most CW agents can be destroyed by means of suitable chemicals. Some chemicals are effective against practically all types of substances. However, such chemicals may be unsuitable for use in certain conditions since they corrode, etch or erode the surface. Sodium hydroxide dissolved in organic solvent breaks down most substances but should not be used in decontaminating skin other than in extreme emergencies when alternative means are not available.

Decontaminants that have effect only against a certain group of substances can be an alternative in favor of a substance with general effect. The condition is that they will have a faster and better effect against the substance in question and/or a milder effect. Examples of such substances are chloramine solutions which are often used to decontaminate personnel. These have good effect against mustard agent and V-agents but are ineffective against nerve agents of G-type (sarin, soman, tabun). A water solution of soda rapidly renders nerve agents of G-type harmless but when used in connection with V-agents, it produces a final product which is almost as toxic as the original substance. This does not prevent V-agents being washed-off with a soda solution, provided a sufficient amount is used. However, the final product will always be poisonous.

The disadvantage of specifically-acting decontaminants is partly that it is necessary to know which CW agent has been used and partly that access to several different types of decontaminating substances is required.

Decontamination methods

CW agents can be washed and rinsed away, dried up, sucked up by absorbent substances, or removed by heat treatment. Water, with or without additives of detergents, soda, soap, etc., can be used, as well as organic solvents such as fuel, paraffin and carburetor spirit. Emulsified solvents in water can be used to dissolve and wash-off CW agents from equipment.

When decontaminating by washing, consideration must be taken to the poisonous substance remaining in the decontaminant unless the CW agent has first been destroyed. The penetration ability of a CW agent can be enhanced when mixed with solvent. Today, there is an international development towards chemically resistant paints and materials, which implies that water-based methods will become more effective. However, the need for penetrating decontamination methods will remain for many years.

When washing with water - particularly with hot water and detergent - the CW agent will often be decomposed to some extent through hydrolysis. Detergents containing perborates are particularly effective in destroying nerve agents. Without an addition of perborates in the detergent, the hydrolysis products of V-agents may still remain toxic unless the pH is sufficiently high. Mustard agent is encapsulated by the detergent and, consequently, the hydrolysis rate decreases in comparison with clean water. However, the low solubility of mustard agent makes it difficult to remove without the addition of detergent, but the water used will still contain undestroyed mustard agent.

Small areas of terrain, e.g., first-aid stations or gun sites, may be decontaminated by removal of the top-soil. Another alternative is to cover the soil with chlorinated lime powder (sludge), which is a decontaminant with general effect and which releases active chlorine. CW agents which have penetrated into the soil, from where they release toxic vapor, are screened-off since the gas and liquid is destroyed by the chlorinated lime.

The physical screening-off of CW agents by covering them can be done in the terrain by spreading a layer of soil or gravel over the contaminated area. The effect will be improved if bleaching powder is mixed into the covering material. Another example of covering is to use special plastic foil to cover contaminated areas inside vehicles. In this way, the personnel will be protected against transfer of liquid.

Individual Decontamination

The most important decontamination measure naturally concerns the individual. If it is suspected that skin has been exposed to liquid CW agents, then it must be decontaminated immediately (within a minute). All experience confirms that the most important factor is time; the means used in decontamination are of minor importance. Good results can be obtained with such widely differing means as talcum powder, flour, soap and water, or special decontaminants.

In complete decontamination, clothes and personal equipment must also be decontaminated. If clothes have been exposed to liquid contamination, then extreme care must be taken when undressing to avoid transferring CW agents to the skin. There may be particular problems when caring for injured since it may be necessary to remove their clothes by cutting them off. This must be done in such a way that the patient is not further injured through skin contact with CW agents. During subsequent treatment it is essential to ensure that the entire patient is decontaminated to avoid the risk of exposing the medical staff to the CW agents.

In most countries, a soldier's equipment includes means for individual decontamination, generally a mixture of chlorinated lime and magnesium oxide. This decontaminant works by absorbing liquid substances and also by releasing free chlorine which has a destructive effect on CW agents. The dry powder also has good effect on thickened agents since it bakes together the sticky substance which makes it easier to remove. Personal decontaminants containing chlorinated lime have, however, an irritating effect on the skin. Consequently, comprehensive use should be followed by a bath or shower within a few hours.

Liquid personal decontaminants are common in some countries. Sodium phenolate or sodium cresolate in alcohol solution are used for individual decontamination of nerve agents. Chloramines in alcohol solution, possibly with additional substances, are commonly used against, e.g., mustard agent. Instead of liquid individual decontaminants, it is possible to use an absorbent powder such as bentonite ("Fuller's Earth"). In the U.S.A. the wet method formerly used was replaced by a decontaminant powder based on a mixture of resins, which decompose CW agents, and an absorbent.

A factor common to all individual decontaminants is that they can effectively remove CW agents on the surface of the skin. However, they have only limited ability to remove CW agents which have become absorbed by the skin, even though very superficially. CW agents that have penetrated into the skin therefore function as a reservoir which may further contribute to the poisoning also after completed decontamination.

In some cases, a wet method may give a better result in decontaminating deeply penetrated agents than a dry method. Reports from France indicate that a solution of potassium permanganate gives effective destruction of CW agents on the surface of the skin and also a certain penetrating effect. There are also individual decontaminants which can simultaneously function as a protective cream for use as a prophylactic. Canada has developed a mixture of a reactive substance (potassium 2,3-butadion monoximate) in polyehylenglycol, which has both these properties. It can be applied to the skin either as a cream or with a moist tissue.

Decontamination of Equipment

Immediate decontamination of personal equipment and certain other kinds of smaller equipment is generally done with individual decontaminants. However, these substances are only capable of decontaminating liquid CW agents covering the surface. The decontamination is mainly done to prevent further penetration into the material and to decrease the risk when handling the equipment.

CW agents easily penetrate different materials and into crevasses and will thus be difficulty reached by methods only designed for superficial decontamination. When a CW agent has penetrated into the surface, it is necessary to use some kind of deep-penetrating method. If such a method cannot be used, then it must be realized that the equipment cannot be used for a long period. Depending on the type of CW agent used and prevailing weather, i.e., temperature, wind velocity and precipitation (water solubility), the "self-decontamination" may take many days or even weeks. The absorption into the surface and natural chemical degradation are important factors influencing the self-decontamination period.

Example of self-decontamination times for contamination on metal surfaces and on a typical (non-resistant) paint at +15C, 4 m/s and 2 mm large droplets.

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Influence of Weather, Terrain and Buildings