chemical agents (1)

CHEMICAL ENGINEERING DEPARTMENT

CHEMICAL AGENTS AND

BIOLOGICAL AGENTS

1WONDINET M. CHE. ENGG 2/7/2011

CHEMICAL AGENTS

2/7/2011 WONDINET M. CHE. ENGG 2

Introduction to Chemical AgentsChemical agent • a chemical substance which is intended for use in

military operations to kill, seriously injure or incapacitate people because of it’s physiologic effects.

• It is a warfare with the use of toxic chemicals to harass, incapacitate, or kill men and cattle or destroy vegetation.

• the use of synthetically produced chemical compounds to kill or injure humans, animals, and plants

• It owes its destructive power entirely to toxicity of one or more of its constituent chemical rather than the energy of chemical interaction between them.


Dissemination

• A chemical agent may be disseminated in one or more of the following forms:1. Liquid droplets or spray like rain

2. Liquid aerosols, like fine mist, small enough to be inhaled

3. Solid aerosols, like smoke

4. Vapor or true gas


Routs of entry

• Inhalation

• Ingestion

• Injection

• Absorption on skin


Classification of chemical agents

1. Based on duration of effectiveness

2. Based on tactical use

3. Based on specific use


Based on duration of effectiveness• Chemicals may be either persistent or non-persistent.1.Persistent chemicals• Persistent chemicals do not evaporate or break down

quickly, and may take days to weeks to become harmless.

• The rate of their evaporation or breakdown depends on environmental conditions including temperature, wind, humidity, and surface type.

• Release of persistent chemicals may require isolation of the contaminated area until decontamination is complete, and may thereby cause a longer-term disruption. 7WONDINET M. CHE. ENGG 2/7/2011

Based on duration……Non-persistent In contrast to persistent chemicals, non-persistent

chemicals dissipate quickly, and thus represent only a short-term hazard after they are completely released.

Non-persistent chemicals are typically gases and liquids that evaporate quickly.

Most of the common industrial chemicals carried in bulk in the transportation system are non-persistent.

Examples of these include chlorine and ammonia.8WONDINET M. CHE. ENGG 2/7/2011

Based on tactical use

1. Lethal agents: also known as killer agents.

These are delivered with the primary object of killing the maximum number of men

Example: nerve agents GB and VX

2. Incapacitating agents: these are selected to avoid causing death, but to make men temporarily unable to perform their duties.


Based on specific use

• Five of the more common chemical warfare categories are:

Nerve agentsBlister agentsChoking agentsBlood agentsRiot-control agents


Nerve Agents Vary in persistence from a few hours to a few weeks.

They can quickly disrupt the nervous system causing convulsions, and if the dose is high enough, paralysis and death.

Reactions normally occur minutes after inhalation or several hours after skin contact.

Nerve agents are hundreds to thousands times more lethal than blister, choking or blood agents.

Most useful to terrorists because only a minute quantity is necessary to cause a substantial amount of casualties.

In their most effective form, most nerve agents are more difficult to obtain.


Nerve Agents• Nerve agents severely inhibit neuromuscular function of the

body.• Muscular function is essentially a chemical process, which occurs

at the neuromuscular junctions.• Electrical impulses from the brain releases acetylcholine at those

points• Acetylcholine causes the muscles to contract.• The contraction to be relaxed subsequently.• Acetyl choline is destroyed by the enzyme acetyl cholinesterase

by hydrolysis.• Nerve agents deplete the acetyl cholinesterase in the blood.• Thus the control over the affected nervous system is lost.• Further acetyl choline builds up in the body which is a strong

poison.• The effect of one exposure add up to the effects of subsequent

exposures making them cumulative.12WONDINET M. CHE. ENGG 2/7/2011

Nerve Agents• Nerve gases are classified as ‘G’ agents or ‘V’ agents. They are

organophosphorus compounds.• Most commonly used ‘G’ agents are SOMAN(C7H16P2FO),

TABUN(C5H11N2PO2), and SARIN(C4H10PFO2)• Their odor are fruity like and are in vapor, liquid or aerosol form.• They effect 10 munities after inhalation and 30 minutes after

skin attack.• They cause tightness of chest, headache, diminished vision,

weakness, nausea, muscular twitching, collapse and breathing stops.

• ‘V’ agents are absorbed in the skin faster than and are more reliable than ‘G’ agents . They are probably dialkyl amino ethyl alkyl phosphonethiolates.

• VX and SARIN, the most toxic of the nerve agents, can be synthesized by a moderately competent organic chemist.


Nerve Agents

•• The GThe G--series:series:TabanTaban (GA)(GA)

Sarin (GB)Sarin (GB)

SomanSoman (GD)(GD)

•• The VThe V--series:series:VXVX

At room temp amber to colorless liquid stateWeak fruity (G) to fishy (VX) smell G-series more volatile (SARIN) than V-series V-series more toxic


Nerve Agents, V-series VX: A clear, colorless liquid – technically named

methylphosphonothioic acid and described as the most deadly nerve agent ever created. Absorption: Through eyes, lungs and skin Effects: Like other nerve agents, VX attacks the

nervous system – severe doses can cause death within 15 minutes of exposure. Lethal dose: Fraction of a drop Symptoms: Small doses trigger nasal discharge,

chest tightness, wheezing and headaches– severe doses lead to convulsions, confusion and

respiratory failure. Protection: Immediate injection of atropine


Nerve Agents, G-seriesSarin: A colorless liquid several times more deadly

than cyanide. Sarin is related to a group of pesticides and was initially developed in Germany in the 1930s.

• Effects: Sarin attacks the nervous system when inhaled or absorbed through the skin. Inhalation can cause death within 1-10 minutes of exposure.

• Lethal dose: 0.5 milligrams • Symptoms: Pupils shrink to pinpoints and

sweating and twitching precede symptoms similar to those for VX exposure.

• Protection: Injection of antidote immediately after contact.


Nerve Agents, G-series

Tabun: Also known as GB. Tabun was discovered in Germany by Dr Gerhard Schrader, who also first developed Sarin. Effects: If inhaled or absorbed through the eyes or

skin, Tabun can kill in as little as one or two minutes. Symptoms: Similar to VX and Sarin. Protection: Injection of antidote immediately after

contact.


2. Blister Agents(Vesicants)

A group of chemical agents that burn and blister skin and destroy eyes and tissue with which they come into contact.

They are often persistent. When touched, these agents destroy the skin. Skin irritation is felt within minutes or hours depending on

the agent. Blister agents are usually oily droplets that may penetrate

ordinary clothing. With eye contact, they can cause blindness. Inhalation can result in fatal respiratory damage. Mustard gas (which is truly a liquid), is common in chemical

warfare, and is an example of a blister agent.18WONDINET M. CHE. ENGG 2/7/2011

Blister Agents(Vesicants

• Mustard gases Sulfur Mustard

• Lewisite

• Halogenated oximes


Mustard GasMustard gas: A group of sulphur-, nitrogen-, and oxygen-

based vesicant compounds with similar chemical and biological effects

– Mustard is liquid at room temperature, but is more commonly used in its gas form - which has a strong smell likened to horseradish or garlic.

– Absorption: Contact with skin or inhalation– Effects: Mustard gas is a blistering agent, burning eyes

and skin exposed to it and lungs, mouth and throat if it is inhaled. It is not normally lethal, but can cause cancer and serious disfigurement.

– Symptoms: Conjunctivitis, skin burns, throat pain, cough and susceptibility to infection and pneumonia. Symptoms are not usually noticed until 1 – 6 hours after exposure.

– Protection: Protective clothing and early decontamination, followed by antibiotics.


Lewisite

• Description– Pure Lewisite is an oily, colourless liquid, while

impure Lewisite is amber to black with odour of geraniums.

• Routes of exposure – Inhalation

– Skin/Eye contact

– Ingestion


3. Choking Agents:• are usually not persistent. • These agents cause the blood vessels in the lungs to

hemorrhage and fluid to build-up until the victim chokes or drowns in their own fluids.

• A smell or lung irritation give warning of the presence of these agents, which are most dangerous when inhaled.

• Reactions may be immediate or delayed, with symptoms seen in seconds or delayed up to three hours after exposure.

• Phosgene (CG as designated by the military) is a common industrial chemical with a moderate lethal dose

• Chlorine gas is a common example of a choking agent that is frequently transported in bulk within the transportation system.


Chlorine• Description

– At room temperature, yellow-green gas with a pungent irritating odour.

– Only slightly soluble in water, but on contact with moisture it forms hypochlorous acid (HClO) and hydrochloric acid (HCl).HClO readily decomposes, forming oxygen free radicals.

– Not explosive but reacts or forms explosive compounds with other substances (e.g. NH3, acetylene)

• Routes of exposure– Inhalation– Skin/Eye contact


Phosgene

• Attractive as chemical weapon because of ease of availability

• Description– At room temperature, colourless,

nonflammable gas with a suffocating odour like new mown hay.

– Odour threshold is five times higher thanpermissible exposure level.

• i.e. Odour provides insufficient warning of toxic levels

• Prolonged severe exposure more likely than with Cl2


Phosgene

– At < 8 degrees C, colorless fuming liquid– Combustion product of many household

products that contain volatile organochlorinecompounds. (household solvents, paint removers)

Routes of exposure– Inhalation– Skin/Eye contact


4. Blood Agents

• Blood Agents are not persistent but are quickly fatal when inhaled. They initially cause headache, nausea, and vertigo, as they interfere with oxygen use at the cellular level.

• Cyanide based compounds are the main components of the blood agents

• Rapid rate of evaporation

• Example: Hydrogen Cyanide (AC)


5. Riot control agents

• Riot-Control Agents are not persistent. They include pepper sprays and tear gases. While riot-control agents are rarely fatal, they may be used along with more harmful agents, diverting attention from the more serious agents.

• Irritants• Hallucinogens (e.g. BZ)• Vomiting agents (e.g. Adamsite)


• Description– All are solids and require dispersion device to aerosolize

particles

• Routes of exposure– Inhalation

– Skin/Eye contact

– Ingestion


Psychochemical and incapacitating agents

• In concentrations likely to be encountered in the battle field, these chemicals make personnel ineffective for a varying period of time with out causing permanent harm.

• Hence they are non-lethal.

• Their ID50 must be less than the typical LD50. Thus LD50 = 50 X ID50


Physiological action• Psycho-chemicals incapacitate by attacking the enzymes of the

central nervous system located in the brain.• Monoamine oxides in the brain regulates the balance of the

neuro-hormone serotonin by oxidizing it to in active products.• Serotonin controls the mental processes.• If serotonin balance is too high, symptoms of mental

disturbance appear. • These take the form of excitement, anxiety, hallucinations,

distortion of vision and schizophrenia.• Tranquilizers combined with serotonin neutralizes it restoring

the mental balance.• Overdose deplete the serotonin balance and incapacitate by

inertia and sever depression.


MEDIAN DOSE • LD50 - MEDIAN LETHAL DOSE of a chemical agent

absorbed on skin or any route (mg/man)• ID50 - INCAPACITATING DOSE of a chemical agent

absorbed on skin or any route (mg/man)• LCt50 -MEDIAN LETHAL CONCENTRION, (concentration

of chemical agent x time of exposure)• ICt50 - MEDIAN INCAPACITATING CONCENTRATION,

(concentration of chemical agent x time of exposure)• ED50 - EFFECTIVE DOSE, mg/man


Advantages of chemical weapons

• Inexpensive to produce

• Multiple means of delivery

• Psychological as well as physical impact


BIOLOGICAL AGENTS


BIOLOGICAL AGENTS• Biological weapons are any infectious agent such as a

bacteria or virus when used intentionally to inflict harm upon others.

• Biological warfare agents include microorganisms bacteria, protozoa, rickettsia, viruses, and fungi.

• Biological weapons are immensely destructive. In the right environment they can multiply, and so self-perpetuate. And they can naturally mutate,

• May be directed at humans, plants, animals, and be a threat to crops, livestock, food products (agroterrorism) during processing, distribution, storage and transportation which could cause illness and also have severe economic consequences such as bovine spongiform encephalopathy, and foot and mouth disease.


BIOLOGICAL AGENTS• Like other threat agents, Bio-Agents can cause disease by

inhalation, ingestion, or skin contact. • But unlike other agents, biological agents can also be

contagious among people, and between people and animals.

• Bio-Agents may also incubate and multiply in the body for days to weeks before symptoms are seen and a person knows they are sick.

• For some Bio-Agents, no vaccines are available, so infected people must be quarantined.

• When left in the environment, some biological agents can be dormant but potent for periods of weeks to years, depending upon both the specific agent, and on the environmental conditions.


BIOLOGICAL AGENTS• There are three basic types of bio-agents: bacteria,

viruses, and toxins. • Bacteria are single celled organisms. They can reproduce

in a host, but bacterial bio-agents typically do not reproduce well in an open environment.

• In contrast, viral agents live in cells and can only reproduce in a host. The common cold is an example of a virus.

• Specific antibiotics have been developed to inhibit or destroy specific bacterial agents, and antiviral agents inhibit some viruses.

• Viruses are also controlled with vaccines, which help the body’s immune system identify and fight invading viruses.


BIOLOGICAL AGENTS• Effective treatments have not yet been developed for all

viruses (as exemplified by the common cold).

• The last group, biotoxins, are toxic chemicals that are produced by biological organisms, such as bacteria or plants. Ricin, for example, is a biotoxin that is produced by the castor plant. Toxins are treated with antidotes.

• All biological agents are produced in biological cultures.

• The steps involved in growing, purifying, and effectively dispersing sufficient quantity of a biological agent in manner that causes harm to many people takes technical skill and time.


BIOLOGICAL AGENTS• Advances in bioengineering raise the possibility of altering

a bio-agent’s characteristics to make it more dangerous, but this requires costly research and development, so the use of bioengineered agents is generally considered to be less likely.

• For increased effectiveness and confusion, an attack may include a mix of several different bio-agents, or bio-agents mixed with a chemical or radiological agent.


Operational classification

• The classification of biological agents in accordance with the operational effects is as follows:

• Lethal and transmissible

• Lethal and non-transmissible

• Non-lethal(incapacitating) and transmissible

• Non-lethal(incapacitating) and non-transmissible


Characteristics of biological agents

1. Infectivity- is the ability to cause disease. Greater infectivity means that fewer micro-organisms are required.

2. Virulence- different strains of the same microorganism may produce disease of different severity. The most virulent strain produces the most acute or severe effects.

3. Incubation- the incubation period is the time between the infective penetration and appearance of the symptoms of the disease. It is normally not less than 24 hours.


Characteristics of biological agents

4. Transmissibility- some microorganisms produce disease which may be transmitted from man to man (e.g. plague) which may cause an epidemic, while others, like anthrax do not.

5. Lethality- some microorganisms will produce disease which are usually lethal, if the target population is not immunized(e.g. small pox). Others will give rise to disease which are incapacitating rather than lethal(e.g. influenza).


Advantages Of Biological Weapons

antages Of Biological Weapons Multiple Methods For Delivery Wide Utility - non-discriminating, cause sickness,

death, panic, may disseminate widely, may be persistent

Good Logistics - cheap to make and store Versatile - can be in small or large quantities Defence May Be Difficult Cause No Damage To Infrastructure Easy To Conceal


Desirable Characteristics for Biological Agents

• Generate high levels of panic among population.

• Easy to obtain, Inexpensive, and Easy to produce in mass quantities

• Can be relatively easily “weaponized” or altered for maximum effect (even with genetic manipulation)

• High infectivity and High mortality• High person-to-person contagion


Desirable Characteristics for Biological Agents

• Lack of effective treatment• Need for intensive care, straining resources• High potential for casualties/morbidity• Result in lengthy illness with prolonged care

needed• Non-specific symptoms, especially early, delaying

recognition• Long incubation periods• Hard to diagnose• Great degree of helplessness from effect


Bio-Agent Delivery • Form of delivery, or method of dispersion, effects both agent

spread and response.

• Attacks may be either overt or covert.

• In an overt attack, the delivery method is obvious, such as release from an airplane or bomb.

• While the use of a bio-agent may not be immediately known, testing can quickly confirm the presence of microorganisms.

• But, determination of the name of the bio-agent can several days.

• For a biotoxin, as with any chemical, identification is much quicker.

• In a covert attack, the delay in identification of the bio-agent may be even longer because the attack may not be recognized until after people have become obviously sick, which may take days.


Bio-Agent Delivery • Covert attacks may include contamination of a

building or food, water, or other surfaces. • For contagious agents, the presence of an infected

individual in a large crowd can effectively spread a bio-agent.

• However, for most diseases, people are obviously sick, and bed-ridden during the most contagious stages.

• An unrecognized attack using a contagious agent with several days delay until symptoms are seen can allow further dispersion of infected people and spread the agent.

• In a worst-case-scenario, an epidemic may occur before a biological attack is recognized.


Bio-Agent Dose

• A tiny quantity of a Bio-Agent can cause sickness and death.

• The amount of a biological agent that can cause sickness varies with both the type of agent and the route of exposure (i.e., inhalation, ingestion, skin exposure).

• For some biotoxin, the amount needed to cause sickness is less than the weight of a small grain of sand.


Bio-Agent Detection• Bio-agents are detected through symptoms of infection

and through time-consuming tests. • Bio-agents cannot be detected by the human senses,

although high amounts of mist or powder can be seen and may be early indications of the presence of bio-agents (e.g., powder in envelopes).

• There are some instruments that can rapidly detect an increase of biological organisms in the air, but these instruments cannot identify the organism.

• An organism’s ability to cause harm is not certain until it is identified.

• Tests for identifying bio-agents typically take days because they require growing the organism in a culture before it can be identified.


Bio-Agent Response• Identify: Bio-Agent(s), source, area affected,

population exposed• Notify local medical facilities• Isolate and contain affected areas and

population• Treat -- provide vaccine or medications to the

affected population• Decontaminate affected areas and population• Follow-on Treatment -- continue medical

treatment as appropriate


Differences between biological, nuclear, and chemical agents,

• To summarize the general differences between biological, nuclear, and chemical agents:

• The effects of chemical and nuclear agents are typically recognized within minutes to hours after a release, while it may be anywhere from a couple days to a week before the effects of a biological attack are seen as symptoms.

• After a biological attack is recognized, it may take several additional days to confirm the type of biological agent.


Differences between…• With respect to the potential impact of an attack in

terms of the size of the geographic region in which health effects are seen, chemical attacks are unlikely to have health effects beyond 10’s of miles, and are more likely to be restricted to several city blocks.

• An extreme nuclear attack may have health impacts for hundreds of miles, while the more likely range of a dirty bomb is within 1 or 2 square miles. For a biological attack, the range may vary from local for non-contagious agents, to global for a highly contagious agent.


Differences between…• However, it is relatively difficult to obtain bio-

agents of the purity and quantity to affect many people.

• For nuclear agents, large quantities, such as in nuclear weapons, are extremely difficult to obtain because of the level of protection of this material.

• Smaller quantities, such as found in commercial or university equipment, may be easier to access, but these small amounts could not affect as great an area.


Differences between…• In contrast, many chemical agents are

commercially available, making a chemical attack perhaps the easiest to carry out.

• The nature of risk is that while the most likely types of events over an extended time may be predicted, the next single event type cannot be well predicted, thus, all credible event types must be given serious consideration and response planning, regardless of their relatively likeliness to occur.


End

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chemical agents (1)

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