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Identifying chemical and biological agents
Learn the characteristics of these substances and their effects
Chemical/biological agents are defined as toxic substances, pathogens or toxins
that are used to kill or incapacitate people, animals or plants, or to damage
equipment. The use of these agents dates as far back as 429 B.C. when the Spartans
ignited pitch and sulphur creating toxic vapors in the Peloponnesian War.
This article discusses the types of chemical and biological agents and their
effects.
Chemical Agents
Chemical agents are toxic sub-stances that cause incapacitation or death upon
exposure. There are four general types of "traditional" chemical agents-choking,
blood, blister and nerve-that vary in their toxicity, mode of action and effect.
To learn more view the chart on
"The characteristics for several of these common chemical agents"
Choking agents are the oldest known chemical warfare agents and have a corrosive
effect on the respiratory system. Breathing these agents causes pulmonary edema
where the lungs fill with fluid and choke the victim-also known as "dry
land drowning."
Choking agents are heavy gases and tend to stay close to the ground but tend
to dissipate rapidly in a breeze. Examples include phosgene and chlorine.
Blood agents were used to a limited extent in World War I. They are fast-acting,
highly poisonous chemicals. This class of agent inactivates the enzyme cytochrome
oxidase which prevents the normal uptake of oxygen by the cells, causing damage
to body tissues.
Blood agents are highly volatile and enter the body through the act of breathing.
In a gaseous state, they dissipate rapidly in the air. Examples include hydrogen
cyanide and cyanogen chloride.
Vesicant (blister) agents were initially used by Germany in World War I and
are casualty-producing compounds. Released as liquids, these agents cause painful,
debilitating blisters on exposed skin and can also affect unprotected eyes and
lungs. Effects occur within a few minutes to hours of exposure. The blisters
from sulfur mustard exposure heal very slowly and are more susceptible to infection
than chemical or physical burns. Examples include sulfur and nitrogen mustard.
Nerve agents are the most toxic chemical agents and can cause death within
minutes of exposure. They can be inhaled or absorbed through the skin. This
category is further broken down into G-series and V-series.
Discovered in the 1930s by German scientists, G-series nerve agents are organophosphorus
compounds that inhibit the action of the acetyl cholinesterase enzyme.
As a result, large amounts of the chemical acetylcholine build up within the
nervous system, which cause hyperactivity of the muscles and body organs stimulated
by these nerves. Examples include sarin, tabun and soman.
V-series nerve agents were researched by the British in the 1950s and are similar
to G-series nerve agents. However, they are more advanced than G-series agents
and are generally more toxic and less volatile. They also pose a greater skin
penetration hazard. An example of a V-agent is VX.
Industrial Chemicals
Although countries generally focus on traditional agents (choking, blood, blister
and nerve), terrorist groups may use readily available toxic industrial chemicals
as well. In fact, several compounds initially developed for military use in
wartime, such as phosgene and chlorine, are commonly used in industry today.
Examples include:
- Organophosphate pesticides--such as malathion and parathion. Chemically related to nerve agents but are not nearly as toxic. These compounds disrupt the acetyl cholinesterase enzyme just like nerve agents do.
- Carbamates--produce the same effects as nerve agents and organophosphate pesticides, but are not structurally related. An example is Sevin R.
- Metallic poisons--affect a person in a variety of ways and are usually inhalation or ingestion hazards. Arsenic trioxide is a metallic poison.
Biological Agents
Biological agents are live microorganisms or toxins that can incapacitate or
kill humans and animals, and damage crops. Biological warfare is the most economical
and easily concealed of the weapons of mass destruction (biological, chemical
and nuclear).
Members of the Japanese Aum Shinrikyo cult admitted to using biological agents
in Japan during the mid-1990s, further highlighting the increased danger of
biological warfare by terrorist organizations.
One of the most insidious aspects of biological agents is their extraordinary
potential for covert use. Biological agents are undetectable by the human senses
and can be readily released from stand-off distances. Clinical symptoms usually
do not appear for days to a week or more after an attack.
Since the biological agent attack may not be detected, initial cases of exposure
may not be attributed to it. This would make it extremely difficult to adequately
respond to exposure of a large number of people and to identify the culprits.
One disadvantage to the use of biological agents is that many are rapidly degraded
upon exposure to certain conditions in the environment, such as ultraviolet
and visible radiation, heat, drying or humidity.
Pathogens are living organisms that can cause diseases in humans. Pathogens
include bacteria, viruses and fungi and vary considerably in their lethality
and physiological effects. Toxins are also classified as biological agents
even though they are non-living substances. Click
here to view characteristics for several common biological agents.(pdf
chart)
Bacteria are single-cell organisms that can be grown and developed by terrorists.
Examples include Francisella tularensis and Bacillus anthracis, the cause of
tularemia and anthrax.
Viruses are submicroscopic organisms that require living cells to produce and
multiply. Variola major, the causative agent of smallpox, is a virus that could
be used as a biological agent.
Fungi usually do not affect healthy individuals but they can pose a significant
hazard to plants, such as food crops. Cereal rust is an example of a fungal
agent.
Toxins are metabolic by-products of living organisms, such as microbes, insects,
snakes and plants. They can also be artificially produced. Ricin, for example,
is a toxin extracted from castor beans.
The characteristics and effects of biological agents vary. Yersinia pestis,
the causative agent of the plague, has the potential to inflict epidemics,
while Bacillus anthracis (anthrax) spores can contaminate soil for decades.
Toxins can take effect within hours and most are more deadly than the
synthesized chemical nerve agents. Biological agents can be spread through
the contamination of food and water supplies or via aerosol dissemination.
An example of food contamination would be the use of Salmonella typhii
which produces symptoms similar to that of food poisoning.
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