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Chemical agents differ from biological
agents in a number of significant ways. To begin with, the onset
of symptoms may occur instantly or within a few hours of exposure,
whereas biological agents can take up to weeks to present. Chemical
agents are synthesized through some type of industrial process,
whereas biological agents are either self-replicating microbes or
compounds formed by these microbes such as botulinum toxin (produced
by Clostridia; see Chapter 17) or ricin,
a natural metabolic product of the castor bean plant, Ricinus communis. Chemical agents act
by disrupting normal metabolic function at varying sites throughout
the body according to the type of agent used and are categorized
into roughly eleven categories (Table 21–1). From a weapons
standpoint, not all chemical agents pose a threat as a likely choice
for terrorism or as a WMD. In large part this is because of logistical
or technical considerations—some require too much volume
for easy concealment, others pose difficulties of dispersal, and
others require such quantity as to be impractical for small, poor
groups with limited technical or financial resources.
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One of the considerations that makes chemical weapons a legitimate
threat is the sheer number of chemicals that, if used in the “right” way,
could function as a weapon. These agents could also be used in combination,
potentially increasing their potency, or altering physical properties
such as to volatility in order to augment abortion. The most likely
means of disseminating chemical agents are sprays, or through detonation
of explosives. Spraying distributes the chemicals more efficiently.
They are often classified according to how well they dissipate once
released, that is, persistent or nonpersistent agents.
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The signs and symptoms for many of the agents are nonspecific
and may be difficult ...