Toxins as mass-casualty weapons

[Gregory]

quot;Toxinquot; is often loosely used to refer to any poison, but technically refers only to a poisonous chemical produced by an organism (although some toxins can now also be produced synthetically). Because toxins used as mass casualty weapons do not include the infectious agents from which they are derived, they do not replicate in the body and are not transmissible from person to person (see table CDC High-Priority Biological Agents and Toxins). Thus, toxins are more like chemical agents than biological agents; they cause poisoning rather than infection.
Hundreds of toxins are known. However, because of difficulties in isolating sufficient quantities, and problems with dissemination or environmental fragility, most toxins are more suited to assassination than to production of mass casualties. Only 4 toxins are considered high-threat agents by the US Centers for Disease Control and Prevention (CDC):

Botulinum toxin
Epsilon toxin from Clostridium perfringens
Ricin toxin
Staphylococcal enterotoxin B

Of these, only botulinum toxin is classified among the highest-priority agents. Epsilon toxin from C. perfringens is mainly of historical interest as an agent reportedly developed by Iraq in the 1980s; its main action is to increase capillary permeability, especially in the intestine.
(See also Overview of Incidents Involving Mass-Casualty Weapons.)