Building protection
Threats, biochemical weapons, nerve agents

Biological aerosols

Biological Warfare Agents
Biological agents are defined as live organisms, or toxins that are derived from live organisms, that are disseminated with the intention of causing disease in the target population. The difference between the chemical weapons and the biological weapons is that the chemical agents cause direct injury; the biological weapons cause disease, which results in injury.

Biological weapons may be selected from

Bacteria
The most widely known of disease causing agents. They include some of the most widely touted of biological agents, including anthrax, and plague (the Black Death) meliodosis, brucellosis, tularemia, and cholera.

Bacteria can be killed and controlled by disinfectants, boiling, and destroyed by sunlight. Some forms however, such as anthrax and tetanus, are transformed into spores which have a great resistance to disinfectants, boiling, and sunlight. Low temperatures and freezing do not affect bacteria. Bacteria are visible only under a microscope, since their size ranges from 0.5 to 5.0 microns.

Viruses
Probably the group of pathogens that people are most aware of today, they include the agents causing AIDS, hepatitis C, smallpox equine, encephalomyelitis, denque fever, yellow fever, and psittacosis. These microbes are the smallest organisms. Their size is approximately a hundred thousand times smaller than bacteria and they cannot be seen using an ordinary microscope. Unlike bacteria, viruses require living tissue to multiply. Viruses are also resistant to drying and freezing.

Rickettsiae
Ricettsiae are a group of bacteria that have to live within a host cell. The diseases caused by rickettsia that may be dispersed as a result of biological weapons are: Typhus, Q fever, Rocky Mountain Spotted Fever, and Tsutsugamushi disease. These microbes are approximately the same size as bacteria but require infected tissue to survive and reproduce.

Yeasts and fungi
The fungi that cause diseases are: coccidial mycosis, nocardiosis, and blastomycosis. Fungi are like bacteria but are resistant to sunlight and more resistant to disinfectants.

Toxins
The toxins that cause disease that may be dispersed during wartime as a result of biological weapons are: botulism, tetanus, and diptheria. Some microbes themselves are not poisonous but produce toxins that are. Microbes that produce toxins that are poisonous are listed above. Although there are over l,000 toxins that are able to produce damage to people, animals, and plants, only a few can be delivered as biological weapons. Table 1 shows the mouse LD50s (lethal dose to half of the exposed) of some toxins and nerve agents.

Table 1. Comparative lethality of selected toxins and nerve agents in laboratory mice.

Agent	LD50(µg/kg)	Molecular weight	Source
Botulinum Toxin	0.001	150000	Bacterium
Shiga Toxin	0.002	55000	Bacterium
Tetanus Toxin	0.002	150000	Bacterium
Abrin	0.04	65000	Plant
Maitotoxin	0.10	3400	Marine dinoflagellate
Palytoxin	0.15	2700	Marine soft coral
Ricin	3	64000	Plant (castor bean)
Saxitoxin	10	299	Marine dinoflagellate
VX	15	267	Chemical agent
Soman (GD)	64	182	Chemical agent
Sarin (GB)	100	140	Chemical agent
T-2 Toxin	1210	466	Fungal mycotoxin