Terrorists often use threats to create fear among the public, to try to convince citizens that their government is powerless to prevent terrorism, and to get immediate publicity for their causes. Domestic terrorism involves groups or individuals whose terrorist activities are directed at elements of our government or population without foreign direction. Biological agents can be dispersed as aerosols or airborne particles. Terrorists may use biological agents to contaminate food or water because they are extremely difficult to detect. Chemical agents kill or incapacitate people, destroy livestock or ravage crops.
Some chemical agents are odorless and tasteless and are difficult to detect.
Biological and chemical weapons have been used primarily to terrorize an unprotected civilian population and not as a weapon of war. This is because of fear of retaliation and the likelihood that the agent would contaminate the battlefield for a long period of time. The Persian Gulf War in 1991 and other confrontations in the Middle East were causes for concern in the United States regarding the possibility of chemical or biological warfare. While no incidents occurred, there remains a concern that such weapons could be involved in an accident or be used by terrorists. The bomb left a crater 200 by 100 feet wide and five stories deep.