One of the reasons that we are prepared is that we are familiar with these poisons. Unfortunately, we've dealt with them before. Biological and chemical agents have been used as weapons throughout history. Historical perspective helps us to understand how biological and chemical agents have evolved from being used as weapons against soldiers in war to emerging as weapons of mass threat to civilians:
Today, these weapons still pose a threat on the battlefield, but may also menace civilian populations. However, it is important to place the actual risk of exposure to these agents in perspective.