Biological and chemical
weapons are easier than nuclear arms to produce
although they do require specialized scientific
expertise in order to be effectively used.
Biological agents are odorless,
tasteless and invisible to the human eye. Weight-for-
weight, they are hundreds to thousands of times
more potent than a chemical weapon,
according to the Center for Defense and International
Security Studies in the UK.
The Centers for Disease Control
and Prevention in the United States lists six
diseases as "high-priority" biological
agents that pose a risk to national security.
The CDC also describes more than
two dozen chemical agents that could be
used as terrorist weapons.