Chemical, Biological, or Radiological Threats Biological threats may include the following types of substances. Chemical Any substance designed or intended to cause death or serious bodily injury through the release, dissemination, or impact of toxic or poisonous chemicals, or their precursors, such as mustard gas, nerve agents, and sarin gas. Biological Any substance involving a disease organism, such as smallpox, botulinum toxin, anthrax, and ricin. Radiological Any substance designed to release radiation.