Use for the instruments of destruction - not the act. Biological weapons are are organisms or toxins that can kill or incapacitate people, livestock and crops. The three basic groups of biological weapons that would likely be used are bacteria, viruses and toxins. Most biological agents are difficult to grow and maintain. Many break down quickly when exposed to sunlight and other environmental factors, while others, such as anthrax spores, are very long lived. Biological agents can be dispersed by spraying them into the air, by infecting animals that carry the disease to humans and by contaminating food and water.