Biological agents: Living organisms or their derivatives that can be used in weapons to cause incapacitation or death. Biological agents have the ability to reproduce themselves, thus they are less predictable than chemical agents. Chemical agents: Chemicals that are harmful or lethal to humans and are used in war. Mustard gas: Chemical warfare agent that blisters skin and can be lethal in large amounts. Nerve agent: Chemical agent that disrupts the nervous system, leading to loss of muscular control and sometimes death. Phosphorous trichloride: A chemical that has industrial uses, but is also a component of nerve agents. Phosphorus oxychloride: A precursor of the nerve agent tabun. Precursor: A chemical that can be mixed or chemically combined with another substance to become a lethal agent. For example, the precursors methylphosphonic difluoride and pinacolyl alcohol produce the nerve gas soman when mixed together. Thiodiglycol (TDG): Chemical with wide industrial uses which is also a component of mustard gas. Toxins: Nonliving chemical substances produced by living organisms. Through biotechnology, toxins can now be reproduced synthetically.