Chemical Warfare Agents

Additional scientific description

Chemical warfare agents represent a significant threat due to their potential for mass casualties and long-term environmental and health impacts. Munitions, devices and other equipment specifically designed to deliver toxic chemicals also fall under the definition of chemical weapons. Dual-use chemicals also classify as chemical warfare agents. These are any chemical that has legitimate peaceful uses, but which may also be used to make chemical weapons, for example, thiodiglycol is an ingredient in pen ink that can also be used as a precursor to mustard agents. Equipment in certain chemical production facilities can even be considered dual use in the sense that it may be converted to produce chemical weapons or their precursors. (OPCW, 2024d) The Chemical Weapons Convention (CWC) prohibits the use of toxic chemicals and their precursors and also covers toxins of biological origin; it also covers munitions or devices, and equipment directly in connection with these. The relevant toxic chemicals are listed in the Chemical Weapons Convention's Annex on Chemicals (OPCW, 2024b) and, in principle, the understanding and application of a so-called 'General Purpose' Criterion (GPC) and include (OPCW, 2024a):

• Blistering agents: These toxic compounds act via inhalation and contact, affecting the eyes, respiratory tract, and skin, first as an irritant and then as a cell poison. Exposure to blister agents causes large and often life-threatening skin blisters which that resemble severe burns, and often results in blindness and permanent damage to the respiratory system. Examples include mustard gas (ICSC 0418, 2005).
• Blood agents: These agents inhibit the ability of cells to transfer and use oxygen, effectively causing the body to suffocate. Blood agents generally enter the body through inhalation and are distributed via the blood. Examples include hydrogen cyanide (ICSC 0492, 2018) and cyanogen chloride (ICSC 1053, 1999).
• Choking agents: Inflicting injury mainly on the respiratory tract, choking agents irritate the nose, throat, and especially the lungs. When inhaled, these agents cause alveoli (air sacs in the lungs) to secrete fluid, essentially drowning those affected. Chlorine (ICSC 0126, 2009) and phosgene gas (ICSC 0007, 2013) are examples.
• Nerve agents: Nerve agents block impulses between nerve cells or across synapses and are highly toxic, with rapid effects. They act primarily by absorption through the lungs and skin, inhibiting the action of critical enzymes required for the normal functioning of the nervous system, causing seizures, loss of body control, muscle paralysis (including heart and diaphragm), and ultimately death. Sarin and VX gas are examples.
• Riot control agents: These agents are utilizsed to temporarily incapacitate a person by irritating the eyes, mouth, throat, lungs and skin, as well as constricting the airways. They are only considered chemical weapons when used in warfare. States can possess these agents for domestic law enforcement purposes, but if they are a member CWC, they must declare which type of agents they have. Examples include tear gas and pepper spray.

Metrics and numeric limits

The Chemical Weapons Convention (OPCW, 2024b, c) categorizes chemical substances into three schedules based on their potential for use in chemical weapons and their toxicity. Schedule 1 chemicals have no or very limited legitimate uses and have strict controls and verification measures. Schedule 2 chemicals have legitimate uses but can also be used as chemical weapons. Schedule 3 chemicals are precursors used in the production of chemical weapons. Parties to the Chemical Warfare Convention must declare any past or current chemical weapons-related activities and facilities, which are verified by the OPCW.

Whilst the Biological Weapons Convention (UNODA, 2021) does not have specific numerical limits, it prohibits the development, production, acquisition, transfer, and stockpiling of biological agents or toxins for hostile purposes.