The chemical weapon that is not actually a gas
Often used by police to disperse crowds, tear gas is a misnomer. These substances are actually aerosolized solids or liquids that irritate your mucous membranes. While often viewed as a non-lethal tool for riot control, the physical and long-term health consequences can be unexpectedly severe.
Technically, tear gas is a group of lachrymatory agents—from the Latin 'lacrima' for tear—that stimulate the nerves of the lacrimal gland. Rather than true gases, these agents are typically aerosolized solid or liquid compounds, such as bromoacetone or xylyl bromide, dispersed via grenades or sprays. The most common agents used today are CS and CN. While CS is a potent irritant that can cause respiratory burning and involuntary eye closure, its effects often resolve within minutes of breathing fresh air. In contrast, CN is a primary component of the branded self-defense spray Mace and primarily targets the eyes.
The history of these agents is rooted in the brutality of World War I. In August 1914, the French deployed ethyl bromoacetate, followed by German 'ni-shells' in October 1914, and xylyl bromide against Russian troops in January 1915. Although international treaties like the 1925 Geneva Protocol prohibit the use of such substances in interstate warfare, their use in domestic law enforcement remains widespread. However, the distinction between 'non-lethal' and 'lethal' is often blurred by the physical mechanics of deployment; canisters can cause skull fractures or even death if they strike a person directly.
The medical reality is complex and often undocumented due to low-quality peer-reviewed evidence. While many effects are transient, exposure can lead to serious complications, including chemical burns, permanent corneal scarring, and respiratory illnesses. In some instances, such as the 2019–2020 Chilean protests, individuals suffered permanent loss of vision. There is also significant concern regarding the use of expired canisters; Venezuelan chemist Mónica Kräuter found that 72% of canisters used by authorities in Venezuela were expired, potentially breaking down into dangerous substances like phosgenes and cyanide oxide.
Source: Tear gas
