Tear Gas 101: Why All The Crying?

On Sunday, November 25, 2018, Central American immigrants at the United States-Mexico border were sprayed with tear gas by U.S. Customs and Border Protection officials. Images of families with children have underscored the tragic nature of the conflict at the U.S. Southern border. Regardless of one’s political views, when children come in to harm’s way, the debate becomes even more heated.  The American Academy of Pediatrics issued a statement in response to tear gas being used at the border, which included the following:

The use of tear gas on children—including infants and toddlers in diapers— goes against evidence-based recommendations, and threatens their short and long-term health. Children are uniquely vulnerable to physiological effects of chemical agents. A child’s smaller size, more frequent number of breaths per minute and limited cardiovascular stress response compared to adults magnifies the harm of agents such as tear gas.

While most have heard the term “tear gas” being used in riots or in the military, the mechanism of how this substance works and how it causes temporary and/or permanent damage deserves some additional attention.  The chemical name for tear gas is ortho-chlorobenzylidine malononitrile, or CS. A similar chemical more commonly known as “pepper spray” used as a portable protection device, contains the substance oleoresin capsicum (OC).  Both serve the purpose of creating severe discomfort within seconds, primarily to the eyes, but also potentially to the mouth, nose, and skin.  Symptoms occur within 30 seconds, and can last 15 minutes or longer.  The agents are known as “lacrimators,” from the Latin lacrima, meaning “tear.”  The irritation to the eye leads to the classic tearing and bloodshot look to the white (sclera) of the eye.  Severe cases can cause visual loss and injury to the cornea.

CS, or “tear gas,” is actually not a gas, but a solid substance.  It does not dissolve in water, so it is turned into a gas by several techniques, either by grinding it into a fine powder, dissolving it in an organic solvent, or heating it in a grenade that converts it to a gaseous material. It most notably causes tearing, spasm of the eyelid muscles, coughing, throat irritation, and, rarely, skin blistering. Needless to say, its effects have not been studied in children, yet it is well known that any particulate matter, such as the recent airborne contamination from fires in Northern and Southern California, has a much more profound impact on the mucous membranes  and airways of children.

Oleoresin capsicum (OC), is an oil derived from pepper plants– thus the commonly known name of “pepper spray.” It acts by stimulating pain fibers to release a substance called “substance P,” which leads to pain response, swelling, and vasodilation (swelling of the blood vessels). Like CS, it causes a burning sensation of the eyes, mouth, and skin, and can also lead the recipient to feel short of breath. Pepper spray is most known for use in individual self-defense against a human or even an animal attacker. Its effects occur nearly immediately, and can last 15 minutes or longer. Mace is a particular brand of pepper spray, and may contain similar substances to OC.

Studies in adult subjects have examined potential antidotes to symptoms related to tear gas or pepper spray exposure, including irrigation with water and utilization of baby shampoo to neutralize the irritants.  There has been no substance or practice found to reduce the duration or severity of symptoms related to these agents.

The Geneva Convention declared tear gas to be a form of chemical warfare, and it is banned in such conflicts.  However, it is not banned in civilian situations, either by individual use of pepper spray, nor by law enforcement use in the form of tear gas.

Forbes – Healthcare