What Is Tear Gas? Side Effects of 'Chemical Warfare Agent' Used on Migrants at Border

Border Patrol agents fired tear gas at members of the Central American migrant caravan who rushed the fencing that separates the U.S. and Mexico on Sunday.

As images of mothers and children choking on tear gas emerged, protesters and human rights groups decried the use of the chemical agent. 

Although tear gas is considered a chemical warfare agent, prohibiting its use in war, it is regularly used against civilian populations around the world, according to National Geographic. 

Exposure to tear gas causes severe eye pain, leading to the secretion of tears and mucus, New York Magazine reported.

The Centers for Disease Control and Prevention noted that exposure to riot control agents, including chemicals commonly known as tear gas, could result in symptoms affecting the eyes, nose, mouth, lungs and skin. In addition to potential blurred vision, difficulty swallowing,  shortness of breath, and rash, riot control agents could also lead to nausea and vomiting. People with asthma can have a particularly dangerous response to tear gas exposure.

"Tear gases are not really gases; they are solids or liquids that get turned into aerosols. There are a number of chemicals used that are called tear gas," Duke University anesthesiology professor Sven Eric Jordt told National Geographic in 2013. "Tear gases are nerve gases that specifically activate pain-sensing nerves. Spelled out like that, people can better compare them to other nerve agents out there. That's the major discovery we made, that they are not benign or just irritants."

GettyImages-1065219916 Central American migrants cover their faces after the U.S. Border Patrol threw tear gas to disperse them on November 25. GUILLERMO ARIAS/AFP/Getty Images

There is not yet a large body of research into the long-term health effects of tear gas, but some evidence indicates that exposure could have serious, prolonged impacts.

A Turkish study cited by the CDC, which included 93 males frequently exposed to tear gas and 55 unexposed subjects, found that the subjects who were exposed to tear gas were at greater risk of developing chronic bronchitis.

Epidemiological studies by the U.S. Army that analyzed the health effect of tear gas in more than 6,000 Army recruits exposed to the chemical during gas-mask training found "unexpected respiratory risks linked to tear gas exposures.This relatively young and healthy population developed a high risk of presenting with acute respiratory illness in the time after exposure, with increasing risk at higher exposure concentrations." 

Other evidence indicates less serious long-term impacts from tear gas exposure. One study of 34 young adults exposed to tear gas "in a confined space during a confrontation with the police reported no long‐term" consequences. 

But a number of people have died following exposure to high concentrations of tear gas in enclosed areas. "Deaths and respiratory tract injuries were reported after release of tear gas in prisons," the CDC said.

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