The clash between police and protestors in Ferguson, Missouri has escalated significantly over the past few days. Police dogs and handguns have been swapped out for tanks and assault rifles.
The protestors are being shot at with rubber bullets and wooden baton rounds, but perhaps the most disturbing images surfacing are those of police suppressing peaceful assembly with tear gas. Currently banned for use in international warfare, tear gas is still legal to use domestically, and has become a go-to for riot control.
To understand what the use of tear gas means for the citizens, members of the press, and government officials currently in Ferguson, here is a scientific explainer of what tear gas is, what it does, and what scientists and medical professionals think of its use.
What is tear gas?
Tear gas can refer to several chemical agents which stimulate the corneal nerves in the eyes. Formally referred to as “lacrymatory agents” (lacrima = tear in Latin), these chemicals are considered non-lethal weapons designed to disperse crowds by causing temporary pain and tearing. The most commonly used tear gasses are pepper spray (OC gas) and CS gas, though evidence from the ground in Ferguson suggests the police there are using the latter.
Most tear gasses are not a gasses at all, and are instead aerosolized solids. The CS gas grenades being used by the Ferguson Police Department contain CS (2-Chlorobenzalmalononitrile). CS was discovered in 1928 by scientists Carson and Stoughton (hence the name, “CS”), though it wasn’t until the 1950s and 1960s that CS was tested and developed for use. It has recently become popular because, while extremely effective, CS is considered significantly less toxic than alternatives.
Despite it’s “non-toxic” reputation, CS is prohibited for use in warfare by the Chemical Weapons Convention that was signed by many countries (including the US) in 1993. It is classified as a chemical warfare agent. However, this does not apply to domestic use of it or any tear gas, and police use of CS is legal in many countries, including the United States.
How it works
The effects of CS can vary widely and are dependent on the dosage received, duration exposed, and whether the chemical is packaged as a volatile solution or used as an aerosol. “Tear gases are nerve gases that specifically activate pain-sensing nerves,” explained scientist Sven-Eric Jordt, who studies the effects of tear gas and other chemicals at Yale University School of Medicine, in an interview with National Geographic last year.
Though this sounds extreme, medical professionals have concluded that CS gas poses little danger when used appropriately. “No consistent adverse effects from acute exposure have been documented, nor has excessive or unfounded use been a problem,” says Kari Blaho, research director for the Department of Emergency Medicine and Clinical Toxicology at the University of Tennessee.
After exposure, the effects of CS are generally felt within 60 seconds. The most immediate effects are irritation of the eyes, skin and mucous membranes, leading to burning sensations, tearing, coughing, and, if swallowed, vomiting. Burning of the skin, excessive fluid production in the eyes, nose and throat, disorientation and dizziness are common.
Most of these subside within an hour if the exposed individual is removed from the scene into a well-ventilated area and removes clothing contaminated by the chemical. However, severe reactions to the chemical have occurred, and include blistering, irreversible damage to the eyes, heart and liver damage, respiratory distress, and heart failure. People with asthma or otherwise weakened respiratory systems are particularly at risk of life-threatening complications. While there are no confirmed fatalities from CS exposure, tear gasses in general have had lethal effects, and CS specifically has been implicated in at least one death during an aggravated arrest.
Medical opinion on its use
Not all professionals agree that CS is safe enough for domestic use. “Tear gas under the Geneva Convention is characterized as a chemical warfare agent, and so it is precluded for use in warfare,” explains Jordt, “but it is used very frequently against civilians. That’s very illogical.”
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