Tear Gas: the chemical warfare agent used on demonstrators in Ferguson

By Christie Wilcox | August 14, 2014 3:09 pm

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.”

“The possibility of long-term health consequences such as tumor formation, reproductive effects and pulmonary disease is especially disturbing in view of the multiple exposures sustained by demonstrators and non-demonstrators alike in some areas of civil unrest” wrote Howard Hu and five other medical doctors in the Journal of the American Medical Association in 1989. “The evidence already assembled regarding the pattern of use of tear gas as well as its toxicology raises the question of whether its further use can be condoned under any conditions.” The doctors came down hard on current police use of the substance:

“In many instances in which harassing agents have been used, dialogue and negotiation could have been pursued. Often, public order might be better served if riot police are not called immediately to duty. It is the hallmark of repressive regimes to equate the voicing of dissent with disorder and to deny opponents the freedom of assembly and speech, rights guaranteed universally among signatories to the Universal Declaration of Human Rights.”

Mani Prasad Gautam, a doctor with the National Academy of Medical Sciences in Nepal, and his colleague echoed similar sentiments in a 2004 article on the use of tear gasses. “Although the chemical agents have been used for many years, the full extent of effects on health is far beyond our understanding,” they wrote. “The use of these gases as per the safety sheet provided by manufacturers is not always the rule in real scenario. Even with strict guidelines regarding chemical weapons, it is nearly impossible for police officers to monitor their use during an actual deployment.”

They also point out the medical burden of exposure, which is often ignored by those who deploy tear gasses. “Neither the police nor the government hospitals take any responsibility for aftercare of the exposed people,” they stated. “Unless there is independent research establishing that these weapons are reasonably safe, and until there is credible oversight of the police practices and manufacturers’ claims, the public has no way to assess how much risk it is accepting in the name of law and order.”

They conclude, quite strongly:

“The use of CS gas and other tear gases with comparable clinical effects should be taken as tantamount to chemical warfare against civilians and, therefore, the use of these agents against human populations everywhere should be banned.”

 Tear gas in Ferguson

The chief of police in Ferguson, Tom Jackson, has defended his department’s use of tear gas and other riot suppression measures. “There are complaints about the response from some people, but to me, nobody got hurt seriously, and I’m happy about that. I’m happy that nobody got hurt,” Jackson said at a press conference today.

Though the science of tear gas use is mixed, it is generally considered safe. But that does not absolve police of improper or over use of tear gasses under any circumstances. In Ferguson right now, there are reports of police using tear gas on peaceful protests led by government officials. The police are accused of targeting the press with tear gas to silence the media. In these cases, it doesn’t matter whether CS is safe — the violation of First Amendment rights cannot be tolerated. Though the events might be occurring in Ferguson, Missouri, questions surrounding excessive force and constitutional rights are echoed throughout our nation. This is our country, our America, which was founded on the principles of liberty and justice for all. We all must defend those principles.



MORE ABOUT: CS, Ferguson, Tear Gas
  • Buddy199


    I particularly like the tweet from Gaza terrorists offering advice. I’m sure Al Sharpton will get to the bottom of all this.

    Speaking of defending our Constitutional rights, who’s going to defend us against a government that uses the IRS as a hammer against its political opponents?

    • http://jonathan-peterson.com/ Jonathan Peterson

      right. because using keywords to help determine whether an applicant for 501c3/4 status primarily exists for political reasons, is EXACTLY the same as police killing unarmed citizens and using military force on peaceful protestors.

      • Buddy199

        The subversion of the most powerful government agency next to the armed forces by political hacks is chilling. How bad is it? Imagine how you would feel if it was done by President Cheney or Cruz. The part where they didn’t do anything wrong but conveniently destroyed their hard drives is very comforting as well.

        I don’t know. Maybe if there weren’t rioters throwing molotov cocktails at the police there wouldn’t be a need for crowd supression. How do you avoid getting gassed? Stay away from riots.

        • http://jonathan-peterson.com/ Jonathan Peterson

          why is it that you blame the victims when the police are firing rubber bullets and posting snipers, but you blame the government when political organizations application for tax free status, which allows them to hide their donors identities is reviewed because of keyword searches?

          Most powerful agency next to the armed forces? How many unarmed people has the IRS shot in the last week?

  • twiz1

    The coverage of this thing has been awful. I have been following it and I still don’t know if the riots came fist or the riot police came first. If the riot police came first then the police are likely at fault for the riot itself. If the riot came first then I can hardly blame the police for following what is basically a standardized riot response. All I do know is that stealing wine from a convenient store…irrespective of what the police did or did not do is outrageous. I’d rather see them throwing bottles at the police than stealing from an innocent store owner who had the unfortunate luck to have his store located in the middle of a protest zone.

    To be clear I am not advocating attacking the police but at least they have a beef with the police. What did the store owner do to them?

  • Meh

    And today i heard, an American police officer shot his daughter during the night in his garage, because he thought it was a burglar. Hail to the shoot first think later attitude.

  • Lorie Franceschi

    One of these days…some idiot on either side is going to kick off what we all really think is going to happen. the second American Civil War and this time I do not think that the Government will win..

  • JH

    Well, it’ll be interesting to see what happens when there is actual evidence to weigh. It’s not clear to me that rioting is an appropriate response to an event for which almost all the available information is heresay.

    I can’t say I have much sympathy for people getting tear-gassed and rubber-bulleted. If you’re going to go out and “protest” during a riot, be prepared for the cops to get confused and treat you like a rioter. For goodness sakes, use some friggin’ common sense!

  • Dimitri Ledkovsky

    To the ‘elites’ most people are “useless eaters” and are dispensable. You didn’t know? One way to resist this crapola is to stop being a consumer of all the mainstream glop that is stuffed down our gullets every minute of our waking and sometimes sleeping hours.


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About Christie Wilcox

Dr. Christie Wilcox is a science writer based in the greater Seattle area. Her bylines include National Geographic, Popular Science, and Quanta. Her debut book, Venomous, released August 2016 (Scientific American/FSG Books). To learn more about her life and work, check out her webpage or follow her on Twitter, Google+, or Facebook.


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