National Geographic News
A protester throws back to police a tear gas canister during clashes in Taksim square in Istanbul.

A protestor in Taksim Square in Istanbul throws a tear gas canister back at police on June 11, 2013.

Photograph by Kostas Tsironis, AP Photo

Brian Clark Howard

National Geographic

Published June 12, 2013

On Wednesday, hundreds of Turkish riot police forced thousands of protestors out of Taksim Square in Istanbul, by showering them with tear gas and blasting them with water cannons. The square has been ground zero for protests that started on May 31 with the goal to stop developers from cutting down trees—but the unrest has since spread to broader issues and at least 78 other Turkish cities, according to news reports.

Protesters have been calling for an end to the leadership of Prime Minister Tayyip Erdogan, citing what they call increasingly authoritarian measures, including restrictions on alcohol sales, separation of genders in schools, and other issues.

The Turkish Human Rights Foundation has reported that four people were killed in protests Tuesday and that nearly 5,000 people have been treated for injuries, including widespread exposure to tear gas.

Use of tear gas in warfare is banned by the international Geneva Convention, and its use on civilian populations remains controversial. A number of governments have used it to suppress Arab Spring protests (see photos) in recent years, causing injuries and some deaths.

In August 2012, Physicians for Human Rights released a report about Bahrain's use of tear gas against protesters at that time, stating, "The Bahrain government's indiscriminate use of tear gas as a weapon has resulted in the maiming, blinding, and even killing of civilian protesters, and must stop at once while the government reassesses the use of such toxic chemical agents."

The report documented the case of a person in Bahrain who suffered shortness of breath, wheezing, and difficulty speaking for two weeks after exposure to tear gas. Several women reportedly miscarried as a result of exposure to the agent, and a man with asthma died of acute respiratory failure after inhaling it.

To better understand the dangers of tear gas, National Geographic reached out to Sven-Eric Jordt, a professor of pharmacology at Yale University School of Medicine. In the early 2000s, Jordt discovered that tear gas works on the body by activating pain receptors.

Jordt had been exposed to tear gas himself in the 1980s, when he was a student in Germany and attended a protest against nuclear waste.

Can you give us a brief history of tear gas?

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.

Gases called CS and OC are used almost exclusively nowadays worldwide. OC is oleum capsicum (chili pepper oil), the active ingredient in pepper spray containing capsaicin, the highly pungent natural product. CS gas contains a chemical named 2-chlorobenzalmalononitrile, a highly electrophilic agent activating pain receptors. Other agents have been used in the past, including some that are illegal now due to toxicity. CN gas was used in Vietnam in the Vietcong tunnels.

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.

Tear gases were identified [and used] in World War I but without the knowledge of [how they work on] biology.

Can you summarize your lab's work on tear gas?

In 2006 and 2009 we published papers identifying a receptor for pain that is activated by tear gas, which causes the body's response: closing of eyes, a rush of pain, bronchial spasms that make it difficult to breathe, etc. Since then we have received funding from the National Institutes of Health to identify countermeasures to these effects, for acute and long-term exposures.

What have you learned about these new tear gas receptor blockers so far?

We haven't published this yet, but what we see is these blockers reduce the pain responses in animals, and also the inflammatory swelling of the skin exposed to tear gas. When tear gas is deposited on the human body, it can cause burn-like injury and swelling, especially [in] parts of the body that are more moist, like eyes and armpits.

These results have not made it into any clinical trials yet, but they are interesting for general pain medications, because these receptors are not just involved in tear gas response—they also respond to other painful stimuli and smoke irritations.

The receptors are designed to warn a human or animal about exposure to a noxious chemical, so the animal removes itself from the exposure. They increase survival.

Could such tear gas receptor blockers eventually be used by protestors?

It's hard to say; in principle, yes. But taking it before an exposure could be very dangerous. If you did not feel pain at lower levels of exposure, and therefore did not leave, it could lead to more serious burn-like injuries at higher levels of exposure.

Should tear gas be used on people?

I get asked this a lot. Tear gas under the Geneva Convention is characterized as a chemical warfare agent, and so it is precluded for use in warfare, but it is used very frequently against civilians. That's very illogical.

There are enough examples where people suffered severe injury and burns, especially in enclosed environments or city streets with several-story buildings. Residents who live near Tahir Square in Cairo that have gotten a lot of tear gas have had long-term exposure, leading to respiratory problems. Long-term exposure is very problematic.

People with asthma or other conditions can have very severe reactions. Tear gases are very serious chemical threats. I think it is very problematic to use them. Their use in Egypt and Turkey has been especially excessive and dangerous.

Law enforcement has to weigh the risk of tear gas injury of bystanders against gaining control in a riot situation, under the assumption that rioters break the law. Governments need to put in place immediate decontamination procedures for areas, and especially residences, when tear gas is used.

In the U.S. some activists have argued that their civil rights have been violated by use of tear gas against them. What do you think of cases like that?

In the U.S. law enforcement uses a lot of pepper spray, which also activates pain receptors and can have serious effects, but is not as toxic or severe as the classic tear gas that is being used in the Middle East.

I think it depends on the individual case, but these agents are certainly not benign. There is no way to disconnect the pain that is induced from the physiological inflammatory effects of these agents.

Doug Harvey
Doug Harvey

Or the author just doesn't know his a** from a hole in the ground.

Doug Harvey
Doug Harvey

This is a wildly misleading article.  Bob, we still train with tear gas in the military - and need to get re qualified annually in the gas chamber in the USMC.  Yes, Jesse, tear gas was used extensively in California against occupy.  And let's not forget Waco - where CS gas was used against women and children in an enclosed space killing many.  National Geographic didn't used to be so misleading.  I'm saddened by this.

Bob Griffith
Bob Griffith

Well, we trained with tear gas in the Army in the early 60's.  Dunno the particular chemistry for the stuff at the time, but it was "army issue".  In one exercise, a squad (9 men) was taken into a shed with our masks on.  Then a canister or two was released and dropped into an open barrel in the center, and the room then filled with "gas".  Next, we were instructed to take our masks off and calmly file out, hand to shoulder.  And as the squad leader, I was the last out.  Basically feels like sand in your eyes, but we were told not to rub them as that would exacerbate the irritation.  The objective was to simply experience the stuff, and not to overly fear it.  In fresh air, the irritation subsides in a few minutes.

Jesse Custer
Jesse Custer

@Brian Howard

Why do you make it sound like the U.S. doesn't use tear gas on protesters?

There isn't a single mention of the U.S. Using teargas, just a mention at the very end that they use "pepper spray" which is not as toxic or severe as the "...classic tear gas that is being used in the Middle East."

You make it sound like we differ from the middle eastern countries using teargas. But I was able to find the use of teargas by U.S. specifically california PD's, in less that 15 seconds with the use of a google/youtube search.

For example: Occupy Oakland protests garnered countless rounds of teargas used for the very same reason the middle east is using teargas. To quell unrest.

Why focus on foreign countries using the stuff and completely ignore the fact that the U.S. Government/PD's use it as well?  I mean your comment about pepper spray makes it sound like you are trying to say "the U.S. doesn't use tear gas".

Which is a bold faced lie, misleading, and knowledge which I'm sure you aren't lacking.

Dances Sky
Dances Sky

The line about "Use of tear gas in warfare is banned by the international Geneva Convention,"is definitely misleading.

Tear Gas was considered a "riot control agent" when the original Conventions were signed and ratified by the US Senate, which is the only way treaties become law in the US or in pretty much any other country that hasn't abdicated its soverignity to the EU. Tear Gas is only considered a "chemical weapon" under one of the amendments to the Convention as part of a parcel that was offered by the former Soviet Union in 1975 in order to set a world stage that would be more favorable to the revolutions it presumed it would be inciting/fomenting/supporting.

That package of amendments was not ratified by the US Senate nor by many other countries and Tear Gas is still considered a "riot control agent" in the US and in all those other countries.

Brian Howard
Brian Howard expert

Thanks for the comments! I was surprised as well that tear gases are technically considered chemical weapons.

Nancy Smith
Nancy Smith

and i thought only Saddam H was the only one using 'gas' on those pesky Kurdish upstarts! as benign as they are portrayed in most media news stories, the real pain here is how civy's are treated with less consideration than 'out and out' murderous war foes!   make's one wonder if we already are living under a 'police state', and have we truly being brainwashed by the capitalist/political US war machine ?

a watson
a watson

Appreciate the insights into these gases as well as the knowledge that these are considered "chemical" weapons by the Geneva Convention

Brian Howard
Brian Howard expert

@Bob Griffith Thanks for commenting. As I understand it, the U.S. Army has soldiers train against tear gas to help them become prepared for possible chemical threats.

Sources have told me they have treated veterans who do seem to suffer from long-term effects of exposure to tear gas, so there are likely risks that generals must weigh against preparedness.

Doug Harvey
Doug Harvey

@Bob Griffith We still do - using CS in the gas chamber, we need to re-qualify annually.  Never heard of lasting effects before this article.  Reeks of BS to me...

Brian Howard
Brian Howard expert

@Jesse Custer Hi. According to my research, recent actions in the Middle East have seen much more intense deployments of tear gas, and in denser areas, than has been seen in the U.S., so it was a matter of scale. 

I did ask the expert about tear gas in the U.S.--I put it as the last question because it's not what the focus of the story was--and he said pepper spray-based materials are more commonly used here nowadays. 

This was a Q&A with a relevant expert about a story in international news, it wasn't meant to be totally comprehensive of tear gas use in the whole world, though it's probably a good thing that people are talking about its use.

Doug Harvey
Doug Harvey

@Jesse Custer This is a poor article, indeed.  Nat Geo is going way downhill with this tabloid garbage.

Brian Howard
Brian Howard expert

@Dances Sky I did find this article on the US stance on Geneva Convention and Chemical Weapons Convention limitations on chemical agents. It suggests the Geneva Convention does not differentiate between “warfare agents” and “riot control agents”, but uses the terms “poisonous, asphyxiating and other gases”. If “other” includes tear gases has been a matter of debate and interpretation for decades.

Brian Howard
Brian Howard expert

@Dances Sky Interesting, sounds like how you define "Geneva Convention," and who you ask about it. 

I think the larger point that tear gas is frowned upon in military conflict still stands, according to my research. One source told me any use of tear gas in war would immediately arise suspicion that other chemical agents were also used, and therefore lead to escalation.

teddy bullard
teddy bullard

  Thanks Mr. Howard, for the article. To me, it is quite informative, if not enlightening. I am quite concerned about the chemical weapons claim against the government of Syria. Not saying that it didn't happen, but it certainly stands to be validated and confirmed beyond any reasonable doubt before committing resources to the "rebels". Seems that the "Commander-In-Chief" here in the U.S., is pre-disposed to getting involved in the conflict; and in my opinion, John McCain needs to sit down and be quiet for a while. One of the overbearing questions would be, as it should have been in Egypt: What kind of Government will take it's place? I think that most of the civilized world would agree that another bunch of hate filled terrorists wearing suits and ties, should not be welcomed.


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