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Protesters run from tear gas fired by police officers next to the Colorado State capitol in Denver, on May 30.
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The disturbing history of how tear gas became the weapon of choice against protesters

The chemical weapon was originally marketed to police as a way to turn protesters “into a screaming mob.”

Jen Kirby is a senior foreign and national security reporter at Vox, where she covers global instability.

It was a chilling split screen at the start of June: President Donald Trump preparing to give an address in the White House Rose Garden as dozens and dozens of protesters right outside were being pushed back on the streets by federal law enforcement firing what appeared to be tear gas.

Similar reports of police using tear gas against protesters have emerged across the United States over the past several days: San Diego, Los Angeles, Detroit, Las Vegas, Orlando. A reporter for the Los Angeles Times in Minneapolis posted a video, her eyes red and raw, describing how Minnesota State Police had blasted her and other journalists at point-blank range with tear gas.

In the United States, what we call “tear gas” is often CS gas, a chemical compound credited to two American scientists, Ben Corson and Roger Stoughton, who discovered it in 1928. (The C and S in “CS” come from the first initial of each man’s last name.) But its use predates that, to the battlefields of World War I — from where it migrated not long after to America’s police forces. And there it has stayed, ever since.

Park police officers are seen in a cloud of tear gas outside the White House on May 30.
Jose Luis Magana/AFP via Getty Images

Mostly because it was ruthlessly effective. It dispersed crowds and could turn a “protest into a screaming mob,” Anna Feigenbaum, an associate professor at Bournemouth University in the United Kingdom, told me.

“Because it doesn’t normally leave blood, there’s no trace,” said Feigenbaum, who is the author of the book Tear Gas: From the Battlefields of World War I to the Streets of Today.

Indeed, tear gas is deemed a “riot control agent,” which exempts it from chemical weapons protocols — meaning it can still be used on a city street by domestic police forces, but not by soldiers in a war zone. It is considered a “less lethal” weapon, meaning it’s not intended to be fatal, but it can, and often does, inflict injury, though how severe often depends on how it’s used, and when, and where.

It has become part of the landscape of protests worldwide from the Arab Spring to Hong Kong. So has its aftermath: crowds fleeing slow-moving clouds, the coughing, the choking, the water bottles dumped in stinging eyes. And as unrest engulfs the United States, the scene is repeating itself, again and again.

I spoke with Feigenbaum to better understand the history of tear gas and how it became a tool for police, past and present.

Our conversation, edited for length and clarity, is below.

Jen Kirby

When do we see the first instance of what we would consider “tear gas”?

Anna Feigenbaum

The long answer, but I’ll tell you quickly, is that [researchers] think the French police were experimenting with it before World War I. But then World War I is the first major deployment.

After World War I, lots of chemists created all kinds of chemical weapons, and for business reasons — as well as military prestige reasons — people that were involved in that wanted those products to continue to have a life.

So in the United States, the guy who ended up taking over the Chemical Warfare Service — which had been active during the war — went on a mission [with] powerful friends in publishing, lawyers, and PR to create a commercial market for tear gas. His name was Gen. Amos Fries.

And from 1919 until the early 1920s, they went to police departments and did displays, the way you would launch any product. They had advertisements taken out in all the places where their audience was. And so by the mid-1920s, tear gas started to be a regular thing in police arsenals. You see a lot of it being used in labor movement repression, mostly in the early ’30s.

Bullets and tear gas being used against striking workers of the Spang Chalfant Company in Ambridge, Pennsylvania, in 1934.
Underwood Archives/Getty Images

Jen Kirby

In the US, is there a first documented case of tear gas being used in a protest, or, as you mentioned, against labor unions or anything like that?

Anna Feigenbaum

I don’t know which one is the first, but the biggest that is on record is the Bonus Army March of 1932. That was a gathering of thousands of World War I veterans who had marched to Washington, DC, to claim this money they had been promised. It was during the Great Depression, so people were really broke. You see a lot of similarities to now, the kind of state that America was in.

And the military was called out against these veterans and they mass deployed tear gas. [The veterans were] all unarmed. That then both became major news, but also became part of the promotional material for how well the tear gas worked.

Jen Kirby

Was it initially marketed in the same way we see tear gas used today, for crowd-control purposes? Or did it evolve from what it was originally intended to be?

Anna Feigenbaum

I would say that its use now is exactly the same as its use then, only then they didn’t have euphemisms for it. It was just called things like “blinding, painful poison gas.” The ads would run with lines like: “Make a mob terrified and cry screaming.”

It was very much pitched openly — openly in trade magazines, not sold to the public — as being something police could use quickly, they wouldn’t need much training to use. You’d be able to win the media war because by firing the tear gas, you turn the protest into a screaming mob that, because it doesn’t normally leave blood, there’s no trace. You don’t look like the bad guy, and you just make the people look disheveled.

So all those kinds of propagandistic ways that tear gas functions — and in addition to the physical ways that it functions — were just a lot more straightforward. Whereas now, you know, normally a company wouldn’t claim something like that in any kind of public material.

Jen Kirby

And so obviously this was happening in the US, but were authorities or police around the world also adopting tear gas as a tool?

Anna Feigenbaum

I didn’t research into lots of other countries, but France and South Africa were widely using it in the 1920s as well, somewhat for obvious reasons. France had lots of colonial uprisings that it needed repressed, and South Africa, right?

So it was in European countries and European settler countries, you had the use of tear gas to quell uprisings from colonized people. In the US, it was more the kind of internal colonizing. It very much maps onto a colonial understanding of power. All of those places were using tear gas as part of their apparatus to stay in charge.

Jen Kirby

So is the substance we know as “tear gas” today the same compound as it was in the 1920s? How much has the compound actually changed?

Anna Feigenbaum

They changed them a lot. The stuff that was used in World War I is not used now. They modernized it through various things. The guys [credited for creating it], the CS guys, were scientists who made a product. They weren’t that directly involved in the kind of riot control industry, per se. And their compound didn’t actually start to get taken up until the 1950s.

The modern CS we use today is not that different from the 1950s version. Every time [the industry] makes something new, they say it’s for safety. Other times they say it’s for greater impact.

But what has really changed is the ways that tear gas is deployed. So we now have all different kinds of sprays. We’ve seen on the streets in the United States, both handheld aerosols and the bigger spray bottles that look a little bit like fire extinguishers. So that can be either an aerosol form of CS or it can be a pepper spray. They put all different kinds of chemicals in there.

A protester holds a smoke canister deployed by Detroit police on May 30.
Matthew Hatcher/Getty Images

Jen Kirby

So just to be clear, there are many things that fall under the heading of “tear gas” — like the CS, and also pepper spray?

Anna Feigenbaum

Tear gas is not really a thing. Tear gas is just the name for a bunch of different chemicals that have very, very, very slightly different effects than pepper spray.

The thing that we call pepper spray is usually either a synthetic or natural compound, but then has lots of chemicals added to it. And then there’s CS, which is the main kind of tear gas that we’ve been talking about. And then there’s CR and CN, and then there’s various other formulas that different places use.

You can have “gases” in different forms. It can be liquid, it can be powder. So when we see the devices that spray or shoot a substance, it could have pepper spray or a liquidized aerosol form of tear gas. Then there’s also mace, which has its own compound, but it’s also a brand name. It’s super complicated.

Jen Kirby

So when we say “tear gas,” we are not necessarily referring to one specific thing. It can be many different tools that police are using to do crowd control.

Anna Feigenbaum

Yes, yes, yes. And then the launchers, the things that are hurting people, are those big canisters that are shot from launchers that dislodge something with tear gas in it.

And so those are the things that have really been innovated in the last 20 years. We’re seeing a lot of these [canisters] that split apart into multiple pieces, or they bounce, in order to make it harder for protesters to pick them up or throw them out of the way. So those are more modern inventions. They have to do with the dispersal technology, not the formula.

Jen Kirby

So really the thing that’s changed is how tear gas is actually deployed by police forces and authorities worldwide?

Anna Feigenbaum

It’s those innovations — like, yes, they tweak the formula — but the thing that has made a difference from the perspective of the person being tear-gassed are these different ways of deploying it.

Because if you’re making ever faster, ever more powerful multi-launchers that can fire canisters that split into multiple pieces at people, you’re much more likely increasing harm, right? You’re increasing [law enforcement’s] capacity to control that space, from a freedom-of-assembly perspective.

And then things like pepper balls, those little balls that are being rapidly fired like machine guns, they look like paintball guns. Some cities use a lot of those. That’s a more modern technology that changes the way that you experience being pepper-sprayed or being tear-gassed.

Jen Kirby

And how do these new methods of delivery change how people experience being tear-gassed?

Anna Feigenbaum

It would depend. The concern people have with the ones that split apart is that you have less accuracy in where you’re firing it. The same with the bouncing ones. If it’s bouncing around, it’s going to be less accurate, where it’s firing.

You’re supposed to not fire them at people, you’re supposed to fire them well in front of people, giving everyone a clear amount of space to disperse after a very clear verbal warning.

Very little of the way we’re seeing tear gas being used follows any of the protocol which underlie the fact that it’s legal. In the kinds of situations where we’re seeing tear gas used in the US right now, the thing that makes it more dangerous is the amount, and how trapped people are in a space.

Jen Kirby

Can you talk about the legality? As I understand it, there are some international protocols, including from the United Nations, on the use of tear gas, or riot control agents. But what are the actual underpinnings of the legality, and is it just international protocols or are there federal or state laws, too?

Anna Feigenbaum

Internationally, the main regulator would be the OPCW (Organization for the Prohibition of Chemical Weapons), and that’s the one where you have that exception clause that says that things that are “riot control agents” are exempt from the Chemical Weapons Convention, which is what outlaws other kinds of chemical war.

And then a [police] precinct could have its own policy or rule. But there’s no legally enforced, wide-scale regulation.

What most people in the policy world who are advocating for reform around tear gas want is clear definitions of what kinds of chemicals can be put in the formulas and of what kinds of launchers can be used. Then on the legal side of that, a better way of enforcing misuse.

For example, if you’ve seen the video [editor’s note: the video appears to show police firing tear gas at protesters near Philadelphia on June 1] where protesters are fired at and they’re all trying to run up this hill, on the side of a road, and they have literally nowhere to go, and they’re just being pummeled.

That would be one of the most dangerous ways of using tear gas. That would be completely against military and police training. That’s the kind of thing that the UN use-of-force laws would be wanting to not allow.

Philadelphia police use tear gas on protesters after a march through Center City on June 1.
Mark Makela/Getty Images

Jen Kirby

So I’m understanding now that there’s nothing really enforceable, but if I’m a police officer who wants to use this for crowd control, what are the steps, if you’re going use it “appropriately”?

Anna Feigenbaum

Again, protocols will change in different places, but first of all, you would have to be under some kind of threat that you couldn’t contain, or couldn’t change without the use of a less lethal weapon. So that’s number one.

That’s in the UN’s basic principles for the use of force. If you were going to use it because you deemed there was danger, or you felt threatened — which is usually the excuse that US police use — then you would have to give the verbal warning.

You would wait a suitable amount of time for people to actually leave, and then you would fire the tear gas on the ground, a good distance in front of where people are, so that you didn’t run the risk of either hitting them with a canister or a grenade, or getting the gas too close to them so that they might have too much of it, too big of a dose.

And the wind would need to be in the right direction. You would need to have multiple clear exit paths for people to get away from it. And anyone who was injured, you would go and care for [them], rather than arresting them.

Jen Kirby

Do you think some of the anger around the use of tear gas is in part because these protocols are not being followed? I don’t know what you’ve seen in your research, but when we see tear gas being used — as in these recent anti-police brutality protests in the US, but also in the pro-democracy protests in Hong Kong this summer — are we just seeing bad examples? Or is it really just a free-for-all?

Anna Feigenbaum

Potentially both right now in the US. It’s hard for me to judge that because I’m not in the US, so I’m not even getting that trickle of media that you get when you’re there. I’m getting just whatever people retweet on Twitter, or whatever’s picked up by the major press.

I would say I, personally, have not seen any videos of appropriate use — which doesn’t mean they are not somewhere, people following protocol.

And actually, in the early days of the Hong Kong protests, the police were completely following protocol. It was only as the protests escalated over time that you started to see the Hong Kong police get much more violent.

So there are certainly instances, like in the early, early days of Hong Kong, where the police were following protocol to the book. There’s also all this tactical formation [police are] supposed to do — so there’s one guy that’s in charge of other guys, and that guy says fire and then that’s when you fire.

There’s all of this sort of military precision that’s supposed to happen. It’s not supposed to be just random people shooting constantly. I would say how we saw the use in Turkey [in anti-Erdogan protests 2013] and in Egypt [in Tahrir Square during the 2011 Arab Spring] is more like what we’re seeing now in the US, just kind of free-for-all.

Jen Kirby

What are the public health consequences of deploying tear gas for protests?

Anna Feigenbaum

I think that it’s really important to look at it from a public health perspective. It’s still questionable what kinds of respiratory damage tear gas does. We don’t really know what its impacts are in terms of different kinds of asthma and lung disease.

What we do know is that for people who have any kind of preconditions, it’s incredibly dangerous for them to be in spaces that are tear-gassed. For anyone who’s very young or very old, it has increased dangers.

So if we think of this as an atmospheric weapon — a weapon that takes over the space of the air — then anybody who is in that space becomes vulnerable to its effects. And so in the same way that we are shielding people who are vulnerable from Covid-19 — you have to think about it in a similar way. You’re more likely to be badly impacted by tear gas if you fall into the higher-risk categories.

A protestor douses her face with milk after being exposed to tear gas fired by police in St. Paul on May 28.
John Minchillo/AP

In that way, it can very much be analyzed in terms of public health framework. And so you might say it’s discriminatory — of who’s allowed to freely assemble — because it makes certain bodies much, much more vulnerable and therefore denies them that right of participation. I mean, I think you can argue that tear gas, in and of itself, denies people the right to protest and publicly assemble.

Then in terms of its environmental, architectural damage, it’s a toxic waste. It’s a hazardous material. We are firing it into our parks, into water supplies sometimes. If people have it on them and bring it home, if it goes into any kind of windows that are open, if it goes in people’s homes, all of that. You’re basically just spreading a toxic waste material into public and private spaces.

If you look at the police protocol for how to decontaminate from pepper spray or tear gas exposure, it’s incredibly meticulous. It refers to it as being highly dangerous. And yet, when it’s used against the public, no such provision is given for cleaning any of these spaces or decontaminating any of these spaces.

Jen Kirby

Given that, has there been any kind of real movement or push to rethink how tear gas is being used?

Anna Feigenbaum

From an activist perspective, after Occupy, the War Resisters League had a Facing Tear Gas campaign. And that, I think, was the first concerted effort in the US to call out the companies or the manufacturers, and so that got on the map that you could have corporate activism against manufacturers of tear gas.

We really saw that then come back with the Warren Kanders/Whitney Museum thing that happened with Decolonize This Place. Kanders, who runs the Safariland Group, which was the tear gas used against the migrant caravan [along the US southern border], that ended up sparking this movement to try to get him off of the board of the Whitney. And then all these artists got involved, and he had to resign.

So that is a good example of using corporate activism that had its foundation in the post-Occupy [movement] — and, I mean, the actual organizers are kind of the same people. There was a trajectory there of thinking about how to intervene through that route.

And after Ferguson, there was a lawsuit where protesters won. But what they won was the thing that’s supposed to be protocol anyway: They won the police department agreeing to the fact that they should give a verbal warning and let people leave a space. It was a kind of one step forward, two steps back.

Jen Kirby

It seems like most of that has been activist-led. Have there been any police departments or authorities who’ve had an internal reckoning about the use of tear gas?

Anna Feigenbaum

Only in the offhand that, you know, occasionally someone who’s a police trainer will get in touch with me and be like, “I use a different kind of training in mine.”

The other thing, and I don’t know enough about the internal operations of US police departments, but the tactical squad that gets called out for riot control is not the whole police force.

So I would imagine that, internally to a police department, you have some issues between who’s on the tactical squad and why, and people who are beat cops, desk cops, or whatever. Police departments also have all of their own complicated hierarchies and systems going on, right?

Jen Kirby

What strikes me most is that a police officer can use tear gas, but it can’t be used in warfare. Can you explain this disconnect?

Anna Feigenbaum

Things that are classified as riot control agents are exempt from the ban on using chemical weapons and there’s also part of that exemption, which is about defensive versus offensive force. The idea is that if tear gas is used in war, it would be a part of an offensive [operation], whereas when the police use tear gas, it is defensive.

Jen Kirby

Obviously the protests are complicated, and I’m not unsympathetic to the fact that there may be situations where a police officer might feel they need more tools to control a crowd. So is there a better way than tear gas? Does something exist that might do the same job, but also be more protective of the public?

Anna Feigenbaum

The situation that we’re in now is a result of so many failures of democracy. The solution for this is real democracy, is listening to people, is taking people seriously, treating people as humans. By the time that you need to be deploying riot control squads against your own people on this scale, you’ve had a massive democratic failure.

So I think the problem here, and in many of these instances, like Ferguson, where we see this kind of [police] deployment and deployment of the National Guard, is that there’s been a massive failure in the very meaning of democracy, of people participating in their own governing and people participating in the society that they live in.

The solution to that is not better police equipment or more police. It is less police equipment, less police, and more democracy, more ways of guaranteeing people’s basic rights and freedoms.

Jen Kirby

To that point, is there something about the use of tear gas in this moment in time that strikes you as particularly unique? Or is this just a reprise of history?

Anna Feigenbaum

I would say that it’s a reprise of history, but it’s a reprise of white supremacist moments in history.

This kind of unashamed, full-force, no-apology use of the police to protect a minority elite in power with no concern for the cost of doing that, has been something that — as I’ve watched the news — is eerily reminiscent of a few previous moments in history where we had white supremacists in positions of power that deployed the police en masse.

Police officers push back demonstrators with tear gas next to St. John’s Episcopal Church outside of the White House on June 1.
Jose Luis Magana/AFP via Getty Images

Jen Kirby

My last question is a practical one: If people are concerned about the use of tear gas, where should they start? How should people advocate, and is there a worthwhile policy change to pursue?

Anna Feigenbaum

I think the current move to defund police departments, and to force police departments to be much more transparent about where their budgets are going.

In most police departments, you can’t line-item how much riot control equipment is being bought, or armor or training. I think, first, that kind of data transparency and defunding that kind of aspect of policing. I think the movement that is happening right now is really important, that we need to stop talking about reform and start talking about defunding.

And, you know, I think, in a very practical way, funding your street medics, making sure that street medics are equipped and are safe.

Then, as we saw with Kanders and the Whitney, I think corporate-based activism, more outing of these manufacturers, more outing of who they are and how they profit off these moments.

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