Tear gas 101: what it does and why it’s deadly

As protestors across the US find themselves smothered by an intoxicating smog that causes tearing, burning and trouble breathing, four experts outline the dangers of so-called “non-lethal” weapons that are banned in warfare, yet remain legal for domestic matters of law enforcement.

As protests swept through America in outrage at the death of George Floyd – an unarmed black man, killed in police custody – crowds across the country found themselves smothered by an intoxicating smog: tear gas. 

Used to control protesters in multiple cities in recent days, reports of its deployment have run from New York to Minneapolis, Philadelphia and Washington DC. Today, it was reported that a 22-year old protestor named Sarah Grossman died after attending a demonstration in Columbus, Ohio, at which she was tear-gassed and pepper-sprayed by police. The young woman’s cause of death remains under investigation.

Tear gas is a fine powdery solid – confusingly, not a gas – which can be released via grenade, aerosol, spray, canister or pellet, and most commonly comprises one of two compounds: chlorobenzylidenemalononitrile (CS) or chloroacetophenone (CN).

Pepper spray – oleoresin capsicum (OC) – is also often considered a form of the gas, although made from an organic resin from chilli peppers. 

Designed as a chemical irritant, tear gas can cause all manner of immediate health problems, from tearing and burning, to trouble breathing. 

The Geneva Convention of 1925 classified it as a chemical weapon, and its use was prohibited in warfare. The International Chemical Weapons Convention, which came into force in 1997, banned the use of riot control agents (RCAs), of which tear gas is one, in warfare as well. Yet these agents – known as non-lethal weapons” – were not prohibited for domestic purposes of law enforcement, including riot control.

And the question many are now asking is: why? 

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A cohesive large crowd is almost like this one organism that can move and can be very dangerous,” says Brian Higgins. The use of [tear] gas would be used to disperse a violent, unruly crowd.”

Higgins is a crowd control expert who teaches at the John Jay College of Criminal Justice. He also worked as a New Jersey police officer for over twenty years and as a police chief for four. There’s a big difference between crowd management and crowd control,” he continues. When you see police using shields and batons and gas, you’re now in crowd control. The idea is to manage a crowd before it gets to that point.”

He explains that policing in the States is about working through a model called the use-of-force continuum”. It starts when officers arrive, identify themselves, and issue an instruction – if ignored, they move up the continuum. In the US, the use of force is determined by the threat and only the appropriate amount of force can be used to address the level of threat. And at some point, you would get to pepper spray or some other type of irritant such as CS or CN gas,” he says.

He emphasises, however, that tear gas is designed for use only in situations where a crowd is deemed to have become dangerous. The use of gas and other less-than-lethal’ items are a better alternative to the use of deadly force,” he says. 

But adds, if somebody gets too much [gas], it could cause some serious health issues.”

Protocols for the police use of force are meant to regulate how tear gas and other riot control devices are used against civilians to help keep everyone as safe as possible,” says Dr Anna Feigenbaum, author of Tear Gas: From the Battlefields of World War I to the Streets of Today.

However, there is a lot of footage coming through that does not appear to follow these protocols. For example, tear gas canisters are being fired at close range, directly at protesters and in enclosed spaces.”

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Tear gases are designed to attack the senses simultaneously, intentionally producing both physical and psychological trauma,” Dr Feigenbaum explains. In medical terms, [it] operates as an irritant on multiple sites of the body at once, primarily affecting mucous membranes and respiratory system.”

She details a number of possible reactions. An extensive list, it includes excessive tearing, blurred vision, burning of the nostrils and mouth, skin burns, difficulty swallowing, chest tightness, coughing, wheezing, shortness of breath, rashes, nausea and vomiting – amongst others. 

In most cases, the response is brief. As Dr Alistair Hay – emeritus professor of environmental toxicology at the University of Leeds – describes, RCAs generally have a temporary effect”, and symptoms wear off after some 20 minutes to an hour”.

But this isn’t always the case. Dr Rohini Haar, an emergency physician and medical expert at Physicians for Human Rights, says there is evidence that exposure can cause more lasting damage. Scientific reviews on long term effects of these chemical irritants have documented that they can cause permanent disabilities and deaths,” she says.

A 2016 study, conducted by professor Sven-Eric Jordt et al, looking at existing data on the health effects of tear gas exposure, noted, numerous case reports of injuries and fatalities associated with exposure to high concentrations of tear gas or exposure in enclosed spaces or for extended periods of time”, and went on to state deaths and respiratory tract injuries had been recorded following tear gas use in prisons.

It also highlighted, however, a dearth of epidemiological research into what people might experience following authentic instances of tear gas exposure – i.e. those not carried out in controlled environments – which it noted was in part owing to the difficulty attached to conducting analysis in real-world conditions” – in other words, in the midst of a protest.

Worryingly, it added: The effects of RCA exposure among sensitive populations and among those with underlying health conditions are one such area where the level of risk is unclear.”

Beyond the physical, there are also the psychological effects to consider. As Dr Feigenbaum explains, Exposure to tear gas, especially if deployed excessively and repetitively, has been shown to contribute to PTSD [post traumatic stress disorder] and have negative mental health impacts.”

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There is another factor currently worsening the danger that tear gas use may pose and that is, of course, the ongoing Covid-19 pandemic. While as yet there is no research to turn to, experts say deployment of the gas in today’s climate could impact transmission of the virus, and may exacerbate symptoms as well. Dr Peter Chin-Hong, professor of medicine and an infectious disease specialist at University of California, San Francisco, is one such expert.

How does one who is negative for Covid-19 potentially increase risk of Covid-19 acquisition? There are two [ways],” he says.

[Tear gas] is an irritant, so you’re rubbing your eyes, your nose, your mouth, vigorously… And you’re in the field so you haven’t really washed your hands or been able to use hand sanitiser,” he explains. That’s a really efficient way of transferring whatever was on your hands into your mouth or nose.”

The second way – which he notes has biologic plausibility” but is less likely to lead to cases of Covid-19 transmission – is owing to the fact irritants like tear gas cause inflammation which can decimate some of the body’s natural lines of defence. These might include the mucosa of the nose and mouth, nose hairs, and cilia in the lungs that beat rhythmically to keep things out”. When you irritate that with a chemical burn,” he says, that line of defence is gone.”

As to whether tear gas would exacerbate the symptoms of someone already carrying the virus, Dr Chin-Hong is resolute. Totally,” he responds. Because tear gas is made to stimulate people to cough. If you were Covid-19, you would be in paradise because coughing is the way that you were designed to be transmitted.”

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There are other risks attached to tear gas deployment, beyond just the substance itself. Dr Rohini Haar points out that the devices used to contain the gas become dangerous and potentially lethal when launched. 

Canisters have caused traumatic injuries to the head, neck, and upper chest, as well as to the arms and legs,” she says. When fired from close range, in enclosed spaces, or areas where people cannot leave, they can dramatically worsen injuries and risk of death.” 

Other threats to health and safety may emerge on account of what these irritants are designed to provoke: flight. One particular concern of mine is the circumstances in which riot control agents are used,” Dr Alistair Hay says. 

Too often they have been used in confined spaces and cause panic. This may result in people stampeding to get away, and in some countries, many have died because they were trampled.”

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So how have we ended up here – a place where a method of controlling a crowd has the potential to do more harm than good? 

Originating at the turn of the 20th century, tear gas was always designed as a form of riot control, although its inaugural use is believed to have been by the French in the Battle of the Frontiers during the First World War. World War I saw a wide-scale transfer of technologies from the military to local law enforcement, as early methods for crowd control were adapted from military practices,” explains Dr Anna Feigenbaum.

Over this period in the States, tear gas became marketed as a fast, affordable and reliable tool for law enforcement,” she continues. In advertisements, early manufacturers said it could demoralise people, destroy the mob spirit’, cause physical pain and make protesters look silly.”

After civil unrest — and its repression — in the 1950s and 1960s, riot control became an industry of its own.”

While its composition has since changed, its use as a method of law enforcement has not. 

In the UK, police officers were armed with tear gas in the mid 1960s, and it was used in Northern Ireland during the Troubles the following decade. The first instance of its deployment in Great Britain was at the riot in Toxteth, Liverpool in 1981, although it has seldom been used in such a capacity since.

That is far from the case elsewhere, and there are multiple instances in recent history where its deployment has had worrying consequences. During the Arab Spring, for instance, it was used against protestors in Cairo’s Tahir Square in 2011, with reports claiming dozens” were forced to seek medical attention as a result.

A study conducted following the use of tear gas in the Gezi Park protests in Turkey 2013 revealed that of those who undertook a psychiatric assessment afterwards, 43% met diagnostic criteria for acute stress disorder”.

And in Hong Kong, where more than 12,000 rounds of tear gas were fired last year during anti-government protests, there have been reports of PTSD experienced by those exposed. 

These examples present a fragment of a far bigger picture. More research is needed to fully investigate how tear gas impacts physical and psychological health when deployed in a crowd control” situation.

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Tear gas is just one of the weapons police can reach for in an attempt to pull back control. In the States, water cannons may be utilised – as they were during a protest in North Dakota in 2016 – and sound cannons too, known as Long Range Acoustic Devices. But these also carry risks. When the latter was deployed at a Black Lives Matter protest in Manhattan, 2014, for instance, it resulted in a lawsuit after six people came forward with subsequent health problems, one of which was a hearing complaint.

As has been widely reported in recent days, police can also fire rubber bullets. There is a place for rubber bullets’,” says Brian Higgins, but to indiscriminately fire them in a crowd is not the proper use.”

Honestly, rubber bullets’ is a misnomer…” he continues. They go from very small bullets fired out of a rifle or a shotgun, up to a 40mm launcher [where] the bullets are more foam, like a dense foam.”

He adds: If you think you’re going to fire a rubber bullet, you would think, All right, that almost sounds light-hearted’. But people still die as a result of being shot with these things.”

In Higgins’ view, the most effective way to manage a crowd comes down to doing your homework before the crowd assembles” and knowing who is going to be a part of it. But it’s also – most importantly – about building good relationships between the police and the community.

Crowd-control weapons should be an absolute last resort,” Dr Rohini Haar says. Only used when dealing with genuine and imminent threats to the safety of those present, and after all other means have been exhausted.” 


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