![Exploded tear gas can on the fly](https://upload.wikimedia.org/wikipedia/commons/7/74/Exploded_tear_gas_can_on_the_fly.jpg)
Tear gas, also known as a lachrymator agent or lachrymator (), sometimes colloquially known as "mace" after the
early commercial aerosol, is a
chemical weapon
A chemical weapon (CW) is a specialized munition that uses chemicals formulated to inflict death or harm on humans. According to the Organisation for the Prohibition of Chemical Weapons (OPCW), this can be any chemical compound intended as a ...
that stimulates the nerves of the
lacrimal gland
The lacrimal glands are paired exocrine glands, one for each eye, found in most terrestrial vertebrates and some marine mammals, that secrete the aqueous layer of the tear film. In humans, they are situated in the upper lateral region of each or ...
in the eye to produce tears. In addition, it can cause severe eye and respiratory pain, skin irritation, bleeding, and blindness. Common lachrymators both currently and formerly used as tear gas include
pepper spray
Pepper spray, oleoresin capsicum spray, OC spray, capsaicin spray, or capsicum spray is a lachrymatory agent (a compound that irritates the eyes to cause a burning sensation, pain, and temporary blindness) used in policing, riot control, cr ...
(OC gas),
PAVA spray
PAVA spray is an incapacitant spray similar to pepper spray. It is dispensed from a handheld canister, in a liquid stream. It contains a 0.3% solution of pelargonic acid vanillylamide (PAVA), also called nonivamide, a synthetic capsaicinoid (anal ...
(
nonivamide
Nonivamide, also called pelargonic acid vanillylamide or PAVA, is an organic compound and a capsaicinoid. It is an amide of pelargonic acid (n-nonanoic acid) and vanillyl amine. It is present in chili peppers, but is commonly manufactured synt ...
),
CS gas
The compound 2-chlorobenzalmalononitrile (also called ''o''-chlorobenzylidene malononitrile; chemical formula: C10H5ClN2), a cyanocarbon, is the defining component of tear gas commonly referred to as CS gas, which is used as a riot control agent ...
,
CR gas
CR gas or dibenzoxazepine (chemical name dibenz 'b'',''f''1,4]oxazepine, is an incapacitating agent and a lachrymatory agent. CR was developed by the British Ministry of Defence as a riot control agent in the late 1950s and early 1960s. A report ...
,
CN gas
Phenacyl chloride, also commonly known as chloroacetophenone, is a substituted acetophenone. It is a useful building block in organic chemistry. Apart from that, it has been historically used as a riot control agent, where it is designated CN. It ...
(phenacyl chloride),
bromoacetone
Bromoacetone is an organic compound with the formula . It is a colorless liquid although impure samples appear yellow or even brown. It is a lachrymatory agent and a precursor to other organic compounds.
Occurrence in nature
Bromoacetone is pr ...
,
xylyl bromide
Xylyl bromide, also known as methylbenzyl bromide or T-stoff ('substance-T'), is any member or a mixture of organic chemical compounds with the molecular formula C6 H4(CH3)(CH2 Br). The mixture was formerly used as a tear gas and has an odor r ...
and
Mace (a branded mixture).
While lachrymatory agents are commonly deployed for
riot control
Riot control measures are used by law enforcement, military, paramilitary or security forces to control, disperse, and arrest people who are involved in a riot, unlawful demonstration or unlawful protest.
If a riot is spontaneous and irration ...
by law enforcement and military personnel, its use in warfare is prohibited by various international treaties.
[E.g. the ]Geneva Protocol
The Protocol for the Prohibition of the Use in War of Asphyxiating, Poisonous or other Gases, and of Bacteriological Methods of Warfare, usually called the Geneva Protocol, is a treaty prohibiting the use of chemical and biological weapons in ...
of 1925 prohibited the use of "asphyxiating gas, or any other kind of gas, liquids, substances or similar materials". During
World War I
World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, the United States, and the Ottoman Empire, with fightin ...
, increasingly toxic and deadly lachrymatory agents were used.
The short and long-term effects of tear gas are not well studied. The published peer-reviewed literature consists of lower quality evidence that does not establish causality. More rigorous research is needed.
Exposure to tear gas agents may produce numerous short-term and long-term health effects, including development of respiratory illnesses, severe eye injuries and diseases (such as traumatic optic neuropathy, keratitis, glaucoma, and cataracts), dermatitis, damage of cardiovascular and gastrointestinal systems, and death, especially in cases with exposure to high concentrations of tear gas or application of the tear gases in enclosed spaces.
Effects
Tear gas generally consists of
aerosol
An aerosol is a suspension (chemistry), suspension of fine solid particles or liquid Drop (liquid), droplets in air or another gas. Aerosols can be natural or Human impact on the environment, anthropogenic. Examples of natural aerosols are fog o ...
ized solid or liquid compounds (
bromoacetone
Bromoacetone is an organic compound with the formula . It is a colorless liquid although impure samples appear yellow or even brown. It is a lachrymatory agent and a precursor to other organic compounds.
Occurrence in nature
Bromoacetone is pr ...
or
xylyl bromide
Xylyl bromide, also known as methylbenzyl bromide or T-stoff ('substance-T'), is any member or a mixture of organic chemical compounds with the molecular formula C6 H4(CH3)(CH2 Br). The mixture was formerly used as a tear gas and has an odor r ...
), not gas.
Tear gas works by irritating mucous membranes in the eyes, nose, mouth and lungs. It causes crying, sneezing, coughing, difficulty breathing, pain in the eyes, and temporary blindness. With
CS gas
The compound 2-chlorobenzalmalononitrile (also called ''o''-chlorobenzylidene malononitrile; chemical formula: C10H5ClN2), a cyanocarbon, is the defining component of tear gas commonly referred to as CS gas, which is used as a riot control agent ...
, symptoms of irritation typically appear after 20 to 60 seconds of exposure
and commonly resolve within 30 minutes of leaving (or being removed from) the area.
Risks
As with all
non-lethal or less-lethal weapons, there is a risk of serious permanent injury or death when tear gas is used.
This includes risks from being hit by tear gas cartridges that may cause severe bruising, loss of eyesight, or skull fracture, resulting in immediate death.
A case of serious vascular injury from tear gas shells has also been reported from Iran, with high rates of associated nerve injury (44%) and amputation (17%),
as well as instances of head injuries in young people.
Novel findings suggest that menstrual changes are one of the most commonly reported health issues in women.
While the medical consequences of the gases themselves are typically limited to minor
skin inflammation, delayed
complications are also possible. People with pre-existing
respiratory conditions such as
asthma
Asthma is a long-term inflammatory disease of the airways of the lungs. It is characterized by variable and recurring symptoms, reversible airflow obstruction, and easily triggered bronchospasms. Symptoms include episodes of wheezing, cou ...
are particularly at risk. They are likely to need medical attention
and may sometimes require
hospitalization
A hospital is a health care institution providing patient treatment with specialized health science and auxiliary healthcare staff and medical equipment. The best-known type of hospital is the general hospital, which typically has an emergency ...
or even
ventilation support.
Skin exposure to
CS may cause
chemical burn
A chemical burn occurs when living tissue is exposed to a corrosive substance (such as a strong acid, base or oxidizer) or a cytotoxic agent (such as mustard gas, lewisite or arsine). Chemical burns follow standard burn classification and may ca ...
s
or induce
allergic contact dermatitis
Allergic contact dermatitis (ACD) is a form of contact dermatitis that is the manifestation of an allergic response caused by contact with a substance; the other type being irritant contact dermatitis (ICD).
Although less common than ICD, ACD is ...
.
When people are hit at close range or are severely exposed,
eye injuries
Eyes are organs of the visual system. They provide living organisms with vision, the ability to receive and process visual detail, as well as enabling several photo response functions that are independent of vision. Eyes detect light and conv ...
involving scarring of the
cornea
The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Along with the anterior chamber and lens, the cornea refracts light, accounting for approximately two-thirds of the eye's total optical power ...
can lead to a permanent loss in
visual acuity
Visual acuity (VA) commonly refers to the clarity of vision, but technically rates an examinee's ability to recognize small details with precision. Visual acuity is dependent on optical and neural factors, i.e. (1) the sharpness of the retinal ...
.
Frequent or high levels of exposure carry increased risks of respiratory illness.
In the
2019–20 Chilean protests various people
have had complete and permanent loss of vision in one or both eyes as result of the impact of tear gas grenades.
The majority (2116; 93.8%) of protestors who reported exposure to tear gas during the 2020 protests in Portland, Oregon (USA) reported physical (2114; 93.7%) or psychological (1635; 72.4%) health issues experienced immediately after (2105; 93.3%) or days following (1944; 86.1%) the exposure. The majority (1233; 54.6%) of respondents who reported exposure to tear gas during the 2020 protests in Portland, Oregon (USA) have also reported receiving or planning to seek medical or mental healthcare for their tear gas-related health issues.
It has been shown that health issues associated with the exposure to tear gas are often require medical attention.
Site of action
TRPA1
Transient receptor potential cation channel, subfamily A, member 1, also known as transient receptor potential ankyrin 1, TRPA1, or The Wasabi Receptor, is a protein that in humans is encoded by the ''TRPA1'' (and in mice and rats by the ''Trpa1' ...
ion channels expressed on nociceptors have been implicated as the site of action for
CS gas
The compound 2-chlorobenzalmalononitrile (also called ''o''-chlorobenzylidene malononitrile; chemical formula: C10H5ClN2), a cyanocarbon, is the defining component of tear gas commonly referred to as CS gas, which is used as a riot control agent ...
,
CR gas
CR gas or dibenzoxazepine (chemical name dibenz 'b'',''f''1,4]oxazepine, is an incapacitating agent and a lachrymatory agent. CR was developed by the British Ministry of Defence as a riot control agent in the late 1950s and early 1960s. A report ...
,
CN gas
Phenacyl chloride, also commonly known as chloroacetophenone, is a substituted acetophenone. It is a useful building block in organic chemistry. Apart from that, it has been historically used as a riot control agent, where it is designated CN. It ...
(phenacyl chloride) and
bromoacetone
Bromoacetone is an organic compound with the formula . It is a colorless liquid although impure samples appear yellow or even brown. It is a lachrymatory agent and a precursor to other organic compounds.
Occurrence in nature
Bromoacetone is pr ...
in rodent models.
Use
Warfare
During
World War I
World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, the United States, and the Ottoman Empire, with fightin ...
, various forms of tear gas were used in combat and tear gas was the most common form of chemical weapon used. None of the belligerents believed that the use of irritant gases violated the
Hague Conventions of 1899 and 1907, Hague Convention of 1899 which prohibited the use of "poison or poisoned weapons" in warfare. Use of chemical weapons escalated during the war to lethal gases, after 1914 (during which only tear gas was used).
The US
Chemical Warfare Service
The Chemical Corps is the branch of the United States Army tasked with defending against chemical, biological, radiological, and nuclear (CBRN) weapons. The Chemical Warfare Service was established on 28 June 1918, combining activities that un ...
developed tear gas grenades for use in riot control in 1919.
Use of tear gas in warfare, as with all other
chemical weapon
A chemical weapon (CW) is a specialized munition that uses chemicals formulated to inflict death or harm on humans. According to the Organisation for the Prohibition of Chemical Weapons (OPCW), this can be any chemical compound intended as a ...
s, was prohibited by the
Geneva Protocol
The Protocol for the Prohibition of the Use in War of Asphyxiating, Poisonous or other Gases, and of Bacteriological Methods of Warfare, usually called the Geneva Protocol, is a treaty prohibiting the use of chemical and biological weapons in ...
of 1925: it prohibited the use of "asphyxiating gas, or any other kind of gas, liquids, substances or similar materials", a treaty that most states have signed. Police and civilian self-defense use is not banned in the same manner.
Tear gas was used in combat by Italy in the
Second Italo-Ethiopian War
The Second Italo-Ethiopian War, also referred to as the Second Italo-Abyssinian War, was a war of aggression which was fought between Italy and Ethiopia from October 1935 to February 1937. In Ethiopia it is often referred to simply as the Itali ...
, by Japan in the
Second Sino-Japanese War
The Second Sino-Japanese War (1937–1945) or War of Resistance (Chinese term) was a military conflict that was primarily waged between the Republic of China and the Empire of Japan. The war made up the Chinese theater of the wider Pacific Th ...
, by Spain in the
Rif War
The Rif War () was an armed conflict fought from 1921 to 1926 between Spain (joined by History of France, France in 1924) and the Berbers, Berber tribes of the mountainous Rif region of northern Morocco.
Led by Abd el-Krim, the Riffians at ...
and by the United States in the
Vietnam War
The Vietnam War (also known by #Names, other names) was a conflict in Vietnam, Laos, and Cambodia from 1 November 1955 to the fall of Saigon on 30 April 1975. It was the second of the Indochina Wars and was officially fought between North Vie ...
, and the
Israel-Palestine conflict.
Tear gas exposure is an element of military training programs, typically as a means of improving trainees' tolerance to tear gas and encouraging confidence in the ability of their issued protective equipment to prevent chemical weapons exposure.
Riot control
Certain lachrymatory agents, most notably tear gas, are often used by police to force compliance.
In some countries (e.g., Finland, Australia, and United States), another common substance is
mace. The self-defense weapon form of mace is based on
pepper spray
Pepper spray, oleoresin capsicum spray, OC spray, capsaicin spray, or capsicum spray is a lachrymatory agent (a compound that irritates the eyes to cause a burning sensation, pain, and temporary blindness) used in policing, riot control, cr ...
which comes in small spray cans. Versions including CS are manufactured for police use.
Xylyl bromide, CN and CS are the oldest of these agents. CS is the most widely used. CN has the most recorded toxicity.
Typical manufacturer warnings on tear gas cartridges state "Danger: Do not fire directly at person(s). Severe injury or death may result."
Tear gas guns do not have a manual setting to adjust the range of fire. The only way to adjust the projectile's range is to aim towards the ground at the correct angle. Incorrect aim will send the capsules away from the targets, causing risk for non-targets instead.
Counter-measures
A variety of protective equipment may be used, including
gas mask
A gas mask is a mask used to protect the wearer from inhaling airborne pollutants and toxic gases. The mask forms a sealed cover over the nose and mouth, but may also cover the eyes and other vulnerable soft tissues of the face. Most gas mask ...
s and
respirator
A respirator is a device designed to protect the wearer from inhaling hazardous atmospheres including fumes, vapours, gases and particulate matter such as dusts and airborne pathogens such as viruses. There are two main categories of respi ...
s. In
riot control
Riot control measures are used by law enforcement, military, paramilitary or security forces to control, disperse, and arrest people who are involved in a riot, unlawful demonstration or unlawful protest.
If a riot is spontaneous and irration ...
situations, protesters sometimes use equipment (aside from simple rags or clothing over the mouth) such as
swimming goggles
Goggles, or safety glasses, are forms of protective eyewear that usually enclose or protect the area surrounding the eye in order to prevent particulates, water or chemicals from striking the eyes. They are used in chemistry laboratories and ...
and adapted water bottles, as well as covering as much skin as possible.
Activists in United States, the Czech Republic, Venezuela and Turkey have reported using
antacid
An antacid is a substance which neutralizes stomach acidity and is used to relieve heartburn, indigestion or an upset stomach. Some antacids have been used in the treatment of constipation and diarrhea. Marketed antacids contain salts of alumi ...
solutions such as
Maalox
Maalox is a brand of antacid owned by Sanofi. Their main product is a flavored liquid containing a suspension of aluminum hydroxide and magnesium hydroxide, which act to neutralize or reduce stomach acid, for the purpose of relieving the symptom ...
diluted with water to repel effects of tear gas attacks, with Venezuelan chemist
Mónica Kräuter recommending the usage of diluted antacids as well as
baking soda
Sodium bicarbonate (IUPAC name: sodium hydrogencarbonate), commonly known as baking soda or bicarbonate of soda, is a chemical compound with the formula NaHCO3. It is a salt composed of a sodium cation ( Na+) and a bicarbonate anion ( HCO3−) ...
.
There have also been reports of these antacids being helpful for tear gas,
and for capsaicin-induced skin pain.
During the
2019 Hong Kong protests, frontline protesters became adept at extinguishing tear gas: they formed special teams that spring into action as soon as it is fired. These individuals generally wear protective clothing, including heat-proof gloves, or cover their arms and legs with cling film to prevent the painful skin irritation. Canisters are sometimes picked up and lobbed back at police or extinguished straight away with water, or neutralized using objects such as traffic cones. They share information about models of 3M respirator filters which have been found to be most effective against tear gas, and where those models could be purchased. Other volunteers carry saline solutions to rinse the eyes of those affected.
Similarly,
Chilean protesters of
Primera Línea
''Primera Línea'' (lit. ''First line'' or ''Frontline'') is the name for a loose collective of protesters dedicated to physically confronting Chilean riot police, that is, through acts of civil disobedience, in the context of the 2019–2022 Ch ...
have specialized individuals collecting and extinguishing the tear gas grenades. Others act as tear gas medics, while yet another group, the so-called shield-bearers, protect the protesters from the direct physical impact of the grenades.
Treatment
![Fabiola_Campillai_2021](https://upload.wikimedia.org/wikipedia/commons/0/01/Fabiola_Campillai_2021.jpg)
There is no specific antidote to common tear gases.
At the first sign of exposure or potential exposure, masks are applied when available. People are removed from the affected area when possible.
Immediate removal of contact lenses has also been recommended, as they can retain particles.
Decontamination is by physical or mechanical removal (brushing, washing, rinsing) of solid or liquid agents. Water may transiently exacerbate the pain caused by
CS gas
The compound 2-chlorobenzalmalononitrile (also called ''o''-chlorobenzylidene malononitrile; chemical formula: C10H5ClN2), a cyanocarbon, is the defining component of tear gas commonly referred to as CS gas, which is used as a riot control agent ...
and
pepper spray
Pepper spray, oleoresin capsicum spray, OC spray, capsaicin spray, or capsicum spray is a lachrymatory agent (a compound that irritates the eyes to cause a burning sensation, pain, and temporary blindness) used in policing, riot control, cr ...
but is still effective, although fat-containing oils or soaps may be more effective against pepper spray. Eyes are decontaminated by copious flushing with sterile water or saline or (with OC) open-eye exposure to wind from a fan. Referral to an ophthalmologist is needed if slit-lamp examination shows impaction of solid particles of agent.
Blowing the nose to get rid of the chemicals is recommended, as is avoiding rubbing of the eyes.
There are reports that water may increase pain from CS gas, but the balance of limited evidence currently suggests water or saline are the best options.
Some evidence suggests that
Diphoterine
Diphoterine® is a Human decontamination, decontamination solution used in first aid for the emergency treatment of Chemical hazard, chemical spills to the eyes and body.
Mechanism of action
Diphoterine® solution contains an Amphoterism, amphote ...
, a hypertonic
amphoteric
In chemistry, an amphoteric compound () is a molecule or ion that can react both as an acid and as a base. What exactly this can mean depends on which definitions of acids and bases are being used.
One type of amphoteric species are amphiproti ...
salt solution, a first aid product for chemical splashes, may help with ocular burns or chemicals in the eye.
Bathing and washing the body vigorously with soap and water can remove particles that adhere to the skin. Clothes, shoes and accessories that come into contact with vapors must be washed well since all untreated particles can remain active for up to a week.
Some advocate using fans or hair dryers to evaporate the spray, but this has not been shown to be better than washing out the eyes and it may spread contamination.
Anticholinergic
Anticholinergics (anticholinergic agents) are substances that block the action of the neurotransmitter called acetylcholine (ACh) at synapses in the central and peripheral nervous system.
These agents inhibit the parasympathetic nervous system ...
s can work like some
antihistamine
Antihistamines are drugs which treat allergic rhinitis, common cold, influenza, and other allergies. Typically, people take antihistamines as an inexpensive, generic (not patented) drug that can be bought without a prescription and provides re ...
s as they reduce lacrymation and decrease salivation, acting as an
antisialagogue, and for overall nose discomfort as they are used to treat
allergic reactions in the nose (e.g., itching, runny nose, and sneezing).
Oral analgesics may help relieve eye pain.
Most effects resulting from riot-control agents are transient and do not require treatment beyond decontamination, and most patients do not need observation beyond 4 hours. However, patients should be instructed to return if they develop effects such as
blistering
A blister is a small pocket of fluid in the upper layer of the skin caused by heat, electricity, chemicals, light, radiation, or friction
Blister(s) or Blistering may also refer to:
* Anti-torpedo bulge, also known as an anti-torpedo blister
* ...
or delayed-onset shortness of breath.
Home remedies
Vinegar,
petroleum jelly
Petroleum jelly, petrolatum, white petrolatum, soft paraffin, or multi-hydrocarbon, CAS number 8009-03-8, is a semi-solid mixture of hydrocarbons (with carbon numbers mainly higher than 25), originally promoted as a topical ointment for its h ...
, milk and lemon juice solutions have also been used by activists.
It is unclear how effective these remedies are. In particular, vinegar itself can burn the eyes and prolonged inhalation can also irritate the airways.
Though vegetable oil and vinegar have also been reported as helping relieve burning caused by pepper spray,
Kräuter suggests the usage of baking soda or toothpaste, stating that they trap the particles emanating from the gas near the airways that are more feasible to inhale.
A small trial of baby shampoo for washing out the eyes did not show any benefit.
See also
*
Law of war
The law of war is the component of international law that regulates the conditions for initiating war (''jus ad bellum'') and the conduct of warring parties (''jus in bello''). Laws of war define sovereignty and nationhood, states and territor ...
*
Baton (law enforcement)
A baton (also known as a truncheon or nightstick) is a roughly cylindrical club made of wood, rubber, plastic, or metal. It is carried as a compliance tool and defensive weapon by law-enforcement officers, correctional staff, security guards ...
*
Nerve gas
Nerve agents, sometimes also called nerve gases, are a class of organic chemicals that disrupt the mechanisms by which nerves transfer messages to organs. The disruption is caused by the blocking of acetylcholinesterase (AChE), an enzyme that ...
*
Rubber bullet
Rubber bullets (also called rubber baton rounds) are a type of baton round. Despite the name, rubber bullets typically have either a metal core with a rubber coating, or are a homogeneous admixture with rubber being a minority component. Altho ...
Notes
References
Further reading
*
* Feigenbaum, Anna, "Tear Gas Design and Dissent" in Tom Bieling (Ed.) (2019): Design (&) Activism: Perspectives on Design as Activism and Activism as Design, Milano: Mimesis, p. 97–104.
*
External links
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Articles containing video clips
Chemical safety
Chemical weapons
Lachrymatory agents
Non-lethal weapons