Tear gas
Tear gas, formally known as a lachrymator agent or lachrymator, sometimes colloquially known as mace, is a chemical weapon that causes severe eye and respiratory pain, skin irritation, bleeding, and blindness. In the eye, it stimulates the nerves of the lacrimal gland to produce tears. Common lachrymators both currently and formerly used as tear gas include pepper spray, PAVA spray, CS gas, CR gas, CN gas, bromoacetone, xylyl bromide and Mace.
While lachrymatory agents are commonly deployed for riot control by law enforcement and military personnel, its use in warfare is prohibited by various international treaties. During World War I, increasingly toxic and deadly lachrymatory agents were used.
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, 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 aerosolized solid or liquid compounds, 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, symptoms of irritation typically appear after 20 to 60 seconds of exposure and commonly resolve within 30 minutes of leaving the area.Risks
As with all non-lethal or less-lethal weapons, there is some 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 and amputation, as well as instances of head injuries in young people.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 are particularly at risk. They are likely to need medical attention and may sometimes require hospitalization or even ventilation support. Skin exposure to CS may cause chemical burns or induce allergic contact dermatitis. When people are hit at close range or are severely exposed, eye injuries involving scarring of the cornea can lead to a permanent loss in visual acuity. Frequent or high levels of exposure carry increased risks of respiratory illness.
In the 2019–20 Chilean protests various people have suffered complete and permanent loss of vision in one or both eyes as result of the impact of tear gas grenades.
Site of Action
ion channels expressed on nociceptors have been implicated as the site of action for CS gas, CR gas, CN gas and bromoacetone in rodent models.Use
Warfare
During World War I, 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 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.The US Chemical Warfare Service developed tear gas grenades for use in riot control in 1919.
Use of tear gas in warfare, as with all other chemical weapons, was prohibited by the Geneva Protocol 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.
Tear gas was used in combat by Italy in the Second Italo-Ethiopian War, by Japan in the Second Sino-Japanese War, Spain in the Rif War and by the United States in the Vietnam War.
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, another common substance is mace. The self-defense weapon form of mace is based on pepper spray 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. 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 masks and respirators. In riot control situations, protesters sometimes use equipment such as swimming goggles and adapted water bottles.Activists in United States, Czech Republic, Venezuela and Turkey have reported using antacid solutions such as Maalox 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. 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 neutralised 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 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
There is no specific antidote to common tear gases. Getting clear of gas and into fresh air is the first line of action. Removing contaminated clothing and avoiding shared use of contaminated towels could help reduce skin reactions. Immediate removal of contact lenses has also been recommended, as they can retain particles.Once a person has been exposed, there are a variety of methods to remove as much chemical as possible and relieve symptoms. The standard first aid for burning solutions in the eye is irrigation with water. 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, a hypertonic amphoteric 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.
Anticholinergics can work like some antihistamines 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.
Oral analgesics may help relieve eye pain.