Tear gas

As with all non-lethal or less-lethal weapons, there is some risk of serious permanent injury or death when tear gas is used.[6][7][1] This includes risks from being hit by tear gas cartridges that may cause severe bruising, loss of eyesight, skull fracture, resulting in death.[8] 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%),[9] as well as instances of head injuries in young people.[10]

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[2] and may sometimes require hospitalization or even ventilation support.[11] Skin exposure to CS may cause chemical burns[12] or induce allergic contact dermatitis.[2][3] 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.[13] Frequent or high levels of exposure carry increased risks of respiratory illness.[1] During the 2019 Hong Kong protests, some online posts have alleged that teargas, particularly those manufactured in China or past their use-by dates, could give off highly toxic dioxins and cyanide gas. The Hong Kong government declared: “The Department of Health and Hong Kong Poison Information Centre of Hospital Authority have reviewed relevant medical literature and scientific evidence but have found no literature or scientific evidence on dioxin poisoning cases caused by the use of tear gas”.[14]

Reports of expired tear gas canisters picked up by protesters in Egypt led to theories that it could be more toxic, but Steve Wright of Leeds Metropolitan University said if enough time has elapsed that the chemicals have broken down inside the can, then it makes the canister less effective.[15]

Site of Action

TRPA1 ion channel expressed on nociceptors has been implicated as the site of action for CS gas, CR gas, CN gas (phenacyl chloride) and bromoacetone in rodent models.[16][17]

Use of tear gas in warfare, as with all other chemical weapons, is prohibited by various international treaties[NB 2] that most states have signed. Police and private self-defense use is not banned in the same manner. Armed forces can legally use tear gas for drills (practicing with gas masks) and for riot control. Tear gas exposure is a standard 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.[18][19][20][21] First used in 1914, xylyl bromide was a popular tearing agent since it was easily prepared.

The US Chemical Warfare Service developed tear gas grenades for use in riot control in 1919.[22]

Certain lachrymatory agents, most notably tear gas, are often used by police to force compliance.[7] 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 which comes in small spray cans. Versions including CS are manufactured for police use.[23] Xylyl bromide, CN and CS are the oldest of these agents. CS is the most widely used. CN has the most recorded toxicity.[2]

Typical manufacturer warnings on tear gas cartridges state "Danger: Do not fire directly at person(s). Severe injury or death may result."[24] Such warnings are not necessarily respected, and in some countries, disrespecting these warnings is routine. Israeli soldiers have been documented by B'Tselem firing tear gas canisters at activists, some of which resulted in fatalities, though the Israel Defense Forces insist that they maintain a strict policy of only indirect firing.[25][26] Amnesty International criticized the usage of tear gas by Venezuelan authorities noting canisters being fired directly at individuals, causing the death of at least one demonstrator, while also being shot into residential buildings.[27]

However, 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.[28] For example, this occurred during the 2013 protests in Brazil, 2014 Hong Kong protests, 2019 Hong Kong anti-extradition bill protests and both the 2014 and 2017 Venezuelan protests. Also in Iraq 2019 where the Iraqi government used expired tear gas and since 2014 , the Iraq security have used it and killed over 300 protesters in Red October 2019. [Source?]

A variety of protective equipment may be used, including gas masks and respirators. In riot control situations, protesters sometimes use equipment (aside from simple rags or clothing over the mouth) such as swimming goggles and adapted water bottles.[29]

It has been suggested that "The use of masks that filter solid particles is effective, if and only if, the membrane manages to catch particles with sizes smaller than 60 microns".

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[30][31][32] with Venezuelan chemist Mónica Kräuter recommending the usage of diluted antacids as well as baking soda.[33] There have also been reports of these antacids being helpful for tear gas,[34] and for capsaicin-induced skin pain.[35]

During the 2019 Hong Kong protests, frontline protesters have become adept at extinguishing tear gas: they have 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.[36]

Vinegar, petroleum jelly, milk and lemon juice solutions have also been used by activists.[43][44][45][46] It is unclear how effective these remedies are. In particular, vinegar itself can burn the eyes and prolonged inhalation can also irritate the airways.[47] Though vegetable oil and vinegar have also been reported as helping relieve burning caused by pepper spray,[38] Kräuter suggests the usage of baking soda, (not vinegar because it is also an acid), or toothpaste, stating that they trap the particles emanating from the gas near the airways that are more feasible to inhale.[33] A small trial of baby shampoo for washing out the eyes did not show any benefit.[37]Protesters in Chile have been using a 10% bicarbonate/water solution in spray with some good results.