Tear Gas: Composition, Mitigation, and COVID-19 Implications

Photo: toxic tear gas clouds photographed by Alisdare Hickson.


Despite being banned for wartime use shortly after World War I (Geneva Protocol, 1925), tear gas is still a crowd dispersion method commonly employed by police forces during domestic conflict. Recently, there has been an extreme uptick in international usage of tear gas as tensions escalate between civilians and police at protests against police brutality. These conflicts are heightened by the deaths of many African American citizens as a result of excessive force and poor judgement on behalf of law enforcement. With such widespread protest comes an increased risk of being subject to tear gas, which is why it is more important than ever to understand its composition, mitigation techniques, and COVID-19 health implications.


According to Sven Eric Jort, a pain pharmacologist and toxicologist at Duke University, the composition of a tear gas canister is similar to that of fireworks. An average tear gas canister contains charcoal, potassium nitrate (KNO3), potassium chlorate (KClO3), silicon (Si), magnesium carbonate (MgCO3), sucrose (C12H22O11), and O-Chlorobenzalmalononitrile (C10H5ClN2), or CS gas. When initially ignited, the charcoal inside the tear gas canister will catch fire, acting as a catalyst for the reaction to take place. Potassium nitrate serves the purpose of helping charcoal burn at a more rapid pace, while acting with potassium chlorate to produce oxygen to further fuel the flames. Potassium chlorate then breaks down into potassium chloride gas, which forms into droplets with the help of silicon. Magnesium carbonate, which acts as a pH buffer in water, keeps the pH within the canister from dropping too low, as a low pH could destabilize the potassium chlorate. Sucrose, or sugar, burns at a fairly low temperature, and helps convert tear gas’s key ingredients into noxious fumes. O-Chlorobenzalmalononitrile, or CS gas, is the key ingredient of tear gas, and creates a pungent gas when heated. All of these reactions take place within a canister covered in a sticky, flammable compound called nitrocellulose {[C6H7(NO2)3O5)n]}.


  • Coughing

  • Respiratory inflammation

  • Asthma attacks

  • Burning eyes and skin*

  • Nausea

  • Vomiting

* CS gas activates the mucous membranes of the eyes, mouth, and nose, as well as a receptor in a network of nerve fibers found all over the human body called peripheral sensory nerves. This receptor can also be activated by natural products such as mustard and wasabi. Tear gas is much more potent than said natural products, which is why it causes much more pain.


When protesting:

  • Wear eye protection and face coverings. Goggles, face shields, glasses, and masks protect facial orifices from tear gas particles, making the ordeal less painful for the protester.

  • Do not wear contact lenses. According to Dr. Ian Wittman, chief of emergency medicine at NYU Langone Hospital in Brooklyn, “leaving the contact lenses in with an irritant is dangerous and can lead to corneal ulcers, breaking down the thin layer of tissue that overlies your eye”. Wittman instructs those exposed while wearing contacts to “immediately use saline solution to flush your eyes out and remove the contact lenses”.

  • Do not wear makeup. According to Natasha Bhuyan, an internal medicine provider at OneMedical, “it’s better to not wear makeup because tear gas can cling to things like mascara or lipstick”.

If exposed to tear gas:

  • Move to a safe area.

  • If you are wearing contact lenses, have somebody with clean hands remove them for you.

  • Flush out your eyes using water or saline solution. Do not use milk or a baking soda solution; milk is only effective against pepper spray and may cause infection when used against tear gas, and baking soda is an irritant which may cause abrasions in the eyes and skin. In addition, a 2018 study published by the Western Journal of Emergency Medicine indicates that baking soda solutions and baby shampoo are no more effective at reducing discomfort than water. Water is the safest and most accessible tool, and is the least likely to lead to abrasions and infections.

  • Rinse out your nose and mouth with water to remove tear gas particles.

  • As soon as you are able to, take a shower. Use strong dish soap on all affected areas of the body to further remove tear gas particles. This step will be painful, but is necessary in cleansing yourself of harmful chemicals.

  • If you’re still experiencing blurred vision 15-30 minutes after being tear gassed, or if you’re struggling to breathe after you have left the area of exposure, see a medical provider immediately.


While there is no proven method to fully neutralize deployed tear gas, protesters around the world have come up with various ways of preventing the reaction from reaching completion. Their methods include but are not limited to the following:

  • Blowing the canister away with a leaf blower

  • Covering the canister with a traffic cone and dousing it in water

  • Putting canisters in sealed containers filled with nonvolatile liquids

Sven Eric Jordt, a pain pharmacologist and toxicologist at Duke University, recommends putting the tear gas canister in mud. According to Jordt, mud extinguishes the burning components, blocks the canister’s oxygen supply, and plugs openings where aerosol could come out, effectively rendering the canister as useless. Mud is also accessible, and can be easily found outdoors.


According to Jordt, CS gas, the key ingredient of tear gas, is known to cause inflammation and injuries to the airway by burning the skin upon inhalation. Jordt asserts that “using it in the current situation with COVID-19 around is completely irresponsible. There is sufficient data proving that tear gas can increase the susceptibility to pathogens, to viruses”.

Jordt’s statement is not unfounded. A 2014 study conducted by the U.S. Army found that tear gas exposure creates a higher likelihood of contracting respiratory diseases like the common cold and flu, as tear gas depletes and compromises most antiviral defenses that reside within the human body. These findings are further buttressed by a 2020 study published in the National Library of Medicine, which shows an association between contraction of COVID-19 and smoke inhalation. The study reveals that smoke inhalation depresses the human pulmonary immune system, which creates a greater risk of contracting infectious diseases and causes complications in recovery from said diseases. Dr. John Balmes, a pulmonologist at the University of California San Francisco and an excerpt with the American Thoracic Society, agrees. “I actually think we could be promoting COVID-19 by tear-gassing protestors,” Balmes divulges, “It causes injury and inflammation to the lining of the airways.” Balmes believes that this inflammation, which causes setbacks for the body’s antiviral defenses, creates a higher probability that someone who has been in contact with the virus will contract it. Balmes adds that “these exposures to tear gas would increase the risk of progression from the asymptomatic infection to a symptomatic disease.”

In addition to shutting down the body’s defenses against viral infection, Dr. Amesh Adalja, who works for John Hopkins University and is a spokesperson for the Infections Diseases Society of America, says that people may shed more of the virus as a result of a reaction with tear gas chemicals. Adalja anticipates a spike in COVID-19 infractions, adding that “we know that any kind of social unrest, especially in the midst of an outbreak, is going to make things worse”, citing the cholera outbreak caused by bombings in Yemen.

However, despite the increase in COVID-19 cases, many physicians and healthcare professionals still stand in solidarity with the protesters. In the past week, thousands of medical workers have signed an open letter in support of the anti-racism and anti-police brutality demonstrations, which recommends ways that protesters, police, and politicians can minimize the spread of COVID-19. One of the major recommendations: abolish the use of pepper spray and tear gas.


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