In the first season of the Air Health Our Health podcast and website, my hometown of Portland, OR was rocked by widespread use of teargas on individuals of all ages at protests in the wake of the death of George Floyd in the summer of 2020. After hearing them referred to as non-lethal, that was the first time I explored the medical literature and realized that they were banned for use in war, and the robust health concerns about their use. I released a podcast episode and two posts in 2020 about health impacts of teargas and submitted health testimony and assisted Oregon Justice Resource Center with an amicus brief about the health concerns. We are now seeing teargas again inundating communities with unknown potential lifelong health consequences. From Chilean data, we know that infants in particular are at high risk, and a 6 month old in Minnesota teargassed in her car required CPR.
I am a member of Oregon Thoracic Society, the state chapter of the American Thoracic Society, which was founded in 1905 and is comprised of over 22,000 members engaging in care of patients and science related to respiratory health and threats to it. The American Thoracic Society at the time called for a moratorium on its use after review by the ATS Section on Bioterrorism and Inhalational Disasters, a call which they have reiterated in 2026. The ATS Section on Terrorism and Inhalational Disasters contains a specific locus of expertise regarding the impact of CS and Capsaicin oleoresin capsicum = OC, partially replaced by PAVA (nonivamide) a synthetic variant from both cell culture to mouse models to studies in humans.
Tear gas is not actually a gas, but an aerosolized powder generally mixed into a pyrotechnical charge, and the ignition of the same when used in munition forms such as pepper balls, grenade varieties can combine to generate other highly concerning chemicals, such as hexavalent chromium, a known carcinogen. Our own military has conducted research on the resulting chemical clouds from deployment of teargas agents, and found a host of known inhalation and liver toxins as well as cyanide formation.
These chemicals bind receptor channels (TRPV1 and TRPA1) in nerves both in the eyes and skin as well as in the respiratory tract, causing inflammation in the airways, reduced lung function, and at extremes lung collapse, lung failure and rarely death. There are also concerns about elevating blood pressure, changes in reproductive cycle, and more. One of the receptors for capsaicin is the TRPA1 receptor, which also seems to maintain asthmatic inflammation. The stimulation of many of these nerves actually leads to more and ongoing inflammation, not just pain without harm.
As a lung doctor, I can say that I have had to send patients to the ER after exacerbations from far less noxious compounds. I even had one patient with severe asthma/COPD overlap syndrome come close to respiratory arrest in my office lobby because someone was wearing perfume. With more than 1 in 10 Oregonians suffering from asthma, this is very dangerous to our population, whether the individual targeted by law enforcement deployment of agents, the surrounding community, or the law enforcement officers themselves. I have a patient with obstructive lung disease who is a senior citizen, and teargas sprayed in her neighborhood entered her home and caused days of illness for her.
Our armed forces have studied tear gas in the form of CS (o-chlorobenzylidene), and have found that rates of viral illness and pneumonia double in the weeks following exposure, even in young healthy military recruits. A study of people repeatedly exposed to teargas showed worsened lung function and symptoms of airway disease and damage in those exposed. The more enclosed the space, the higher the risk, as in the case of the prisoners dying in a transport into which a teargas canister was fired. Members of our community as well as police officers suffer from conditions such as asthma and COPD, and if young healthy military recruits can suffer airway damage, these community members will be particularly vulnerable. Widespread use of teargas in protests in Chile were of particular risks to infants in the population, who obviously were not engaged in protest activity.
When we study medications to determine their safety in people, we look at them in large populations and document the comorbidities of those exposed to the substance. Declaring a substance “safe” in the absence of these studies is likely an error, and does not pass the plausibility test if the population exposed includes those with underlying airway disease, particularly for substances known to cause actual burn injury on the skin. This has been the conclusion of others reviewing the literature as well (see references below). Like anything in medicine, we have to think not only about the active ingredient of the substance, but also what it is “mixed” in. Tear gas is not actually a gas but solids deployed in liquid form either from a pressurized dispenser as a spray or aerosolized via mixture of a powdered chemical form with a pyrotechnic mixture. There is concern for significant toxicity with these mixtures. For example, CS is generally only 45% of the mixture, with the rest including chemicals like maleic anhydride, epoxy resin, etc and generally aerosolizes in 3 to 10um microparticles. Sprays are often dispersed in methyl isobutyl ketone (hexone), which is another potentially hazardous compound.
I work in a life-and-death field. I know the surge of adrenaline that occurs in situations with lives at risk, and we are trained to think clearly in these situations. I have also worked with patients that have been violent or verbally abusive towards me and other staff. We train very carefully in how to de-escalate and control these scenarios, and have precise ethical steps we are empowered to take depending on the situation. We always weigh the risks and benefits of each intervention along with patient and staff safety. When I am working with patients in the clinic with high deductibles and the “donut hole,” we also think about the costs of each medication vs its benefit to their lives. Tear gas is a “high cost” substance in both human health and downstream healthcare expenditures to treat those suffering from its exposure. It is time for careful reflection on the true risks and benefits of tear gas.
I am participating in a panel at the Interdisciplinary Association for Population Health Science meeting on teargas events in Portland, OR and re-reviewed the literature. I am including a relevant updated list of references here.
To sum- these agents should in general not be used or deployed, especially in their munitions format. In places where a complete moratorium is not passed, the ATS has recommendations for harm mitigation if teargas is going to be used, which include:
1- Education of all users of CS, OC or derivatives about potential serious health impacts and potential lethality of use.
2- If used, used only after sufficient warning and as a last resort
3- Use must be restricted to open areas – significant concern for indoor use, use in vehicles etc as particularly high risk
4- Mandate health screenings for any individuals exposed and clarity about agent to which they were exposed as well as propellant
5- Never use when children, pregnant women or elderly are present
6- Egress from agent use must be preserved- ie no use where exposed individuals cannot escape the effects, avoidance of kettling tactics, etc
7- Immobilized individuals should never be sprayed with the agent or intentionally exposed while immobilized
References:
Achanta S, Chintagari NR, Balakrishna S, Liu B, Jordt SE. Pharmacologic Inhibition of Transient Receptor Potential Ion Channel Ankyrin 1 Counteracts 2-Chlorobenzalmalononitrile Tear Gas Agent-Induced Cutaneous Injuries. J Pharmacol Exp Ther. 2024 Jan 17;388(2):613-623.
Brown JL, Lyons CE, Toddes C, Monko T, Tyshynsky R. Reevaluating tear gas toxicity and safety. Inhal Toxicol. 2021 May-Jul;33(6-8):205-220.
Brown L, Takeuchi D, Challoner K. Corneal abrasions associated with pepper spray exposure. Am J Emerg Med. 2000 May;18(3):271-2.
Chung S, Baum CR, Nyquist AC; DISASTER PREPAREDNESS ADVISORY COUNCIL, COUNCIL ON ENVIRONMENTAL HEALTH, COMMITTEE ON INFECTIOUS DISEASES. Chemical-Biological Terrorism and Its Impact on Children. Pediatrics. 2020 Feb;145(2):e20193750.
Dagli, E. , Uslu E., Ozkan G., et al 2014. Respiratory effects of tear gas exposure on innocent by‐standers. Accessed May 20, 2016.
Dimitroglou Y, Rachiotis G, Hadjichristodoulou C. Exposure to the riot control agent CS and potential health effects: a systematic review of the evidence. Int J Environ Res Public Health. 2015 Jan 27;12(2):1397-411.
Haar, R.J., Iacopino, V., Ranadive, N. et al. Health impacts of chemical irritants used for crowd control: a systematic review of the injuries and deaths caused by tear gas and pepper spray. BMC Public Health 17, 831 (2017).
Hill AR, Silverberg NB, Mayorga D, Baldwin HE. Medical hazards of the tear gas CS. A case of persistent, multisystem, hypersensitivity reaction and review of the literature. Medicine (Baltimore). 2000 Jul;79(4):234-40.
Horton DK, Burgess P, Rossiter S, Kaye WE. Secondary contamination of emergency department personnel from o-chlorobenzylidene malononitrile exposure, 2002. Ann Emerg Med. 2005 Jun;45(6):655-8.
Huerta PA, Cifuentes M, González M, Ugarte-Avilés T. Tear gas exposure and its association with respiratory emergencies in infants and older adults during the social uprising of 2019 in Chile: an observational, longitudinal, repeated measures study. BMJ Open. 2023 Jun 6;13(6):e067548.
Ifantides C, Christopher KL, Deitz GA, et al. Ophthalmic Injuries by Less-Lethal Kinetic Weapons During the US George Floyd Protests in Spring 2020. JAMA Ophthalmol. 2021;139(2):242–244.
Joseph J. Hout, MS USA, Duvel W. White, MS USA, Anthony R. Artino, MSC USN, Joseph J. Knapik, ScD, o-Chlorobenzylidene Malononitrile (CS Riot Control Agent) Associated Acute Respiratory in a U.S. Army Basic Combat Training Cohort. Military Medicine, Volume 179, Issue 7, July 2014, Pages 793–798
Kales SN, Christiani DC. Acute chemical emergencies. N Engl J Med. 2004 Feb 19;350(8):800-8.
Karaman E, Erturan S, Duman C, Yaman M, Duman GU. Acute laryngeal and bronchial obstruction after CS (o-chlorobenzylidenemalononitrile) gas inhalation. Eur Arch Otorhinolaryngol. 2009 Feb;266(2):301-4.
Kim YJ, Payal AR, Daly MK. Effects of tear gases on the eye. Surv Ophthalmol. 2016 Jul-Aug;61(4):434-42.
Olajos EJ, Salem H. Riot control agents: pharmacology, toxicology, biochemistry and chemistry. J Appl Toxicol. 2001 Sep-Oct;21(5):355-91.
Shah, A., J. Therkorn, M. Arjomandi, M.J. Falvo, N. Jani, S.D. Krefft, J.J. Osterholzer, A.M. Sotolongo, and S.E. Hines. Laryngeal Hypersensitivity in a Veteran Cohort with Remote Exposure to Tear Gas and Pepper Spray [abstract]. Am J Respir Crit Care Med 2022;205:A3842.
Stopyra JP, Winslow JE 3rd, Johnson JC 3rd, Hill KD, Bozeman WP. Baby Shampoo to Relieve the Discomfort of Tear Gas and Pepper Spray Exposure: A Randomized Controlled Trial. West J Emerg Med. 2018 Mar;19(2):294-300.
Thomas RJ, Smith PA, Rascona DA, Louthan JD, Gumpert B. Acute pulmonary effects from o-chlorobenzylidenemalonitrile “tear gas”: a unique exposure outcome unmasked by strenuous exercise after a military training event. Mil Med. 2002 Feb;167(2):136-9.
Torgrimson-Ojerio, B.N., Mularski, K.S., Peyton, M.R. et al. Health issues and healthcare utilization among adults who reported exposure to tear gas during 2020 Portland (OR) protests: a cross-sectional survey. BMC Public Health 21, 803 (2021).
Treudler R, Tebbe B, Blume-Peytavi U, Krasagakis K, Orfanos CE. Occupational contact dermatitis due to 2-chloracetophenone tear gas. Br J Dermatol. 1999 Mar;140(3):531-4.
Zollman TM, Bragg RM, Harrison DA. Clinical effects of oleoresin capsicum (pepper spray) on the human cornea and conjunctiva. Ophthalmology. 2000 Dec;107(12):2186-9.
