Tear gas (a name for a collection of compounds designed to induce pain through severe irritant means, whether in the eyes, skin or lungs, often o-chlorobenzylidene aka “CS”) has been studied by our own military. This showed that in military recruits, who are generally young and healthy, exposure to CS more than doubles the rate of pneumonia, bronchitis and viral illness following exposure. People die from each of these diseases every day. This suggests likely significant airway damage in healthy lungs, since this is data for young healthy military recruits in basic training. We know that those protesting for civil rights also include the elderly, children and medically vulnerable, therefore the rates of those affected and sickened will be higher. We certainly also have police officers serving who have chronic medical conditions including asthma and COPD. A 2016 re-evaluation of what is known about these “tear gas” agents noted that studies regarding safety of these chemicals focused on animal models and young healthy military recruits, which makes sense as these were initially weapons of war (though now banned under the Geneva conventions).  Releasing this chemical on a general population cannot be characterized as a “non-lethal” intervention at the population level. There are surely people who will die from this tool if deployed in large numbers. Asthma affects around 11% of the population in Oregon, and tear gas can be a lethal cause of bronchospasm, provoking severe respiratory distress and potential sudden respiratory collapse in people with asthma. Indiscriminately firing tear gas into a crowd will have the risk of killing people, and it must be considered as an intervention with the potential for lethal effect.

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. 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. That 2016 re-evaluation found concerns 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.