Tear gas: More than Tears

By Geewananda Gunawardana Ph.D.
Pharmaceutical Consultant
Boston, MA, USA

Chemical weapons were used for the first time in 1915 by German army in the battlefield against French army during WWI. Both French and British armies retaliated by using chlorine and mustard gas. Reportedly, Hitler himself fell victim to a mustard gas attack just before the end of the war. Even though both Germany and Allies had manufactured vast stockpiles of a range of chemical weapons, they were not used in the European theatre by either party during the WWII, except in German concentration camps. According to historians, it was Hitler’s firsthand experience that prevented their use despite pressure from his military leaders. After the end of the war, the American weapons manufacturers were desperate to find a peacetime use of their products. With the help of powerful lawyers, media moguls, and politicians, they convinced the police departments to use a non-lethal form of chemical weapons for crowd control during labour disputes erupted between the Blacks and Whites in the postwar USA. Since then, a range of chemicals have been developed as Riot Control Agents (RCA), and they are collectively known as “tear gas” referring to their most obvious physiological effect.

The Chemical Weapons Convention (CWC) was signed in 1993 by 193 countries and came to effect on April 29th, 1997. Ironically, it bans the use of chemical weapons in warfare, but it left some loopholes to allow their use for domestic purposes. It is estimated that the global tear gas market will be about US $ 11 billion in 2023. The major manufacturing countries are Brazil, China, South Africa, South Korea, UK, and USA.

There are four chemical agents used as RCA: O-chlorobenzylidene malononitrile (CS), 1-chloroacetophenone (CN), dibenz[b,f]-1,4-oxazepine (CR), and oleoresin capsicum (OC). Even though they are called “tear gas,” they are solids, and made into aerosols by formulating into pyrotechnic mixtures for dispensing as smoke or fog. Often, the ingredients used in pyrotechnic formulations are toxic compounds themselves.

While the immediate physiological effects of these agents are painfully visible, the detailed epidemiology or the adverse health effect related to their exposure is not well published as they are considered classified information. Ironically, those who have the capabilities to do such research are the ones that manufacture them. Who would want to admit or publish that their products have defects? However, available data indicates that even though tear gas is considered a non-lethal weapon, its use has caused numerous chronic and acute health events and deaths. Recall that it took about hundred years for the tobacco industry to admit that smoking is a health hazard. USA did not sign the landmine treaty (APL) until June 2022 even though it went into effect in 1997. Money talks.

An important fact emerges from the available scientific data: the cellular target of RCA has been identified as a family of proteins called transient receptor potential proteins (TRP). They are part of the biological mechanism responsible for detecting heat, mechanical damage, and noxious agents (nociception). These same proteins (TRPV1 and TRPA1), which form ion channels have been associated with the etiology of several diseases: acute myocardial infarction (AMI), asthma, chronic obstructive pulmonary disorder (COPD), cardiac arrhythmias, dermatitis, immune disorders, and peripheral nerve damage from diabetes. There are indications that exposure to RCA can aggravate these conditions depending on the extent of the exposure. The use of RCA in enclosed areas, drifting of the smoke or fog into dwellings, and misuse are known to result in severe cases of injury including miscarriages and death. Children and women can be at higher risk due to their lower body mass compared to adult males.

Furthermore, the RCA belong to a class of chemicals known as electrophiles, which are known to have genotoxic and mutagenic properties and are strictly regulated in pharmaceuticals, for example. No such quality controls exist for RCA, and further studies are needed to evaluate the genotoxic and mutagenic properties of RCA that could result in birth defects and cancer. In addition, the toxicity of the degradation products of RCA formed during pyrotechnic deployment and on aging has not been investigated.

Someday, the world will look at RCA differently, just as the industry and regulatory powers have come to recognise the health hazards of items people use at will such as tobacco, talcum powder, and certain food dyes and regulated them. Future generations will look down upon the use of RCA just as we look back on bloodletting or lobotomy as therapies. Hopefully, people will elect leaders who will not poison their own people, endanger the health of future generations, and ruin the environment. Or, use them according to international conventions at a minimum. Till then, it makes sense for the people who have related pre-existing conditions to avoid potential exposure to RCA.