German troops make their way through a cloud of smoke or gas during a gas training drill, circa 1916. Henry Guttmann/Hulton Archive via Getty ImagesChemical warfare is one of the most devastating forms of conflict. It leverages toxic chemicals to disable, harm or kill without any physical confrontation. Across various conflicts, it has caused tens of thousands of deaths and affected over a million people through injury and long-term health consequences.Mustard gas is a class of chemical that isn’t a gas at room temperature – it’s a yellow-brown oily liquid that can vaporize into a toxic mist. Viktor Meyer refined the synthesis of mustard into a more stable form. Mustard gas gained international notoriety during World War I and has been used as a weapon many times. German soldiers release poison gas from cylinders during World War I. Henry Guttmann Collection/Hulton Archive via Getty Images It is nearly impossible to guarantee that mustard gas will never be used in the future, so the best way to prepare for the possibility is to develop a very easy way to detect it in the field. My colleagues and I, who are chemists and materials science researchers, are keen on developing a rapid, easy and reliable way to detect toxic chemicals in the environment. But doing so will require overcoming several technological challenges.Effects on human health and communitiesMustard gas damages the body at the cellular level. When it comes into contact with the skin or eyes or is inhaled, it dissolves easily in fats and tissues and quickly penetrates the body. Once inside the body, it changes into a highly reactive form that attaches to and damages DNA, proteins and other essential parts of cells. Once it reacts with DNA, the damage can’t be undone – it may stop cells from functioning properly and kill them.Mustard gas exposure can trigger large, fluid-filled blisters on the skin. It can also severely irritate the eyes, leading to redness, swelling and even permanent blindness. When inhaled, it burns the lining of the airways, leading to coughing, difficulty breathing and long-term lung damage. Symptoms often don’t appear for several hours, which delays treatment. The forearms of test subjects exposed to nitrogen mustard and lewisite, chemicals that cause large, fluid-filled blisters on the skin. Naval Research Laboratory Even small exposures can cause serious health problems. Over time, it can weaken the immune system and has been linked to an increased risk of cancers due to its effects on DNA. The effect of just one-time exposure carries down to the next generation. For example, studies have reported physical abnormalities and disorders in the children of men who were exposed to mustard gas, while some of the men became infertile.The best way to prevent serious health problems is to detect mustard gas early and keep people away from it.Detecting mustard gas earlyThe current methods to detect mustard gas rely on sophisticated chemistry techniques. These require expensive, delicate instruments that are difficult to carry to the war front and are too fragile to be kept in the field as a tool for detecting toxic chemicals. These instruments are conventionally designed for the laboratory, where they stay in one location and are handled carefully. Many researchers have attempted to improve detection techniques. While each offers a glimpse of hope, they also come with setbacks.Some scientists have been working on a wearable electrochemical biosensor that could detect mustard gas in both liquid and vapor form. They succeeded in developing tiny devices that provide real-time alerts. But here, stability became a problem. The enzymes degrade, and environmental noise can cloud the signal. Because of this issue, these strips haven’t been used successfully in the field. To simplify detection, others developed molecularly imprinted polymer test strips targeting thiodiglycol, a mustard gas breakdown product. These strips change color when they come into contact with the gas, and they’re cheap, portable and easy to use in the field. The main concern is that they detect a chemical present in the aftermath of mustard gas use, not the agent itself, which isn’t quite as effective. One of the most promising breakthroughs came in 2023 in the form of fluorescent probes, which change color when they sense the chemical. This probe is a tiny detective tool that detects or measures the target chemical and generates a signal. But these probes remain vulnerable to environmental interference such as humidity and temperature, meaning they’re less reliable in rugged field conditions.Some other examples under development include a chemical sensor device that families could have at home, or even a wearable device. Wearable devices are tricky, however, since they need to be small. Researchers have been trying to integrate tiny nanomaterials into sensors. Other teams are looking at how to incorporate artificial intelligence. Artificial intelligence could help a device interpret data faster and respond more quickly.Researchers bridging the gapNow at Washington University in St Louis, Makenzie Walk and I are part of the team of researchers working on detecting these chemicals, led by Jennifer Heemstra and M.G. Finn. Another member is Seth Taylor, a postdoctoral researcher at Georgia Tech. Our team of researchers hopes to use the lessons learned from prior sensors to develop an easy and reliable way to rapidly detect these chemicals in the field. Our approach will involve testing different molecular sensor designs on compounds modeled after specific chemical weapons. The sensors would initiate a cascade of reactions that generate a bright, colorful fluorescent signal in the laboratory. We are figuring out to which compounds these chemicals react best, and which might make a good candidate for use in a detector. These tests allow us to determine how much of the chemical will need to be in the air to trigger a reaction that we can detect, as well as how long it will need to be in the air before we can detect it.Additionally, we are investigating how the structure of the chemicals we work with influences how they react. Some react more quickly than others, and understanding their behavior will help us pick the right compounds for our detector. We want them to be sensitive enough to detect even small amounts of mustard gas quickly, but not so sensitive that they frequently give falsely positive results. Eliminating the use of these chemicals would be the best approach to avoid future recurrence. The 1997 Chemical Weapons Convention bans the production, use and accumulation of chemical weapons. But countries such as Egypt, North Korea and South Sudan have not signed or officially adopted the international arms control treaty. To discourage countries that don’t sign the treaty from using these weapons, other countries can use sanctions. For example, the U.S. learned that Sudan used chemical weapons in 2024 during a conflict, and in response it placed sanctions on the government.Even without continued use of these chemical weapons, some traces of the chemical may still linger in the environment. Technology that can quickly identify the chemical threat in the environment could prevent more disasters from occurring. As scientists and global leaders collectively strive for a safer world, the ability to detect when a dangerous chemical is released or is present in real time will improve a community’s preparedness, protection and peace of mind.Mekenzie Walk and Jen Heemstra contributed to this article.Heemstra lab receives funding from the Defense Threat Reduction Agency (DTRA).