Why Are Xenon And Argon Banned In Sports?

The World Anti-Doping Agency (WADA) banned xenon and argon in 2014 as hypoxia-inducible factor (HIF) activators. Inhaling xenon raises levels of erythropoietin (EPO), a hormone that spurs the production of red blood cells and so raises the oxygen-carrying capacity of the blood. That can lift an athlete’s endurance unfairly, so both gases remain on WADA’s Prohibited List today.

Back in 2014, xenon and argon became the latest additions to the list of substances and methods banned by the World Anti-Doping Agency (WADA), the body that oversees drug testing across many sporting events. The decision struck a lot of people as odd, since the idea of doping with gases more commonly associated with neon lighting, arc welding, and anesthesia seemed a little weird.

The ban took effect on September 1, 2014, with the two noble gases added under WADA’s category of ‘hypoxia-inducible factor (HIF) activators’, and they remain on the Prohibited List to this day.

What Are Noble Gases?

The chemical elements in group 18 of the periodic table are known as the noble gases: helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn) are all gases under normal conditions. (The synthetic super-heavy element oganesson (Og) sits in the same group, but it is predicted to be a solid rather than a gas, so it does not behave like a typical noble gas.)

The reason they are called ‘noble gases’ is that they are truly noble. In less cryptic terms, it implies their unusual non-reactivity. To be more scientifically specific, noble gases have filled outer electron shells, which makes them quite less inclined to the idea of reacting with other elements at normal pressures and temperatures. This is why they very rarely form compounds with other elements.

It’s interesting to note that when the members of the 18th group were first discovered, they were believed to be awfully rare, as well as chemically inert. That’s why they have also been called ‘rare’ or ‘inert’ gases.

Biological Effects Of Noble Gases

Some noble gases are well known to be biologically active due to their analgesic, sedative and hypnotic properties. This, in addition to the fact that they are mostly inert under normal pressure and temperature conditions, makes noble gases quite useful in many situations/settings.

For instance, common inhalation anesthetics are known to have certain disadvantages, including decreased cardiac output, toxicity etc. In contrast, xenon (a noble gas) also has anesthetic properties, minus the aforementioned disadvantages.

Why Are Xenon And Argon Banned In Sports?

The gas at the center of the concern is xenon, which is bioactive enough to nudge up the oxygen-carrying capacity of human blood. Argon was added to the ban alongside it as a precaution, though the human evidence for argon is much thinner (more on that below).

You might already know that our cells need to maintain proper oxygen levels to keep up their aerobic metabolism and energy generation. Xenon helps with the latter in a rather clever way (Source).

Xenon is one of the few agents that are known for their ability to activate the production of HIF-1α, which triggers other proteins to rush to the rescue of oxygen-deprived tissues. One of those proteins is erythropoietin (EPO), which is basically a hormone that boosts the formation of red blood cells in the bone marrow.

What it really does is stimulates low-level hypoxia (a condition wherein there is a deficiency in the amount of oxygen reaching the tissues). This, in turn, stimulates the body to produce blood so that it does a better job of taking in oxygen. If I have to say the same thing in technical terms, I’d say that the inhalation of xenon increases erythropoietin (EPO) levels, a hormone that increases the oxygen-carrying capacity of the blood by encouraging the formation of red blood cells. It should be noted that, due to the same characteristic, synthetic EPO is used to treat patients with kidney diseases and anemia.

Thus, inhaling xenon could boost your stamina and energy, thereby handing you an unfair advantage over the competition. There is a catch for would-be cheats, though: even if a gas clears out of the body within hours, any EPO it triggers, and the extra red blood cells that follow, can linger for days.

It is worth being honest about how solid the science is. A 2015 randomized controlled trial found that a single sub-anesthetic dose of xenon significantly raised EPO in healthy volunteers, peaking about 24 hours after exposure (Stoppe et al., 2016). That effect is real but modest, and a later systematic review noted that the human data are limited and that no published studies have actually tested whether argon inhalation affects EPO or red blood cell production at all. In other words, WADA banned argon largely by extension from xenon and out of caution, rather than on the strength of direct evidence.

What Is Xenon Used For?

Doping is easily the least common thing xenon does. For a gas this rare and expensive, it earns its keep in some surprisingly varied places.

The most familiar use is lighting. Run an electric current through xenon and it glows with a brilliant, daylight-like light, which is exactly what you want in the high-speed flash bulbs photographers use, in stroboscopic lamps, and in the bright bluish-white headlamps fitted to many cars. The same arc lamps light up cinema projectors and even pump certain lasers.

Out in space, xenon is a favorite propellant for ion engines. Spacecraft such as NASA’s Deep Space 1 and Dawn probes, and Europe’s SMART-1, ionize xenon and fling the charged atoms out the back to generate a small but extremely efficient thrust. In medicine, the heavy isotope xenon-129 can be hyperpolarized and breathed in as a contrast agent so doctors can image lung function on an MRI scan without any ionizing radiation. And in electronics, xenon difluoride (XeF₂) is used to etch silicon when manufacturing the tiny microelectromechanical systems (MEMS) inside sensors and chips (Source).

Can Xenon Be A Solid Or A Liquid?

Yes, though you have to work for it. At everyday room temperature and pressure xenon is a colorless, odorless gas, but chill it far enough and it condenses and then freezes like anything else.

The numbers are striking. Xenon boils at just 165.05 K (-108.1 °C, -162.6 °F) and freezes at 161.40 K (-111.8 °C, -169.2 °F). That leaves a remarkably narrow window of only about 3.6 °C in which xenon stays liquid before turning solid, which is one of the tightest liquid ranges of any element (Source). Solid xenon is a face-centered cubic crystal and, despite being made of a ‘gas’, it is surprisingly dense.

That dense liquid form has a famous job. The LUX-ZEPLIN (LZ) experiment, sitting nearly 1.5 km (about a mile) underground at the Sanford Underground Research Facility in South Dakota, holds roughly 10 tonnes of ultra-pure liquid xenon kept near -100 °C to look for dark matter. If a dark-matter particle ever bumps into a xenon nucleus, the recoil produces a tiny flash of light and a trickle of charge that the detector’s photomultipliers can pick out. Xenon is ideal here precisely because it is heavy and dense, giving more nuclei for a rare particle to hit (Source).

What Happens If You Inhale Xenon?

Breathe in pure xenon and the first thing you would notice is your voice, since it is far denser than air and drops your pitch into a comically deep register, the mirror image of the helium squeak. But the more interesting effects are pharmacological, and they are the reason doctors take xenon seriously.

At high enough concentrations xenon is a genuine anesthetic. Unlike most anesthetics, which work by boosting the brain’s GABA signaling, xenon mainly blocks the NMDA receptor by competing with its co-agonist glycine. That gives it an unusually gentle profile: it keeps the heart rate and blood pressure stable and appears to protect brain tissue from oxygen starvation, which is why it has been trialed alongside cooling to treat newborns with hypoxic-ischemic brain injury (Source). The catch is cost. Xenon must be separated from air in tiny quantities, so a single procedure can run far more expensive than conventional anesthetic gases, which has kept it a niche tool rather than a hospital standard.

One important caveat: like any gas that is not oxygen, breathing xenon outside a controlled clinical setting risks asphyxiation, because it simply displaces the air your body needs. This is firmly not something to try at home.

Does Xenon Actually React With Anything?

Here is where the textbook story about ‘inert’ noble gases breaks down. For decades chemists assumed the noble gases were too unreactive to form compounds at all. Then, in 1962, Neil Bartlett at the University of British Columbia mixed xenon with the powerful oxidizer platinum hexafluoride (PtF₆) and produced a yellow-orange solid, xenon hexafluoroplatinate, the very first compound ever made from a noble gas (Source).

That single result overturned the idea that xenon could never bond and kicked off a whole field of chemistry. Researchers quickly went on to make a family of xenon fluorides, including xenon difluoride (XeF₂), xenon tetrafluoride (XeF₄), and xenon hexafluoride (XeF₆). Xenon manages this because it sits low in the group, so its outer electrons are held loosely enough to be pried away by aggressively electron-hungry partners like fluorine and oxygen. So while xenon is still one of the least reactive elements around, ‘noble’ never quite meant ‘impossible’.