It’s hard to imagine modern life without glycols. They are used in cosmetics, fog machines, and food. As you read this, you’re almost certainly wearing or drinking from something they were used to produce — polyester fabric or plastic bottles, for example. If you brush your teeth with toothpaste or top your salad with bottled dressing, you’ve come into contact with these manmade chemical compounds. 

Manufactured at industrial scales from crude oil and natural gas, glycols are a common antifreeze ingredient. They are also useful for refrigeration, allowing cooling systems to maintain colder temperatures than water alone allows. 

But there’s something more they could do for us: When glycols are vaporized into indoor air, they rapidly inactivate viruses, bacteria, and fungal spores — even while the glycol vapors remain at low enough concentrations to be invisible, odorless, and tasteless. It’s a property that could reduce the spread of the seasonal flu, and maybe even help stop airborne pandemics before they begin. We’ve known about their disease-fighting properties for almost a century, and new research might allow us to deploy them at scale soon. 

Chemically speaking, glycols are organic compounds that belong to the alcohol family. Propylene glycol (PG), dipropylene glycol (DPG), and triethylene glycol (TEG) vapors specifically seem safe for humans to breathe. TEG vapors in particular would be cheap to deploy — costing only about 10 to 50 cents per day to protect a 1,000-square-foot room. While it’s not exactly clear how they combat pathogens, they’ve been shown to inactivate both air- and surface-borne viruses and prevent respiratory disease transmission. According to Curtis Donskey, an infectious disease physician and researcher at the Cleveland VA Medical Center, glycol vapors are particularly effective against enveloped viruses — think SARS-CoV-2, influenza, and Ebola.

There’s a body of evidence supporting their use for infection prevention dating back to the mid-20th century. One study conducted over three winters between 1941 and 1944 in a pediatric hospital demonstrated a 96 percent reduction in colds in wards that were disinfected with glycol vapors, compared to those that weren’t. Patients in the glycol-treated wards also had 90 percent fewer total cases of tracheobronchitis, middle ear infections, and acute pharyngitis than the controls.    

That research is many decades old, of course, and even similar studies would employ different methodologies today. “Different times [mean] different research standards,” Jacob Swett, the executive director and founder of Blueprint Biosecurity, a nonprofit focused on pandemic prevention, told me. “But I think this shows where the potential could be.”

People in the mid-20th century saw a market opportunity in glycol vapors’ ability to reduce disease transmission. Newspaper advertisements touted “glycolators” and “glycolizers” to protect homes and office spaces.  

Interest in glycol vapors for disinfection peaked in the 1940s, falling off with the advent of widely available antibiotics. There was a spike in peer-reviewed papers on glycols in the 1980s, mostly focused on their use in cooling systems and antifreeze agents as disinfectants, but broader interest remained minimal. 

The Covid-19 pandemic brought renewed interest in glycol vapors’ antimicrobial properties, and the Environmental Protection Agency (EPA) issued an emergency approval in six states for a TEG-based product series to disinfect occupied indoor spaces. But scientific research on the subject remained relatively limited. Public health agencies were often skeptical about using glycol vapors for disinfection during the Covid-19 pandemic, when the safety profiles of other mitigation measures were better understood. Public health bodies were working with the information they had — some of which turned out to be outright incorrect, like the insistence that SARS-CoV-2 was spread only by droplets rather than being airborne. Hence the stronger focus, especially in the early phases of the pandemic, on measures such as social distancing, practices that are less effective for diseases in which pathogens travel farther and remain suspended in the air.

But even if early speculation about droplet-based transmission of Covid had been correct, there would have been plenty of other good reasons to take the pathogen-negating properties of glycol vapors seriously. “Whether it’s tuberculosis, SARS-CoV-2, the seasonal flu [that] threatens us every year or the next pandemic, which is likely to be airborne, having this evidence around glycol vapors will put us in a much better position to be able to make informed decisions about countermeasures,” Swett told me. With that possibility in mind, Blueprint awarded $4.5 million in grants to the recipients of its Glycol Vapors for Infection Suppression: Efficacy and Safety Research (GlycolISER) program in March. 

The grantees will study how glycol vapors inactivate pathogens, their effectiveness during emergency deployment, real-world efficacy in healthcare settings, and how the vapors interact with air filter media. The researchers will also study glycol vapors’ safety profile, especially with potentially sensitive populations, such as people with asthma. 

“Being ready to fight the next pandemic means we need to robustly evaluate a wide range of possible interventions,” Brian Renda, a program director at Blueprint Biosecurity, said in a press release. “Through this program, we’re supporting multidisciplinary research to better understand the potential and limitations of glycol vapors as a tool to reduce airborne disease transmission.”

Initial findings are expected by early to mid-2027. “We want to know more about how well it works and we want to make sure that it doesn’t have unintended consequences,” Delphine Farmer, a professor of atmospheric chemistry at Colorado State University who is one of the grantees, told me. Her research will examine how best to get glycol vapors into the air in a quick and affordable way, and how much would come out in gases and particles once vaporized, since those factors impact how effective they are at removing and destroying different microbes that might be in the air. “We want to make sure that if people start adding glycol vapors to air, that this doesn’t cause unknown or new chemistry that might negatively impact people. So the third aspect of what we’re doing is to look at polyethylene glycol chemistry and see if it’s going to produce anything or react with surfaces in ways we should be concerned about.” 

Donskey is another of the grantees, and his project has multiple aims. Using a commercially available glycol-based product currently approved for use in unoccupied spaces and for control of mold and mildew, his work will assess whether glycol vapors can reduce the concentration of pathogens in various healthcare settings with different degrees of ventilation.  His research will also, among other things, examine whether glycol vapors can reduce airborne pathogen dispersal in medical procedure rooms. The researchers will start testing in unoccupied rooms and transition to populated spaces after the products receive EPA registration for use in occupied spaces.

As Swett suggests, the next pandemic will very, very likely come at us through the air, but there are already numerous other illnesses circulating that we could prevent before they take root. The potential benefits — for reducing work and school absenteeism, healthcare costs, and avoidable suffering — are enormous. 

Why we need a multilayered arsenal against airborne disease

If the Covid-19 pandemic taught us anything, however, it’s that airborne disease is still a threat as long as we breathe. But six years on, it’s not clear if we took that lesson to heart. “It seems like we didn’t really learn much from Covid-19 and [as a society] are actively ignoring the ongoing effects,” Miles Griffis, the co-founder of The Sick Times, a publication covering long Covid, told me. “I think we could be in a much better place than we are now.”

A study from 2024 found that 400 million people around the world have had long Covid — almost certainly an undercount. In the next 10 years, long Covid could cost health systems $11 billion annually. Up to 35 percent of people infected by Covid-19 develop lingering symptoms that can be profoundly disabling. 

And Covid is only one disease you can catch through the air, nor is it the only one that can have dire consequences. Influenza costs the US almost $29 billion in a single season from healthcare costs and lost productivity — and it kills up to 650,000 people worldwide every year. Childcare centers, schools, and workplaces would be significantly safer and more productive with better ways to prevent the spread of airborne illness. 

It’s impossible to say how many cold or flu or Covid-19 infections glycol vapors could prevent. But, like other technologies such as germicidal ultraviolet light, they are notable in part because they don’t require people to “opt in” the way donning a mask does — their distribution mechanisms could be built into the environment itself. William and Mildred Wells, a husband-and-wife duo, were thinking along these lines in the 1930s, advocating for governments to install germicidal ultraviolet lights in public places to protect everyone from airborne pathogens. The Wellses saw that people were developing ways to purify water, pasteurize milk, and ensure food wasn’t contaminated, and asked “‘What about the air? Don’t we deserve pure air as well?’” Carl Zimmer, a science columnist for the New York Times and the author of Air-Borne: The Hidden History of the Life We Breathe, told me. 

Blueprint Biosecurity thinks so, and is also advancing work on far-UVC light and better personal protective equipment to protect against airborne pathogens. Better ventilation and filtration could, of course, also improve indoor air quality, which would significantly reduce respiratory disease transmission.  

“In many ways, the kind of changes to buildings today [compared to the 1940s and ’50s when earlier studies were done] potentially make them more amenable to glycol vapors where you have centralized HVAC systems,” Swett told me. “[And] depending on how the evidence comes back, there’s a number of environments where you could imagine deploying them.”

“I think we’ve got a little bit of testing to go before we know how well they work,” Farmer said. “As an atmospheric chemist, I always think about clean air…as the absence of any pollutant. So the moment I hear about adding anything to air, I have some notes of caution. But on the flip side, we do add things to our indoor air all the time, so it doesn’t necessarily mean it’s a dealbreaker.”  

No matter how safe and effective glycol vapors prove to be, there’s likely to be resistance of one kind or another. People will be wary of adding substances to the air, and entering spaces where they don’t know if glycol vapors will be used. But Donskey doesn’t anticipate that this will be a major issue: “If a product has an EPA registration indicating that they believe it’s safe for use in occupied areas, I think most people will be comfortable. There may be some people who are less comfortable, but again, I think it’ll go through more safety evaluations.”  

Once a regulatory agency says this is safe to use in occupied areas, the rest will follow. We would still need commercial products to disseminate them; people can’t just put glycol vapors into their home humidifier. “But if it’s EPA-registered, relatively inexpensive, easy to use, and doesn’t involve a lot of labor, I could easily envision a lot of healthcare facilities taking this up,” Donskey said. 

There are many potential use cases for glycol vapors, and “we definitely need some good strategies that allow for safe indoor environments,” Farmer told me. After all, we spend about 90 percent of our time indoors, and we always have to breathe.

Source: Vox.