The Air In Hospitals and On Airplanes Is Cleaner Than You Think

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WHumans confine themselves to small spaces for a variety of reasons. Sometimes we pack by the dozen onto airliners bound for Boca. Other times, we are forced to move closer to each other while sitting in hospital waiting rooms.

Especially in the wake of a global respiratory disease pandemic, being in such crowded spaces can cause anxiety. But is the air circulating in airplanes and hospitals filled with airborne pathogens or other toxic substances, as our imaginations sometimes would have us believe?

According to researchers studying air quality in these two common proxies for human sardine cans, it’s not that bad.

New results published in Microbiotashowed the presence of diverse, and mostly benign, microbial communities that were remarkably similar between hospitals and airplanes. The few pathogenic microbes, such as Escherichia coliwere in low densities and were not indicative of active infections. However, the 23 types of antibiotic resistance genes that appeared in both samples, linked to major classes of antibiotics like gentamycin and streptomycin, were grim evidence of the rise in antibiotic-resistant bacterial infections.

The 407 distinct microbes detected by a team of researchers led by Northwestern University scientists came largely from human skin. These included harmless bacteria, Staphylococcus epidermidis And Cutibacteria acnes. While the idea that we continually breathe in other people’s skin microbes is a little unsettling, it’s also to be expected.

Read more: »Why germs love our collective amnesia»

“Indoor air resembles indoor air, which also resembles human skin,” Northwest synthetic biologist and co-author Erica Hartmann said in a statement. As Hartmann and colleagues from the Harvard TH Chan School of Public Health and Argonne National Laboratory stated in the paper, humans naturally carry about 10¹² microorganisms on their skin, which spread through the air as we shed millions of skin cells per day.

Although airplane and hospital air teeming with harmless skin bacteria can be soothing or distressing, depending on who you ask, the methods the research team used to generate these results were undeniably ingenious. The scientists gathered data on disposable masks used by air travelers and healthcare professionals to learn more about indoor air quality at their study sites.

“We realized that we could use face masks as a simple and inexpensive air sampling device for personal exposures and general exposures,” Hartmann added.

The COVID-19 pandemic has inspired a wave of research into airborne microbes. But they are difficult to sample because air is a continually moving medium, carrying tiny, low-mass microbes such as viruses, bacteria and fungi. It’s like trying to sample moving needles in a haystack. Instead of directly assessing the airborne microbial community, researchers extracted microbes from face masks worn by people on airplanes or hospitals to assess microbial loads in these environments.

Using a “shotgun metagenomics” approach, Hartmann and colleagues extracted DNA from the exterior of 22 disposable masks. Travelers wore masks on domestic and international flights, while hospital staff wore masks for the duration of their shift and then mailed them in sterile bags to Harmann’s lab. Masks not worn served as study controls.

In addition to better characterizing the microbial environment in some of the places where humans congregate, the research has paved the way for repurposing face masks to study air quality in enclosed environments.

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Main image: Zubada / Shutterstock

• Devin Reese

  Published on December 4, 2025

  Devin Reese is the editor-in-chief of Natural history and a science writer based in Alexandria, Virginia.