Just as the bustling holiday travel period approaches, researchers are sharing findings on a question frequently on people’s minds as they board crowded aircraft: What is the true cleanliness of airplane air?
To investigate this, Erica Hartmann, an associate professor in Northwestern University’s department of civil and environmental engineering, along with her team, analyzed face masks worn by passengers on flights to document the types of microbes these items captured. The team also focused on the air in hospitals, another public setting where germs commonly spread, by testing face masks used by hospital staff.
The team collected 53 masks in sterile bags and carefully removed their outer layers to specifically analyze airborne microbes, distinct from those in people’s respiratory passages. They then extracted and analyzed DNA from these samples. To guarantee comprehensive detection of all microbial DNA present, they also utilized PCR, an amplification process, to enrich the genetic material found on the masks.
Overall, as reported in the journal Microbiome, they identified 407 microbial species from both airplane and hospital settings, with similar populations of microorganisms in each. Hartmann stated that the vast majority of these originated from human skin and are harmless. “This isn’t surprising, because many of the microbes found in buildings and the air around us are a reflection of ourselves,” she explained. “Numerous surfaces we touch tend to harbor skin-associated microbes because we transfer them every time we make contact. We disperse microbes wherever we go—my colleagues and I refer to this phenomenon as a microbial aura.”
The kits employed by the team for extracting genetic material from microbes were designed to gather DNA, meaning the researchers predominantly captured bacteria, not viruses, many of which are RNA-based (such as COVID-19 and influenza). While individuals might be more concerned about the amount of virus circulating in a confined space like an aircraft cabin, Hartmann suggests that viruses likely constitute a smaller proportion of airborne microbes than bacteria, since people shed greater quantities of skin bacteria than they release viral particles.
She noted that viruses typically depend heavily on the appropriate environment to thrive, and once outside the body and away from infectable cells, their virulence can diminish somewhat—though there are numerous examples of viruses surviving on surfaces, and studies indicate that only a small viral load is needed to infect someone and cause illness.
The study’s outcomes underscore the importance of developing improved methods for monitoring airborne pathogens, including viruses, through filtration and sensing systems capable of providing more real-time data. “Imagine a system similar to a carbon monoxide detector or a gas alarm that, depending on the detected levels of microbes, could automatically increase air exchange rates or notify people to put on masks,” Hartmann proposed. “Incorporating health considerations and enabling informed decisions about self-protection would be transformative.”
Until such systems are widespread, Hartmann hopes people will remember that as colder weather arrives and indoor gatherings become more frequent, the air—even in enclosed spaces like planes or hospitals—might not be as saturated with disease-causing germs as commonly believed. Another key lesson is that face masks offer an effective means of protection against pathogens that may be circulating in the air (and also prevent you from transmitting germs to others if you are unwell).
