Until now, microorganisms had been studied in our bodies, on surfaces, in soil, water, air… but not in air from really high altitudes. Now, a research team from the Barcelona Institute for Global Health (ISGlobal) has conducted the first study in which samples from the troposphere were taken to analyze their microorganism content and trace their journey.
The air rising from mainland China moves towards Japan, where it descends over the city of Tokyo due to the winter weather conditions. These air currents were precisely the paths the researchers followed to collect up to 22 aerosol filter samples.
Subsequent analysis reveals that there are more than 570 different genera of microorganisms, including fungi and bacteria. These are associated with aerosols, often accompanied by zinc sulfate and potassium, substances used as fertilizers and pesticides. This suggests an agricultural origin, typical of northeastern China, and means they are capable of traveling more than 2,000 kilometers through the air.
Among the identified microorganisms, the authors found viable pathogens, capable of infecting and potentially causing diseases in susceptible and immunocompromised people. Additionally, some of the bacteria showed resistance to common antibiotics. This suggests that resistance could spread over long distances, something that was previously unknown.
The air samples taken at 1,000 and 3,000 meters altitude yielded similar results to soil samples from the city of Chōfu, near Tokyo. This comparison shows that air descends from high altitudes to the surface, a phenomenon simulated by models created by Roger Curcoll, a researcher from BarcelonaTech-UPC.
Xavier Rodó, first author of the article, explains that certain materials can travel long distances through the air because, at higher altitudes, there is less friction with the surface. What this study has now discovered, through international collaborations, is that microorganisms can also travel at high altitudes and, despite harsh conditions, they can remain viable. “These data represent a paradigm shift in our understanding of how human health can be affected by pathogens that thrive in the environment, especially in the air,” says Rodó, highlighting the need for further research on the long-distance spread of pathogenic microorganisms.
Rodó, X., Pozdniakova, S., Borràs, S., Matsuki, A., Tanimoto, H., Armengol, M.P., Pey, I., Vila, J., Muñoz, L., Santamaria, S., Cañas, L., Morgui, J.A., Fontal, A., Curcoll, R. (2024). Microbial richness and air chemistry in aerosols above the PBL confirm 2000-km long-distance transport of potential human pathogens. PNAS. doi:10/1073/pnas.2404191121.
