Barcelona Institute for Global Health

By Douglas Main

A wide variety of fungi and bacteria, including E. coli and other potential human pathogens, have been found high in the atmosphere where they can travel for hundreds to thousands of miles before falling back to Earth, according to new research.

Air samples collected from between roughly a half mile and two miles in altitude (1 kilometer to 3 kilometers) near Tokyo, Japan, carried bacterial species known to be capable of causing health problems such as food poisoning and skin infections, researchers said.

The study, published this week in Proceedings of the National Academy of Sciences, reported that while most of the microbes detected were likely dead, testing confirmed more than ten species of microbes collected from high in the sky were alive. Those were particularly hardy strains, including several found to be antibiotic resistant. One of these, a type of ubiquitous bacteria not known to normally infect humans, was resistant to five different antibiotic drugs.

The discovery represents a “paradigm shift,” said Xavier Rodó, the study’s lead author and head of the health and climate program at the Barcelona Institute for Global Health. “From the public health standpoint it opens the door to really viewing the air and the atmosphere as an environment we need to pay attention to.”

The scientists used atmospheric measurements and computer models in concluding that most of the material found over Tokyo was coming from an agricultural region in northeast China, where row crops and livestock are raised. The study authors hypothesized that some of the bacteria, including the antibiotic-resistant ones, derived from sewage used to fertilize the land, and from the soil itself.

Widespread use of antibiotics with industrialized livestock production could plausibly introduce antibiotic resistance bacteria into the atmosphere as bits of soil and manure can be aerosolized and blow away on the wind, said David Smith, a NASA microbiologist who wasn’t involved in the study.

Besides microbes, the researchers also found significant quantities of many elements normally found in soil, such as sulfur and sodium, as well as aluminum, potassium, iron, and calcium.

They also detected zinc sulfate nanoparticles, which they hypothesized are coming from fertilizer use, as well as trace quantities of zirconium and hafnium, metals mined in China but not in Japan.