Air pollution could be hazardous in more ways that previously thought. Scientists in Gothenburg, Sweden have found that polluted air is a possible means of transmitting drug-resistant bacteria.

A team of researchers demonstrated that air samples from Beijing contain DNA from genes that make bacteria resistant to the most powerful antibiotics available for treatment. The scientists looked for such genes in 864 samples collected from humans, animals, and different environments across the world.

The study, published in the journal Microbiome on November 18, found that water, sediment, and soil carried lesser antibiotic-resistant genes and fewer varieties of them, while waste water or sludge had high levels and more varieties of such genes. The highest abundance and diversity of antibiotic-resistant genes, including those resistant to powerful antibiotics, was found in industrial air pollution, the affluents disposed of by pharmaceutical industries and air samples from a Beijing smog event.

“We studied only a small number of air samples, so to generalise, we need to examine the air from more places,” said Joakim Larsson, director of the Centre for Antibiotic Resistance Research at the University of Gothenburg in a press release. “But the air samples we did analyse showed a wide mix of different resistance genes. Of particular concern is that we found a series of genes that provide resistance to carbapenems, a group of last resort antibiotics taken for infections caused by bacteria that are often very difficult to treat.”

The press release said the study does not show whether the sampled bacteria were actually alive in the air, which would make them a real threat. “It is reasonable to believe that there is a mixture of live and dead bacteria, based on experience from other studies of air,” said Larsson.

Also part of the research team were Chandan Pal, Johan Bengtsson-Palme and Erik Kristiansson.