Evidence suggests that particulate matter PM2.5 can contain antibiotic-resistant bacteria and resistance genes, which may be transferred between environments and inhaled directly by humans, the authors said.

Long-term exposure to air pollution is associated with chronic conditions such as heart disease, asthma and lung cancer, reducing life expectancy.

Short-term exposure to high pollution levels can cause coughing, wheezing and asthma attacks, and is leading to increased hospital and GP attendances worldwide.

The lead author, Prof Hong Chen of Zhejiang University in China, said: “Antibiotic resistance and air pollution are each in their own right among the greatest threats to global health.

Until now, there was limited data on how much influence PM2.5 air pollution – which is made up of particles 30 times smaller than the width of a human hair – has on antibiotic resistance globally.