Air pollution is helping to drive a rise in antibiotic resistance that poses a significant threat to human health worldwide, a global study suggests.

The analysis, using data from more than 100 countries spanning nearly two decades, indicates that increased air pollution is linked with rising antibiotic resistance across every country and continent.

It also suggests the link between the two has strengthened over time, with increases in air pollution levels coinciding with larger rises in antibiotic resistance.

“Our analysis presents strong evidence that increasing levels of air pollution are associated with increased risk of antibiotic resistance,” researchers from China and the UK wrote. “This analysis is the first to show how air pollution affects antibiotic resistance globally.” Their findings are published in the Lancet Planetary Health journal.

Antibiotic resistance is one of the fastest-growing threats to global health. It can affect people of any age in any country and is already killing 1.3 million people a year, according to estimates.