But in recent years, an alarming number of bee colonies across North America and Europe have begun to collapse. As part of the phenomenon, formally known as Colony Collapse Disorder, worker bees fail to return to the hive after their pollen-collecting trips nearby. We still don’t fully understand what’s driving this trend, but the list of culprits likely includes pesticides, viral infections, intensive agriculture and perhaps even the practice of feeding bees high fructose corn syrup in place of the honey we take from them.

New research, though, suggests there may be an overlooked problem: the exhaust fumes produced by diesel-powered engines. As described in a study published today in Scientific Reports, a group of researchers from the UK’s University of Southampton found that the pollution produced by diesel combustion reduces bees’ ability to recognize the scent of various flowers—a key sense they use in navigating and finding food sources.