Researchers from the universities of Southampton and Reading suggest that toxic nitrous oxide (NOx) in diesel exhausts could be having an even greater effect on bees’ ability to smell out flowers than was previously thought.

NOx is a poisonous pollutant which is given off by diesel engines and which is harmful to humans. It has also previously been shown to confuse bees’ sense of smell, which they rely on to sniff out their food.

The study found that there is now evidence to show that, of the 11 most common single compounds in floral odours, five have can be chemically altered by exposure to NOx gases from exhaust fumes.

Lead author Dr Robbie Girling, from the University of Reading’s Centre for Agri-Environmental Research, said: “Bees are worth millions to the British economy alone, but we know they have been in decline worldwide.

“We don’t think that air pollution from diesel vehicles is the main reason for this decline, but our latest work suggests that it may have a worse effect on the flower odours needed by bees than we initially thought.

“People rely on bees and pollinating insects for a large proportion of our food.”