Diesel Exhaust Has ‘Detrimental Effects’ On Honeybees, Can Disrupt Sense Of Smell

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Car exhaust may hamper honeybees’ sense of smell, a new study suggests.

Air pollutants emitted from diesel exhaust may interfere with the pollinators distinguishing floral odors, which can hurt their foraging efficiency, pollination and global food security.

“This could have serious detrimental effects on the number of honeybee colonies and pollination activity," Tracey Newman, a neuroscientist who worked on the study, said in a statement.

The findings, published in Scientific Reports, describes how a specific group of chemicals known as NOx diminish the honeybees’ ability to respond to floral scents. "This could have serious detrimental effects on the number of honeybee colonies and pollination activity," Newman said.

The team from Britain's University of Southampton made a mixture of eight chemicals from the scent of rapeseed flowers. When exposed to diesel exhaust, six out of the eight flowers had reduced chemicals, and two disappeared completely. Those that were mixed with fresh air were unaffected. The researchers then exposed the flowers to NOx gases, found in diesel exhaust, and found that the flower’s odor profile was altered.

"Honeybees have a sensitive sense of smell and an exceptional ability to learn and memorize new odors,” Newman said. “Our results suggest that that diesel exhaust pollution alters the components of a synthetic floral odor blend, which affects the honeybee's recognition of the odor.”

The team then used conditioned honeybees to see how affected they were by the flower’s changed odor. "Having trained a bunch of bees, we then tested to see if they would respond in the same way to the mixture that was depleted by exposure to NOx," Newman told the BBC.

The honeybees were less response to the flowers’ smell and did not stick out their tongues for pollination.

"A bee has far poorer recognition of an altered floral mix," Newman told LiveScience. "The bee needs to learn the unadulterated version, and if the bee has learned it, it will then struggle with the version that has been chemically altered."

Honeybees, one of the world’s leading pollinators that are responsible for an estimated $30 billion a year in crops, have been experiencing an alarming population decline in recent years. While the cause behind their falling numbers has yet to be determined, pesticides are often pointed to as the culprit, Reuters reports. The recent study may point to another factor: diesel air pollution, study author Professor Guy Poppy told LiveScience.

"Honeybee pollination can significantly increase the yield of crops and they are vital to the world's economy - £430 million a year to the UK alone,” Poppy said in a statement. “However to forage effectively they need to be able to learn and recognize the plants. Honeybees use the whole range of chemicals found in a floral blend to discriminate between different blends, and the results suggest that some chemicals in a blend may be more important than others."

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