Diesel Exhaust Inhibits Bees' Sense of Smell, New Study Says

Scientific Reports says diesel exhaust, emitted from truck engines and car engines, is responsible for creating air pollutants that hamper honeybees' ability to recognize and identify the scent of flowers.

For honeybees to forage for flowers -- to hunt, to pursue and index individual floral scents -- it is important that flowers retain their unique aroma, each flower comprised of an exclusive chemical makeup. If bees are not able to decipher smells, they will be unable to return to their hives and properly demonstrate their "waggle dance," a ritualistic dance that communicates their findings to the other bees. The result of them, and companion bees, not being to discriminate between different flowers would mean that couldn't attain proper resources, or pollinate.

NOx gases -- particularly nitrogen dioxide -- degrade particular chemicals of floral odors and eliminate preexistent olfactory markings. NOx gases are the sole component of diesel exhaust that is to blame for the degradation of floral odors, because it carries both nitrogen and oxygen. NOx gases initiate chemical change in flowers, and confuse bees' sensitive sense of smell -- which usually is able to understand the 1,000 different chemicals that make each flower odor distinct.

Urban environments almost ensure the failure of hives because of increased traffic and mobile emissions of diesel exhaust which damage floral odors. This is in addition to other stresses, like insecticides and diseases. Smog or ground-level ozone and ultraviolet (UV) radiation also play a role in the degradation of the floral mix.

Britain's University of Southampton team members, led by Tracey Newman and Guy Poppy, conducted an experiment with rapeseed flowers, exposing them to a blend of eight chemicals. The result of the experiments was the chemical reduction of the scents of six of the flowers, and complete chemical deterioration of the flowers' odor profile in two others.

Honeybees are one of world's leading pollinators, alongside beetles, butterflies and birds, and they add a stunning $203 billion annually to the human economy, according to a 2011 U.N. report. So bees' increased loss of scent recognition (in combination with other stresses) will not only cause a ripple in the global economy and cause a reduction in the pollination of flowering plants -- including fruit and vegetable crops -- but it will encourage the steady decline of the bee population.