Another Reason to Buy an Electric Car: Auto Exhaust Can Hurt Bees’ Ability to Find Food

Automotive exhaust makes us gag, so it may not come as a big surprise that it’s noxious to other critters. That’s a problem when it interferes with the ability of insects that pollinate our food to find food themselves.

A five-year study has determined that toluene, xylene, benzaldehyde, and other toxins emitted when vehicles burn gasoline disrupted moths’ sense of smell and capacity to find the flower of a plant, the Sacred Datura, that grows in Southwestern United States and northern Mexico.

“We tested a range of concentrations for these pollutants and found that even at relatively low intensities in semirural environments, it disrupted the moths’ abilities,” said Jeffrey Riffell, an assistant professor of biology at the University of Washington and the lead author of the study, which was recently published in the journal Science.

The implications of the findings aren’t restricted to moths. Bees and other pollinators may also be affected by automotive exhaust, according to Riffell.

“We’re interested to see if the same process might be potentially affecting the behavior of these other pollinators,” he said. “It could be that these pollutants are being transported away from these urban centers and affecting the agricultural areas.”

Scientists at the University of Southampton, in the U.K., reached a similar conclusion in a study published last year. The researchers taught honeybees in the laboratory to recognize a blend of floral scents. But when they added diesel exhaust to the mix, the bees lost their ability to detect many of those flower smells, even when the concentration of auto exhaust was within levels set for human health in the U.S. and Europe.

“Honeybees have a sensitive sense of smell and an exceptional ability to learn and memorize new odors, enabling them to use floral odors to help locate, identify, and recognize the flowers from which they forage,” the scientists wrote. “There is a huge diversity of floral odors; therefore any disruption to these blends could impact upon the ability of plants to communicate with their pollinators.”

In the U.S. study, Riffell’s team used a proton-transfer-reaction mass spectrometer to track the odors of the Sacred Datura’s white blossoms.

“The further we got away from the flower, we found that the local vegetation was swamping out the smell of the flower,” Riffell said. “So we decided to go into the laboratory, where we can control the odors and the odor backgrounds and re-create it in a more controlled way.”

Riffell and researchers at the University of Arizona decided to test toluene, xylene, and benzaldehyde after noting that their chemical structure was similar to those of the local vegetation that was causing the problem for the Manduca sexta moths.

The moths’ inability to smell the nectar of the Sacred Datura doesn’t mean that they’re going hungry. Riffell said that while he hasn’t studied whether auto exhaust has had an impact on moth numbers, moths do adapt—meaning that when the insects can’t find the flower they’re looking for, they learn to locate others.