Diesel pollution prevents honeybees from finding flowers

Photo: James Barker/freedigitalimages.net

Exposure to common air pollutants found in diesel exhaust pollution can affect the ability of honeybees to recognise floral odours, new University of Southampton research shows.

Honeybees use floral odours to help locate, identify and recognise the flowers from which they forage.

The Southampton team, led by Dr Tracey Newman and Professor Guy Poppy, found that diesel exhaust fumes change the profile of flora odour. They say that these changes may affect honeybees’ foraging efficiency and, ultimately, could affect pollination and thus global food security.

The study mixed eight chemicals found in the odour of oil rapeseed flowers with clean air and with air containing diesel exhaust. Six of the eight chemicals reduced (in volume) when mixed with the diesel exhaust air and two of them disappeared completely within a minute, meaning the profile of the chemical mix had completely changed. The odour that was mixed with the clean air was unaffected.

Furthermore, when the researchers used the same process with NOx gases (nitric oxide and nitrogen dioxide), which is found in diesel exhaust, they saw the same outcome, suggesting that NOx was a key facilitator in how and why the odour’s profile was altered. The changed chemical mix was then shown to honeybees, which could not recognise it.

Dr Newman, a neuroscientist at the University, comments: “Honeybees have a sensitive sense of smell and an exceptional ability to learn and memorize new odours. NOx gases represent some of the most reactive gases produced from diesel combustion and other fossil fuels, but the emissions limits for nitrogen dioxide are regularly exceeded, especially in urban areas. Our results suggest that that diesel exhaust pollution alters the components of a synthetic floral odour blend, which affects the honeybee’s recognition of the odour. This could have serious detrimental effects on the number of honeybee colonies and pollination activity.”

Professor Poppy, an ecologist at the University, adds: “Honeybee pollination can significantly increase the yield of crops and they are vital to the world’s economy... However to forage effectively they need to be able to learn and recognize the plants. The results indicate that NOx gases — particularly nitrogen dioxide — may be capable of disrupting the odour recognition process that honeybees rely on for locating floral food resources. 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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Protein explains increased asthma severity in children exposed to traffic pollution

A new study shows that exposure to diesel exhaust particles from traffic pollution leads to increased asthma severity in children. Moreover, the study finds that this is due to increased blood levels of IL-17A, a protein associated with several chronic inflammatory diseases, in children with high diesel exposure.

The study by researchers at Cincinnati Children's Hospital Medical Center is published online in the Journal of Allergy and Clinical Immunology.

The research, conducted in mice and in humans, showed that neutralizing IL-17A prevented airway inflammation. Neutralization of IL-17A "may be a useful potential therapeutic strategy to counteract the asthma-promoting effects of traffic-related air pollution, especially in highly exposed, severe allergic asthmatics," says Gurjit Khurana Hershey, MD, PhD, director of asthma research at Cincinnati Children's and senior author of the study.

Dr. Hershey and her colleagues studied 235 children and teens with asthma. The researchers plotted each person's primary address and estimated their diesel exposure attributable to traffic based on where they lived. The researchers also studied mice exposed to diesel particles and dust mites, a common household allergen.

In children with asthma, diesel exposure was associated with more frequent asthma symptoms and increased IL-17A blood levels. Similarly, exposure to both diesel and dust mites resulted in more severe asthma in mice compared to dust mite exposure alone. When IL-17A was neutralized in mice, it alleviated airway inflammation induced by diesel exposure.

"Blocking IL-17A may be a useful strategy to counteract the effects of traffic-related air pollution, especially in highly exposed allergic asthmatic children," says Dr. Hershey.
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