A global sampling of honey finds 75 percent of it to be contaminated with neonicotinoid pesticides according to a new research study. The good news is that the concentrations detected are below the amount authorized by the European Union for human consumption and safe to consume.
But for the bees themselves, situation is more bleak. Widespread application of neonicotinoids has been identified as a key factor responsible for the global decline in pollinators, particularly bees.
Edward A.D. Mitchell and his research team sought to explore the extent of exposure by testing 198 honey samples for five commonly used neonicotinoids: acetamiprid, clothianidin, imidacloprid, thiacloprid, and thiamethoxam. Samples were taken across all continents (except Antarctica), as well as numerous isolated islands. Overall, 75% of all honey samples contained at least one neonicotinoid; of these contaminated samples, 30% of contained a single neonicotinoid, 45% contained two or more, and 10% contained four or five. Concentrations were highest in European, North American, and Asian samples.
While the researchers emphasize that the concentrations of neonicotinoids were below levels that the EU authorizes in food and feed products, they do cite some emerging studies on the effects of neonicotinoids in vertebrates, such as impaired immune functioning and reduced growth, which may result in a re-evaluation of these restrictions.
As for the effects on bees, 34% of honey samples were found to have concentrations of neonicotinoids that are known to be detrimental. These results suggest that a substantial proportion of world pollinators are probably affected by neonicotinoids.
Neonicotinoids harmful to bees
In a separate study, biologists at the University of California San Diego demonstrated that these widely used neonicotinoid pesticides can significantly impair the ability of otherwise healthy honey bees to fly, raising concerns about how pesticides affect their capacity to pollinate and the long-term effects on the health of honey bee colonies.
Previous research has shown that foraging honey bees that ingested neonicotinoid pesticides, crop insecticides that are commonly used in agriculture, were less likely to return to their home nest, leading to a decrease in foragers.
Months of testing and data acquisition revealed that typical levels of neonicotinoid exposure, which bees could experience when foraging on agricultural crops–but below lethal levels — resulted in substantial damage to the honey bee’s ability to fly.
“Our results provide the first demonstration that field-realistic exposure to this pesticide alone, in otherwise healthy colonies, can alter the ability of bees to fly, specifically impairing flight distance, duration and velocity” said Tosi. “Honey bee survival depends on its ability to fly, because that’s the only way they can collect food. Their flight ability is also crucial to guarantee crop and wild plant pollination.”
Long-term exposure to the pesticide over one to two days reduced the ability of bees to fly. Short-term exposure briefly increased their activity levels. Bees flew farther, but based upon other studies, more erratically.
“Bees that fly more erratically for greater distances may decrease their probability of returning home,” said Nieh, a professor in UC San Diego’s Division of Biological Sciences.
This pesticide does not normally kill bees immediately. It has a more subtle effect, said Nieh.
“The honey bee is a highly social organism, so the behavior of thousands of bees are essential for the survival of the colony,” said Nieh.” We’ve shown that a sub-lethal dose may lead to a lethal effect on the entire colony.”
Honey bees carry out fundamentally vital roles in nature by providing essential ecosystem functions, including global pollination of crops and native plants. Declines in managed honey bee populations have raised concerns about future impacts on the environment, food security and human welfare.
Neonicotinoid insecticides are neurotoxic and used around the world on broad varieties of crops, including common fruits and vegetables, through spray, soil and seed applications. Evidence of these insecticides has been found in the nectar, pollen and water that honey bees collect.
“People are concerned about honey bees and their health being impaired because they are so closely tied to human diet and nutrition,” said Nieh. “Some of the most nutritious foods that we need to consume as humans are bee-pollinated.”
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