75 Percent of Global Honey Samples Are Contaminated by Neonicotinoid Pesticides

From the Amazonian rainforest to the mountains of Switzerland, bees are blending poison into their sweet honey.

Neonicotinoids, the neurotoxins common in pesticides, tainted around three-quarters of approximately 200 honey samples from around the world, researchers reported today in the journal Science.

“I purchased honey from an Indian chief when I was visiting central Brazil,” said Edward Mitchell, a biologist at the University of Neuchâtel in Switzerland. “I thought, ‘I’m buying this from an Indian. It will be pure honey.’ Guess what? It has pesticides.”

The findings don’t necessarily reveal the primary cause of colony collapse disorder — when worker bees leave their hive empty and don’t return — but they provide insight into yet another environmental factor that is putting stress on the pollinators that are crucial to the food chain.

“I’m happy to accept is multifactorial,” said Mitchell, referring to theories that colony collapse has many causes. “But if there is one factor we don’t need, it’s this one.”

Thirty percent of the honey sampled had one kind of neonicotinoids of the five commonly used in agriculture and gardening that Mitchell and his colleagues tested: acetamiprid, clothianidin, imidacloprid, thiacloprid, and thiamethoxam. Forty-five percent contained two or more. Ten percent contained four or five kinds of pesticides.

And 34 percent of the honey samples had concentrations known to be harmful to bees, including lowering reproduction rates and disorienting the critters so they can’t find their way back to their hives after they’ve found nectar.

Mitchell and his colleagues thought of surveying the honey after, without any purpose in mind, they’d amassed a collection of samples at the Neuchâtel Botanical Garden. They had compiled around 300 jars of honey whose origins and ingredients they knew based on labels and firsthand experiences like Mitchell’s in Brazil. They then chose samples from every continent but Antarctica to reflect the geographic diversity of the planet.

“We asked people to bring honey that was of specific origins, not just mixed honey,” he said. “We said, ‘This is something useful and precious.’”

Study co-author Alexandre Aebi contributed honey from his personal hive kept in an oak forest in the hills above Neuchâtel. Neither Aebi nor farmers nearby use neonicotinoids but people in the city must be spraying them, said Mitchell.

“People are planting flowers. They are buying flowers in garden centers. These flowers are loaded with pesticides,” he said. “For human consumption, we have very strict rules. There are no such things for garden centers.”

The fact that most honey contained toxins, even when it was produced in the most remote locations where beekeepers never use pesticides or nonorganic materials, was disheartening, said Mitchell.

“I’ve grown up hearing about enviro damage, the ozone depletion, whales dying, rhinos, everything,” he said. “We have become accustomed to this. This for me has been a wakeup call.”

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Governments needed to mandate agricultural techniques and other policies so that societies could phase out the pesticides, he said.

After banning some but not all neonicotinoids in 2013, the European Union is now considering tougher restrictions, including potentially a moratorium on their use.

In the United States, the Environmental Protection Agency has admitted that neonicotinoids could be hurting bees and has drafted rules on how to keep using them while minimizing harm to the insects.

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