High concentrations of neonics has been found in honeys from North America, Asia and Europe, according to a study published in the leading scientific journal Science by an interdisciplinary team from the University of Neuchâtel and the Botanical Garden of Neuchâtel, Switzerland. Three-quarters of the honey produced throughout the world contain neonicotinoids (neonics) – a class of pesticides known for their role in the decline of bees and for their harm to a large number of non-target species. The measured concentrations of neonics are, however, below the maximum authorized levels for human consumption.
“Based on this latest science, the large majority of studied samples do not represent any health risk for consumers,” says the study’s lead author, Edward Mitchell, professor and head of the laboratory of soil biodiversity at the University of Neuchâtel (currently on sabbatical at Landcare Research in Lincoln, New Zealand).
The situation is more critical, however, for bees.
“Throughout the world, bees are exposed to concentrations of neonics that have demonstrated effects on bees’ behavior, physiology and reproductive abilities,” said Alexandre Aebi, lecturer in agroecology at the University of Neuchâtel and beekeeper.
Neonics account for one-third of the global pesticide market. They are used to protect major crops such as corn and soy from pest insects. Neonics attack the central nervous system of invertebrate pests, causing paralysis and death. Because neonics are found throughout the plant, including the pollen and nectar, bees are contaminated when they forage – resulting in contaminated honey.
Aebi reveals this study is indeed a global worry. “We found that 75 percent of our honey samples are contaminated by neonicotinoids. The next step is to evaluate the concentration at a regional scale to be able to link neonicotinoid concentrations with difficulties encountered by beekeepers and agricultural practices. We also wish to fulfill other research gaps such as the impact of neonicotinoids on solid biodiversity.”
“In this study, we analyzed about 50 scientific papers documenting negative effects of those molecules on bees and other beneficial insects, at concentrations in the range of the concentrations we found in our study,” he explains. “We can then say that bees and other beneficial insects are most likely negatively affected by neonicotinoids throughout the world.”
“The concentration of neonicotinoids we found (on average 1.8ng/g are well below the maximum residues levels authorized for these molecules (50ng/g for acetamiprid, imidacloprid and thiacloprid and 10ng/g for clothianidin and thiamethoxam). It is then absolutely not dangerous to consume this honey,” he confirms.
“I am not sure we should regulate the levels of pesticides,” Aebi notes. “Given the impact, these molecules have on honeybees and other beneficial insects, we should follow France’s example and ban them.”
Conducted in 2015 and 2016, the study analyzed 198 honey samples from around the world, looking for the five most commonly used neonics: acetamiprid, clothianidin, imidacloprid, thiacloprid and thiamethoxam.
Seventy-five percent of the honey samples contained at least one of the five tested substances. The proportions varied considerably among regions, with the highest levels in North America (86 percent), Asia (80 percent) and Europe (79 percent), and the lowest in South America (57 percent). Oceania, New Zealand and the Pacific Islands were slightly below average (71 percent).
“We are able to quantify these molecules with excellent precision, at concentrations of one per 10 billion (0.1 ppb) or less,” says Gaétan Glauser, the head of the analytical platform.
Thirty percent of all samples contained a single neonicotinoid, 45 percent contained between two and five, and 10 percent contained four or five. Measured concentrations were below the maximum residue level authorized for human consumption for all compounds and samples, but total concentration exceeded this limit for two samples containing five neonicotinoids. It remains to be determined how contamination by multiple substances (the “cocktail effect”) may affect bees, humans or other organisms.
The researchers used a worldwide collection of honey obtained through a citizen science effort led by the botanical garden of Neuchâtel.
“The samples were randomly provided by more than 100 donors,” explains Blaise Mulhauser, director of the botanical garden. “We selected priority kinds of honey from small and local producers, in order to obtain a balanced geographical representation.”
The research was made possible by the Neuchâtel Platform of Analytical Chemistry (NPAC) at the University of Neuchâtel, where the analytical tools detect trace concentrations of neonics in complex matrices, such as honey.
Prof. Mitchell is also a member of the International Task Force on Systemic Pesticides, which released the second installment of its Worldwide Integrated Assessment of the Effects of Systemic Pesticides on Biodiversity and Ecosystems in Ottawa, Canada, last week. The peer-reviewed study will be published in an upcoming edition of Environmental Science and Pollution Research.
