Honey is known to be the purest form of the extraction from the flowers by the hard work done by the bees.
Three quarters of the honeys 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 – 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.
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,” said 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.
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.
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 per cent).
“Throughout the world, bees are exposed to concentrations of neonics that have demonstrated effects on bees’ behaviour, physiology and reproductive abilities,” said Alexandre Aebi, lecturer in agroecology at the University of Neuchâtel and beekeeper.
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,” said Blaise Mulhauser, director of the botanical garden. “We selected priority honeys 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.