Edward Mitchell, a scientist with the University of Neuchatel in Switzerland, published a paper in Science detailing the extent to which trace amounts of neonicotinoids, an insecticide that acts on the nervous systems of insects and which have been linked to the steep decline in bee populations across the globe, shows up in honey.
The concentrations detected by the researchers over the course of the study are below levels authorized by the European Union for human consumption, but don’t bode well for pollinators and bees.
Neonicotinoids, from the same chemical family as nicotine, represent some of the most common insecticides used on earth. Their widespread application has been identified in numerous scientific studies as the key factor in the steep decline of all pollinators, particularly bees.
The pesticides are believed to be a large contributor to honey-bee colony collapse disorder, where the majority of worker bees inexplicably abandon a hive, leaving the queen, a substantial amount of honey and a few nurse bees that care for the queen and immature bees.
The phenomenon affects not only agriculture, where bees are needed to pollinate crops, but also the food web, as steep declines in bird populations have been linked to the disappearance of bees and other insects.
Mitchell and his colleagues set out to study the extent of insecticide exposure by testing 198 samples of honey from spots all over the globe. They looked for traces of five of the most commonly used neonicotinoids: acetamiprid, clothianidin, imidacloprid, thiacloprid and thiamethoxam.
The samples were taken from all continents except Antarctica, along with several isolated islands.
Only 25 percent of the samples were free of any trace amounts of neonicotinoids.
Of the 75 percent that were contaminated with pesticides, 30 percent contained trace amounts of a single neonicotinoid, while 45 percent had two or three insecticides and 10 percent contained four or five.
Europe, Asia and North America saw the highest thresholds of insecticides in honey samples, while South America, Australia and Africa had relatively low exposure rates.
While the authors are quick to note the exposure levels are below what is currently deemed safe for human consumption, they expressed concern over new studies that show vertebrates suffer health effects from exposure to the family of insecticides, including impaired immune systems and growth reductions, meaning that health officials may soon re-evaluate exposure thresholds.
The European Union took steps to restrict the use of certain neonicotinoids in 2013.
Regarding bees, the study shows that 34 percent of the nearly 200 samples contained insecticide levels known to be detrimental to bees and other pollinators, demonstrating that a substantial portion of the global population of pollinators are adversely affected by the widespread distribution of neonicotinoids.