Thursday, November 9, 2017

Neonicotinoids in Honey

In a recent study published in Science, Mitchell et al found that most honey sampled from around the world between 2012 and 2016 contained neonicotinoid pesticides at levels known to be neuroactive to bees. Neonicotinoid are currently the most widely used class of pesticides worldwide. The neonicotinoids are taken up by plants and contaminate the pollen and nectar. Neonicotinoids have been identified or suspected as a key factor responsible for the decline in bees.

During the winter of 2006-2007, a large number of bee colonies died out, losses at the impacted beekeeping operations were reported to be from 30% to 90%. While many of the colonies lost during this time period exhibited the symptoms from parasitic mites, many were lost, from unknown cause. The next winter, the number of impacted honey bee operations spread across the country. The phenomenon was termed Colony Collapse Disorder.

Over the past decade Colony Collapse Disorder has spread around the world. In 2012, 31% of the U.S. honey bee colonies were wiped out. The year before that it was reported as 21% of colonies lost. These losses if they continue could have a catastrophic impact on agriculture. One third of all food eaten in the United States requires honey bee pollination.

Recent field studies published this year in Science have found widespread contamination of agricultural land worldwide by neonicotinoid pesticides. These findings suggest that chronic low level exposure to neonicotinoids may be impacting bee colonies. Currently pesticide safety testing focuses on acute exposure risk not extremely low levels of chronic exposure. Neonicotinoids work by targeting the nicotinic acetylcholine receptors in the insect brain which are responsible for learning and memory. Acute activation of theses receptors by neonicotinoids causes seizure then neuron non-response.

During experiments carried out by Piroinen et al in 2016 it was found that low level neonicotinoid exposure causes neural dysfunction that limits a bee’s capacity to learn and remember. Chronic exposure resulted in reduced foraging ability (Gill et al 2012) and poor colony growth (Moffat et al 2015, 2016) and is believed to be a factor in Colony Collapse Disorder.

The vast majority of plants are pollinated by insects, and bees are responsible for the vast majority of pollination. Commercial agriculture uses honey bees raised to pollinate its crops. A Cornell University study estimates that the value of honey bee pollination in the United States is more than $14.6 billion annually.

In the current study, Dr. Mitchell found neonicotinoids in 75% of 198 honey samples collected from honey producers. In North America 86% of the samples had neonicotinoids detected. The concentrations found in honey are below the maximum residue level allowed for human consumption, but within the bioactive range for honey bees.

Although recording of pesticide use is required in the European Union and the United States (under the 1990 Farm Bill), it is not collected into a searchable database that would allow the finding of statistical correlation of pesticides used with human chronic diseases or ecosystem damage. Chronic low level exposure may be more damaging than we ever imagined. It is time to reexamine our assumptions and develop methods to measure impact from chronic low level exposure.

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