From the University of Maryland, a 2016 study focussing on the honeybee colonies’ exposome, a term traditionally used in cancer research. It’s defined as the measure of all exposures over an individual’s lifetime and how those exposures relate to health. In their investigation, researchers did not look at individual honeybees but instead treated the colony as a single super-organism basing its results on lifetime exposure to agricultural chemicals. Simply put, these models attempted to summarize potential risk from multiple contaminations in real-world contexts.
Researchers gauged the effect of pesticide exposure not only by looking at the number of pesticides in colonies, but also their toxicological relevance over a specific threshold, as well as through the calculation of a hazard quotient (HQ), which evaluates the cumulative toxicity of various pesticide residues.
Pesticide detections and HQ spiked when colonies were placed in agricultural fields for pollination (including blueberry, apple, citrus and cucumber production), and decreased when placed in a holding yard or put into honey production.
The 91 honey bee colonies studied were exposed to a total of 93 different pesticide compounds throughout the course of their pollination season. Of these residues, 13 different compounds were found in bees, 61 in beebread (packed pollen within the hive), and 70 were found in wax.
Pesticide load and hazard were also elevated in colonies that experienced a queen event —when a queen is replaced, in the process of being replaced, or queenless. A queen event is a predictor that a colony will die-off within ~50 days. Researchers found levels of synthetic pyrethroids were higher in colonies with a queen event, echoing past research showing adverse effects to bee reproduction from pyrethroid exposure. While scientists did not find a significant contribution from neonicotinoids, a class of chemicals widely implicated in bee and other pollinator declines, co-authors of the research note the study may not have been set up to adequately investigate their impact.
The implications of this research stretch beyond a single class of chemicals. While the body of science on neonicotinoids, including EPA’s own determination that these chemicals are highly toxic to bees, indicates that they should be immediately removed from use, it is evident that chemcial-intensive agriculture in general is owed much of the blame. Rather than focus on reducing pesticide exposure or refraining from use when bees are present, agrichemical companies, the conventional farming community, and federal regulators must take a long look at what practices are truly sustainable in the long term. It is clear that insect pollination and its subsequent health and economic benefits will not be maintained if measures aren’t taken to drastically shift agricultural production toward safer practices modeled on organic agriculture. By focusing on soil health, biodiversity, cultural practices like crop rotation and intercropping, and limited off-farm inputs, organic systems represent a viable, scalable path forward.
Related Links
University of Maryland – Study High Number of Pesticides Within Colonies Linked to Honey Bee Deaths
https://cmns.umd.edu/news-events/features/3628
In-hive Pesticide Exposome: Assessing risks to migratory honey bees from in-hive pesticide contamination in the Eastern United States
http://www.nature.com/articles/srep33207