Notes from the Lab
Notes from the Lab – January 2024
Honey bees are experiencing unsustainable colony loss rates, and many species of wild pollinators are experiencing range contractions and population declines. Pesticides are not the only reason for these problems, but hundreds of scientific studies show very clearly they’re contributing.
For this and other reasons, some people think we should get rid of pesticides. But that’s not currently practical. Our largely monocultural agricultural system is susceptible to pests, and non-pesticide control measures are currently inadequate. So, the truth is we need pesticides to ensure the reliability of our food.
Because of this, there are many pesticide companies that produce many pesticides, they all have a financial incentive to sell as much product as possible, and they have many tactics to ensure those sales occur. But those are topics for another day.
The topic for today is the fact that all pesticides must pass through a risk assessment process before they’re registered and sold. In the USA, this process is overseen by the United States Environmental Protection Agency (EPA). This means all pesticides that are currently sold in the USA have passed the EPA’s risk assessment process.
But we know that pesticides are currently causing problems for pollinators. This means the current risk assessment process is inadequate. Perhaps this shouldn’t be surprising since the process isn’t very old. For example, the EPA is only 53 years old, and the tool the EPA uses to assess risk to bees — BeeREX — is only 8 years old. Indeed, when you download BeeREX from the internet, the file is called “BeeREX Version 1.0.”As with the first version of everything, there are kinks to work out.
So, what should go into “BeeREX Version 2.0”? What are the current shortcomings of the pesticide risk assessment process for bees, and how should those shortcomings be solved? These are the topics for the seventy-first Notes from the Lab, where I summarize “Breaking the cycle: Reforming pesticide regulation to protect pollinators,” written by Adrian Fisher and colleagues and published in the journal BioScience [2023].
The paper by Fisher and colleagues is an “ideas paper,” which means it doesn’t contain data. Instead, it contains references to lots of peer-reviewed literature highlighting problems within the current risk assessment process, and lots of ideas from the authors on how to improve the process. The Entomological Society of America provided support for the authors to initially meet and discuss common themes, then they wrote the paper.
So, what are the major problems with the current risk assessment process? The authors identify five major inadequacies of the current regulatory approach.
Overreliance on short-exposure laboratory lethality assays (i.e., LD50). Short-term LD50s are problematic because pollinators generally experience exposure to pesticides for much longer than a few days, and toxicity is well-known to increase with duration of exposure.
Failure to assess sublethal injurious effects on pollinators. Sublethal impacts on bee reproduction are particularly important due to the central role of reproduction in fitness and population change. Other sublethal effects, such as impacts on physiology and behavior, can also impact bee fitness.
Inadequate assessment of exposure. As a prime example, exposure to wind-blown dust from seeds coated with neonicotinoids was not estimated to be a major route of exposure when these pesticides were approved. In addition, after a pesticide is approved there is currently no requirement for real-world exposure data to be obtained (see Photos 1 & 2). Thus, there is no mechanism to assess whether predictions concerning exposure are actually borne out in the real world.
Overreliance on the western honey bee (Apis mellifera) as the model pollinator species. Apis mellifera lives in the largest colonies and is the most social of all ~20,000 bee species that exist in the world. Its colonies possess multiple social detoxification strategies that buffer impacts of pesticides. Because of this, it should not be surprising that numerous studies have found that other bee species, including stingless bees, bumble bees, and solitary bees, often experience more severe adverse impacts from pesticide exposure. This means a colony-level risk assessment approach using A. mellifera is not conservatively protective of pollinators.
Narrow focus on isolated active ingredients. Many pesticide formulations contain “inert ingredients” that are, in fact, toxic to bees. Moreover, pollinators are often exposed simultaneously to a diverse suite of pesticides that can have additive or interactive effects. The current risk assessment approach does not assess risk from “inert ingredients,” multiple-ingredient formulations, or co-exposures that commonly occur in the real world.
OK, these definitely seem like problems. Do other people agree these are problems? Yes. The most notable example is the European Food Safety Authority (EFSA), which is the European equivalent of the EPA. The EFSA recently updated their guidance on risk assessment for bees to address many of these problems (EFSA, 2023). Unfortunately, there are no current plans for an equivalent update at the EPA or other regulatory agencies.
If the EPA or other regulatory agencies decide to update their processes, what should they do? For each problem, the authors lay out proposed solutions. A visual representation of the proposed solutions is shown in Figure 1, where the current regulatory framework is shown on the left and the proposed framework is shown on the right. Note the current regulatory framework sometimes results in registered pesticides being banned, while the proposed framework avoids this shortfall of the current regulatory approach.
First, there should be greater realism in laboratory toxicity assays. For many non-pollinator model organisms, the short 48-hr LD50 approach is supplemented with additional endpoints and methods. These updated methods should be used for pollinators. For example, the new EFSA guidance recommends using the entire dose-response curve to extrapolate a no-observed-effect concentration, assessing time-reinforced toxicity, and assessing mixture toxicity (EFSA, 2023).
Technological advances have enabled scalable, cost-effective assays that assess synergistic impacts of pesticides on bees. One of these approaches, developed by Bayer scientists (Haas & Nauen, 2021), was highlighted in a previous Notes from the Lab column [see March 2021 column: 161(3):315-317]. Inexpensive lab-based approaches such as these, especially when developed and carried out by the pesticide companies themselves, can clearly be incorporated into the risk assessment process quite easily.
Perhaps most important, laboratory assessments of mortality should discard rigid timeframes, instead allowing the ….
