Effect of Insecticide Exposure Across Multiple Generations of the Earthworm Eisenia andrei

The toxicity of neonicotinoids and many of their replacement insecticides to nontarget soil invertebrates such as earthworms has previously been established. However, the long-term effects of these substances on these organisms are largely unknown. In the field of soil ecotoxicology, lumbricid earthworms such as Eisenia andrei are used extensively due to the availability of standardized test methods and their adaptability to laboratory culture and testing. Multigenerational studies have gained popularity and attention in recent years, with a shift toward the use of long-term assays and lower concentrations of test chemicals. The use of exposure concentrations that include those measured in a monitoring program carried out by the Government of Ontario presents a realistic exposure scenario that may not show significant effects in contemporary, shorter term studies. We used current standardized test methods as a basis for the development of multigenerational studies on E. andrei. The effects of exposure to a single application of the insecticides thiamethoxam and cyantraniliprole on the survival and reproduction of E. andrei were observed over three (thiamethoxam) or two (cyantraniliprole) generations using consecutive reproduction tests. No significant impacts on adult survival were reported in any generation for either insecticide, whereas reproduction decreased between the first and second generations in the thiamethoxam test, with median effective concentration (EC50) values of 0.022 mg/kg dry weight reported for the first generation compared with 0.002 mg/kg dry weight in the second generation. For cyantraniliprole, an EC50 of 0.064 was determined for the first generation compared with 0.016 mg/kg dry weight in the second generation. A third generation was completed for the thiamethoxam test, and a significant decrease in reproduction was observed in all treatments and controls compared with previous generations. No significant difference between thiamethoxam treatments and the control treatment was reported for the third generation. Collectively, these data indicate that exposure of oligochaetes to these two insecticides at concentrations representative of field conditions may result in long-term stresses. Environ Toxicol Chem 2024;00:1-13. © 2024 The Author(s). Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Low doses of the organic insecticide spinosad trigger lysosomal defects, elevated ROS, lipid dysregulation, and neurodegeneration in flies

Large-scale insecticide application is a primary weapon in the control of insect pests in agriculture. However, a growing body of evidence indicates that it is contributing to the global decline in population sizes of many beneficial insect species. Spinosad emerged as an organic alternative to synthetic insecticides and is considered less harmful to beneficial insects, yet its mode of action remains unclear. Using Drosophila, we show that low doses of spinosad antagonize its neuronal target, the nicotinic acetylcholine receptor subunit alpha 6 (nAChRα6), reducing the cholinergic response. We show that the nAChRα6 receptors are transported to lysosomes that become enlarged and increase in number upon low doses of spinosad treatment. Lysosomal dysfunction is associated with mitochondrial stress and elevated levels of reactive oxygen species (ROS) in the central nervous system where nAChRα6 is broadly expressed. ROS disturb lipid storage in metabolic tissues in an nAChRα6-dependent manner. Spinosad toxicity is ameliorated with the antioxidant N-acetylcysteine amide. Chronic exposure of adult virgin females to low doses of spinosad leads to mitochondrial defects, severe neurodegeneration, and blindness. These deleterious effects of low-dose exposures warrant rigorous investigation of its impacts on beneficial insects.

Chemical pollution: A growing peril and potential catastrophic risk to humanity

Anthropogenic chemical pollution has the potential to pose one of the largest environmental threats to humanity, but global understanding of the issue remains fragmented. This article presents a comprehensive perspective of the threat of chemical pollution to humanity, emphasising male fertility, cognitive health and food security. There are serious gaps in our understanding of the scale of the threat and the risks posed by the dispersal, mixture and recombination of chemicals in the wider environment. Although some pollution control measures exist they are often not being adopted at the rate needed to avoid chronic and acute effects on human health now and in coming decades. There is an urgent need for enhanced global awareness and scientific scrutiny of the overall scale of risk posed by chemical usage, dispersal and disposal.

Potential Environmental Health Risk Analysis of Neonicotinoids and a Synergist

The extensive use of neonicotinoid pesticides has led to their widespread presence in the environment, resulting in considerable safety risks to the ecosystem and human health. In this study, we investigated the biotransformation behavior of a cocktail of multiple neonicotinoids and piperonyl butoxide (PBO) synergist in vivo and their potential environmental health risk. It was found that neonicotinoids with a cyano group, such as acetamiprid and thiacloprid, tended to accumulate in liver and spleen tissues, while others with nitro groups (imidacloprid, thiamethoxam, clothianidin, dinotefuran, and nitenpyram) were mostly excreted in urine. In the presence of the synergist PBO, the metabolism of neonicotinoids in vivo changed, mainly through the nitro reduction pathway, while a low abundance of related metabolites was observed in the conventional hydroxylation and demethylation metabolic pathways, due to inhibition of CYP450 enzymes by the synergist. Furthermore, DNA methylation damage in vivo was exacerbated by the induction of hydroxylamine metabolites formed in the intermediate process of neonicotinoid metabolism with the synergistic effect of PBO, which resulted in a higher level of the O⁶-methyldeoxyguanosine (O⁶-medG) biomarker in the liver. Therefore, during the comprehensive evaluation of pesticide environmental risks, attention should be paid not only to the co-exposure mode under real environmental conditions but also to the potential risks of intermediate metabolism and related intermediate metabolites. This study provides a referential strategy and theoretical support for the health risk assessment of co-exposure of chemicals.

Long-term dynamics of honey bee colonies following exposure to chemical stress

Pesticide residues have been linked to reduced bee health and increased honey bee colony failure. Most research to date has investigated the role of pesticides on individual honey bees, and it is still unclear how trace levels of pesticides change colony viability and productivity over seasonal time scales. To address this question we exposed standard bee colonies to chemical stressors known to have negative effects on individual bees, and measured the productivity of bee colonies across a whole year in two environments: near Tucson Arizona and Sydney Australia. We exposed hives to a trace amount of the neonicotinoid imidacloprid and to the acaricide thymol, and measured capped brood, bee and honey production, as well as the temperature and foraging force of the colonies. The effect of imidacloprid on colony dynamics differed between the two environments. In Tucson we recorded a positive effect of imidacloprid treatment on bee and brood numbers. Thymol was associated with short-term negative effects on bee numbers at both locations, and may have affected colony survival at one location. The overall benefits of thymol for the colonies were unclear. We conclude that long-term and colony-level measures of the effects of agrochemicals are needed to properly understand risks to bees.

Traces of a Neonicotinoid Induce Precocious Foraging and Reduce Foraging Performance in Honey Bees

There is increasing worldwide concern about the impacts of pesticide residues on honey bees and bee colony survival, but how sublethal effects of pesticides on bees might cause colony failure remains highly controversial, with field data giving very mixed results. To explore how trace levels of the neonicotinoid pesticide imidacloprid impacted colony foraging performance, we equipped bees with RFID tags that allowed us to track their lifetime flight behavior. One group of bees was exposed to a trace concentration (5 μg/kg, ppb) of imidacloprid in sugar syrup while in the larval stage. The imidacloprid residues caused bees to start foraging when younger as adults and perform fewer orientation flights, and reduced their lifetime foraging flights by 28%. The magnitude of the effects of a trace imidacloprid concentration delivered only during larval stage highlights the severity of pesticide residues for bee foraging performance. Our data suggest that neonicotinoids could impact colony function by imbalancing the normal age based division of labor in a colony and reducing foraging efficiency. Understanding this mechanism will help the development of interventions to safeguard bee colony health.

Relationship of Landscape Type on Neonicotinoid Insecticide Exposure Risks to Honey Bee Colonies: A Statewide Survey

Neonicotinoid insecticide use has been suggested as a cause of honey bee colony decline; however, detection rates and concentrations of neonicotinoid insecticide residues in field-collected honey bees have been low. We collected honey bee and beebread samples from apiaries in agricultural, developed, and undeveloped areas during 2 years in Virginia to assess whether landscape type or county pesticide use was predictive of honey bee colony exposure to neonicotinoid insecticides. Trace concentrations of the neonicotinoid imidacloprid were detected in honey bees (3 of 84 samples, 2.02-3.97 ng/g), whereas higher concentrations were detected in beebread (5 of 84 samples, 4.68-11.5 ng/g) and pollen (three of five pollen trap samples, 7.86-12.6 ng/g). Imidacloprid was only detected in samples collected during July and August and was not detected in honey bees from hives where neonicotinoids were detected in pollen or beebread. The number of hives sampled at a site, county pesticide use, and landscape characteristics were not predictive of neonicotinoid detections in honey bees or beebread (all P > 0.05). Field surveys may underestimate honey bee exposure to field-realistic levels of pesticides or the risk of exposure in different landscapes because of low detection rates. Undetectably low levels of exposure or high levels of exposure that go undetected raise questions with regard to potential threats to honey bees and other pollinators.

Toward harmonizing ecotoxicity characterization in life cycle impact assessment

Ecosystem quality is an important area of protection in life cycle impact assessment (LCIA). Chemical pollution has adverse impacts on ecosystems on a global scale. To improve methods for assessing ecosystem impacts, the Life Cycle Initiative hosted by the United Nations Environment Programme established a task force to evaluate the state-of-the-science in modeling chemical exposure of organisms and the resulting ecotoxicological effects for use in LCIA. The outcome of the task force work will be global guidance and harmonization by recommending changes to the existing practice of exposure and effect modeling in ecotoxicity characterization. These changes will reflect the current science and ensure the stability of recommended practice. Recommendations must work within the needs of LCIA in terms of 1) operating on information from any inventory reporting chemical emissions with limited spatiotemporal information, 2) applying best estimates rather than conservative assumptions to ensure unbiased comparison with results for other impact categories, and 3) yielding results that are additive across substances and life cycle stages and that will allow a quantitative expression of damage to the exposed ecosystem. We describe the current framework and discuss research questions identified in a roadmap. Primary research questions relate to the approach toward ecotoxicological effect assessment, the need to clarify the method's scope and interpretation of its results, the need to consider additional environmental compartments and impact pathways, and the relevance of effect metrics other than the currently applied geometric mean of toxicity effect data across species. Because they often dominate ecotoxicity results in LCIA, we give metals a special focus, including consideration of their possible essentiality and changes in environmental bioavailability. We conclude with a summary of key questions along with preliminary recommendations to address them as well as open questions that require additional research efforts. Environ Toxicol Chem 2018;37:2955-2971. © 2018 SETAC.

Climate change-driven range losses among bumblebee species are poised to accelerate

Climate change has shaped bee distributions over the past century. Here, we conducted the first species-specific assessment of future climate change impacts on North American bumblebee distributions, using the most recent global change scenarios developed in the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC). We assessed potential shifts in bumblebee species distributions with models generated using Maxent. We tested different assumptions about bumblebee species’ dispersal capacities, drawing on observed patterns of range shifts to date, dispersal rates observed for bumblebee queens, and, lastly, assuming unlimited dispersal. Models show significant contractions of current ranges even under scenarios in which dispersal rates were high. Results suggest that dispersal rates may not suffice for bumblebees to track climate change as rapidly as required under any IPCC scenario for future climate change. Areas where species losses are projected overlap for many species and climate scenarios, and are concentrated in eastern parts of the continent. Models also show overlap for range expansions across many species, suggesting the presence of “hotspots” where management activities could benefit many species, across all climate scenarios. Broad-scale strategies are likely to be necessary to improve bumblebee conservation prospects under climate change.