Neonicotinoids thiamethoxam and clothianidin adversely affect the colonisation of invertebrate populations in aquatic microcosms

RNA-Seq analysis of Phanerochaete sordida YK-624 degrades neonicotinoid pesticide acetamiprid

Acetamiprid (ACE) belongs to the group of neonicotinoid pesticides, which have become the most widely utilised pesticides around the world in the last two decades. The ability of Phanerochaete sordida YK-624 to degrade ACE under ligninolytic conditions has been demonstrated; however, the functional genes involved in ACE degradation have not been fully elucidated. In the present study, the differentially expressed genes of P. sordida YK-624 under ACE-degrading conditions and in the absence of ACE were elucidated by RNA sequencing (RNA-Seq). Based on the gene ontology enrichment results, the cell wall and cell membrane were significantly affected under ACE-degrading conditions. This result suggested that intracellular degradation of ACE might be mediated by this fungus. In addition, genes in metabolic pathways were the most enriched upregulated differentially expressed genes according to the KEGG pathway analysis. Eleven differentially expressed genes characterised as cytochrome P450s were upregulated, and these genes were determined to be particularly important for ACE degradation by P. sordida YK-624 under ligninolytic conditions.

Dissipation, Bioconcentration and Dietary Risk Assessment of Thiamethoxam and Its Metabolites in Agaricus bisporus and Substrates under Different Application Methods

In order to acquire scientific evidence for the application of thiamethoxam (TMX) in Agaricus bisporus cultivation, residue and dissipation experiments for field trials were performed with the application of TMX in compost and casing soil, respectively. An effective QuEChERS method was established to analyze TMX and its two metabolites, clothianidin (CLO) and thiamethoxam-urea (TMX-urea), in compost, casing soil, and fruiting bodies. The results indicated that the TMX dissipation half-lives (t_1/2) at dosages of 10 and 50 mg kg^-1 were 19.74 d (day) and 28.87 d in compost and 33.54 d and 42.59 d in casing soil, individually. TMX, CLO, and TMX-urea were observed after TMX application in compost and casing soil. For TMX applied to the casing soil, only TMX residues were detected in fruiting bodies with bioconcentration factors (BCFs) of 0.0003~0.0009. In addition, both the chronic risk quotient (RQ) and acute risk quotient (HQ) values of TMX in fruiting bodies were far less than 1, which means the dietary health risks to humans were acceptable. However, in the TMX application to the compost, these analytes were not detected in the fruiting bodies. This suggested that the application of TMX in compost was safer than in casing soil during A. bisporus cultivation.

The multigenerational effects of clothianidin on Chironomus xanthus: Larvae exposed to this acetylcholine super agonist show no clear resistance

Clothianidin (CLO) is an insecticide belonging to the second-generation class of neonicotinoids. In this study, we evaluated how CLO affects the survival and the complete life cycle of the tropical insect Chironomus xanthus, a non-target species, considering the Parental (P) and Filial (F1) generations. We found a 48 h-lethal concentration (LC₅₀) of CLO of 3.78 µg/L. The lowest observed effect concentrations (LOECs) were: i) for body growth and head capsule width in P generation = 47.3 ng/L CLO; ii) for body growth and head capsule width in F1 generation larvae = 80 and 36.4 ng/L CLO, respectively; iii) for cumulative emergence it was 80 ng/L CLO in the P generation, while there was no significant difference in the F1 generation; iv) for total developmental time for males and females = 61.53 ng/L in P generation; v) in the F1 generation, the LOEC was determined to be 36.4 ng/L for males and 80 ng/L for females; vi) The number of total hatched eggs and total hatched eggs/female had LOECs of 36.4 ng/L CLO for both generations. Our study reveals that environmentally relevant concentrations of the CLO-based insecticide are highly toxic to C. xanthus. It also shows that the F1 generation, resulting from parents exposed to CLO was not clearly resistant to the insecticide. This fact might be explained by the different effects observed for males and females of F1 generation. Understanding the sub-types of acetylcholine receptors present on target and non-target insect species and toxicological effects of neonicotinoids seems to be desirable for the insecticide industry to deal with insect pests and the environmental protection of non-target organisms.

Acute toxic effects of thiamethoxam on Chinese mitten crab Eriocheir sinensis

The information about toxic effects of thiamethoxam on non-target aquatic organisms is still incomplete. The semi-static toxicity test method was used to investigate the acute toxic effects of thiamethoxam on Eriocheir sinensis. The results showed that the median lethal concentration (LC50) of thiamethoxam to E. sinensis at 96 h was 510 μg/L, and the safety concentration (SC) was 51 μg/L. After 96 h exposure to thiamethoxam, the survival rates of crabs at concentrations of 0, 151.11, 226.67, 340, and 510 μg/L were 100%, 76.19%, 64.29%, 61.91%, and 46.43%, respectively. A significant (P < 0.05) decrease of the number of hemocytes was observed in thiamethoxam groups. With the increase of thiamethoxam concentration, the phagocytic activity of hemocytes, the activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), total antioxidant capacity (T-AOC), and the activities of protease, amylase, and lipase of crabs increased firstly and then decreased, and the above indexes reached the maximum in 151.11 μg/L thiamethoxam group. Collectively, a high concentration of thiamethoxam (510 μg/L) had a great effect on the gene expression of immune metabolism-related factors in hepatopancreas and gill of crabs. These findings indicated that thiamethoxam exposure had the ability to impair immune and metabolic systems and resulted in the reduction of survival rate of crabs.

Ecotoxicological Studies on the Action of Actara 25 WG Insecticide on Prussian Carp (Carassius gibelio) and Marsh Frog (Pelophylax ridibundus)

The toxic action of the Actara 25 WG insecticide (it contains 25% thiamethoxam as an active substance) in non-lethal doses was studied in two species of aquatic organisms—the Prussian carp (Carassius gibelio) and the marsh frog (Pelophylax ridibundus)—at two thermal levels, 6–8 °C (low temperature) and 18–20 °C (room temperature), respectively. In the Prussian carp, we recorded decreases in oxygen consumption and stimulation of the respiratory rhythm, changes that were more pronounced in the case of intoxicated fish and when the species were kept at room temperature. The histopathology of the lung in the frog illustrated the thickening of the conjunctival septum, an increase in the number of mucous cells, and an increase in the ratio between the diameter of the nucleus and the diameter of the pneumocyte. All of these changes were more pronounced in the animals kept at higher temperature. Our study looks at the extent to which temperature changes can influence the ability of poikilothermic organisms to withstand the presence of toxic substances in the environment as a result of the impact of the use of insecticides in agriculture. The two tested organisms are a common presence for the study area, which was affected in the last decade by climate change.

Juvenile African Clawed Frogs (Xenopus laevis) Express Growth, Metamorphosis, Mortality, Gene Expression, and Metabolic Changes When Exposed to Thiamethoxam and Clothianidin

Neonicotinoids (NEO) represent the main class of insecticides currently in use, with thiamethoxam (THX) and clothianidin (CLO) primarily applied agriculturally. With few comprehensive studies having been performed with non-target amphibians, the aim was to investigate potential biomarker responses along an adverse outcome pathway of NEO exposure, whereby data were collected on multiple biological hierarchies. Juvenile African clawed frogs, Xenopus laevis, were exposed to commercial formulations of THX and CLO at high (100 ppm) and low (20 ppm) concentrations of the active ingredient. Mortality, growth, development, liver metabolic enzyme activity, and gene expression endpoints were quantified. Tadpoles (n > 1000) from NF 47 through tail resorption stage (NF 66) were exposed to NEO or to NEO-free media treatments. Liver cell reductase activity and cytotoxicity were quantified by flow cytometry. Compared to control reference gene expressions, levels of expression for NEO receptor subunits, cell structure, function, and decontamination processes were measured by RT-qPCR by using liver and brain. Mortality in THX high was 21.5% compared to the control (9.1%); the metabolic conversion of THX to CLO may explain these results. The NF 57 control tadpoles were heavier, longer, and more developed than the others. The progression of development from NF 57-66 was reduced by THX low, and weight gain was impaired. Liver reductases were highest in the control (84.1%), with low NEO exhibiting the greatest reductions; the greatest cytotoxicity was seen with THX high. More transcriptional activity was noted in brains than in livers. Results affirm the utility of a study approach that considers multiple complexities in ecotoxicological studies with non-target amphibians, underscoring the need for simultaneously considering NEO concentration-response relationships with both whole-organism and biomarker endpoints.

Physiological Effects of Neonicotinoid Insecticides on Non-Target Aquatic Animals-An Updated Review

In this paper, we review the effects of large-scale neonicotinoid contaminations in the aquatic environment on non-target aquatic invertebrate and vertebrate species. These aquatic species are the fauna widely exposed to environmental changes and chemical accumulation in bodies of water. Neonicotinoids are insecticides that target the nicotinic type acetylcholine receptors (nAChRs) in the central nervous systems (CNS) and are considered selective neurotoxins for insects. However, studies on their physiologic impacts and interactions with non-target species are limited. In researches dedicated to exploring physiologic and toxic outcomes of neonicotinoids, studies relating to the effects on vertebrate species represent a minority case compared to invertebrate species. For aquatic species, the known effects of neonicotinoids are described in the level of organismal, behavioral, genetic and physiologic toxicities. Toxicological studies were reported based on the environment of bodies of water, temperature, salinity and several other factors. There exists a knowledge gap on the relationship between toxicity outcomes to regulatory risk valuation. It has been a general observation among studies that neonicotinoid insecticides demonstrate significant toxicity to an extensive variety of invertebrates. Comprehensive analysis of data points to a generalization that field-realistic and laboratory exposures could result in different or non-comparable results in some cases. Aquatic invertebrates perform important roles in balancing a healthy ecosystem, thus rapid screening strategies are necessary to verify physiologic and toxicological impacts. So far, much of the studies describing field tests on non-target species are inadequate and in many cases, obsolete. Considering the current literature, this review addresses important information gaps relating to the impacts of neonicotinoids on the environment and spring forward policies, avoiding adverse biological and ecological effects on a range of non-target aquatic species which might further impair the whole of the aquatic ecological web.

Commentary: Novel strategies and new tools to curtail the health effects of pesticides

BACKGROUND

Flaws in the science supporting pesticide risk assessment and regulation stand in the way of progress in mitigating the human health impacts of pesticides. Critical problems include the scope of regulatory testing protocols, the near-total focus on pure active ingredients rather than formulated products, lack of publicly accessible information on co-formulants, excessive reliance on industry-supported studies coupled with reticence to incorporate published results in the risk assessment process, and failure to take advantage of new scientific opportunities and advances, e.g. biomonitoring and "omics" technologies.

RECOMMENDED ACTIONS

Problems in pesticide risk assessment are identified and linked to study design, data, and methodological shortcomings. Steps and strategies are presented that have potential to deepen scientific knowledge of pesticide toxicity, exposures, and risks. We propose four solutions: (1) End near-sole reliance in regulatory decision-making on industry-supported studies by supporting and relying more heavily on independent science, especially for core toxicology studies. The cost of conducting core toxicology studies at labs not affiliated with or funded directly by pesticide registrants should be covered via fees paid by manufacturers to public agencies. (2) Regulators should place more weight on mechanistic data and low-dose studies within the range of contemporary exposures. (3) Regulators, public health agencies, and funders should increase the share of exposure-assessment resources that produce direct measures of concentrations in bodily fluids and tissues. Human biomonitoring is vital in order to quickly identify rising exposures among vulnerable populations including applicators, pregnant women, and children. (4) Scientific tools across disciplines can accelerate progress in risk assessments if integrated more effectively. New genetic and metabolomic markers of adverse health impacts and heritable epigenetic impacts are emerging and should be included more routinely in risk assessment to effectively prevent disease.

CONCLUSIONS

Preventing adverse public health outcomes triggered or made worse by exposure to pesticides will require changes in policy and risk assessment procedures, more science free of industry influence, and innovative strategies that blend traditional methods with new tools and mechanistic insights.

Indirect Effect of Pesticides on Insects and Other Arthropods

Pesticides released to the environment can indirectly affect target and non-target species in ways that are often contrary to their intended use. Such indirect effects are mediated through direct impacts on other species or the physical environment and depend on ecological mechanisms and species interactions. Typical mechanisms are the release of herbivores from predation and release from competition among species with similar niches. Application of insecticides to agriculture often results in subsequent pest outbreaks due to the elimination of natural enemies. The loss of floristic diversity and food resources that result from herbicide applications can reduce populations of pollinators and natural enemies of crop pests. In aquatic ecosystems, insecticides and fungicides often induce algae blooms as the chemicals reduce grazing by zooplankton and benthic herbivores. Increases in periphyton biomass typically result in the replacement of arthropods with more tolerant species such as snails, worms and tadpoles. Fungicides and systemic insecticides also reduce nutrient recycling by impairing the ability of detritivorous arthropods. Residues of herbicides can reduce the biomass of macrophytes in ponds and wetlands, indirectly affecting the protection and breeding of predatory insects in that environment. The direct impacts of pesticides in the environment are therefore either amplified or compensated by their indirect effects.

Neonicotinoid residues in honey from urban and rural environments

Pesticide residues in honey can negatively affect bee health. Although recent studies have detected neonicotinoid residues in honeys from around the world, little is known about how residues relate to land use and vegetation composition. To investigate potential relationships, we sampled multi-floral honey from 30 Apis mellifera hives from urban, agricultural and semi-natural habitats (SNH), identified and quantified three neonicotinoids present (clothianidin, imidacloprid and thiacloprid) using UHPLC-MS, and classified surrounding land use up to 5 km around hive sites. Neonicotinoids were most frequently detected in honeys from hives in agricultural habitats, and 70% of all samples contained at least one of the three neonicotinoid compounds. Imidacloprid was the most frequently detected neonicotinoid (found in 43% of honey samples) followed by clothianidin (40%) and thiacloprid (37%). Almost half (48%) of samples contained at least two neonicotinoids, and two of the 30 samples contained all three. Clothianidin and thiacloprid were more frequently detected in honeys from urban habitats, highlighting that exposure to pesticides does not just occur in agricultural settings. This suggests that pesticide use in urban domestic, sport and amenity contexts, given potential exposure of bees and other pollinators, needs urgent consideration.

Prioritization of Pesticides for Assessment of Risk to Aquatic Ecosystems in Canada and Identification of Knowledge Gaps

Pesticides can enter aquatic environments via direct application, via overspray or drift during application, or by runoff or leaching from fields during rain events, where they can have unintended effects on non-target aquatic biota. As such, Fisheries and Oceans Canada identified a need to prioritize current-use pesticides based on potential risks towards fish, their prey species, and habitats in Canada. A literature review was conducted to: (1) Identify current-use pesticides of concern for Canadian marine and freshwater environments based on use and environmental presence in Canada, (2) Outline current knowledge on the biological effects of the pesticides of concern, and (3) Identify general data gaps specific to biological effects of pesticides on aquatic species. Prioritization was based upon recent sales data, measured concentrations in Canadian aquatic environments between 2000 and 2020, and inherent toxicity as represented by aquatic guideline values. Prioritization identified 55 pesticides for further research nationally. Based on rank, a sub-group of seven were chosen as the top-priority pesticides, including three herbicides (atrazine, diquat, and S-metolachlor), three insecticides (chlorpyrifos, clothianidin, and permethrin), and one fungicide (chlorothalonil). A number of knowledge gaps became apparent through this process, including gaps in our understanding of sub-lethal toxicity, environmental fate, species sensitivity distributions, and/or surface water concentrations for each of the active ingredients reviewed. More generally, we identified a need for more baseline fish and fish habitat data, ongoing environmental monitoring, development of marine and sediment-toxicity benchmarks, improved study design including sufficiently low method detection limits, and collaboration around accessible data reporting and management.

Neonicotinoid Insecticides: Molecular Targets, Resistance, and Toxicity

Neonicotinoids have been used to protect crops and animals from insect pests since the 1990s, but there are concerns regarding their adverse effects on nontarget organisms, notably on bees. Enhanced resistance to neonicotinoids in pests is becoming well documented. We address the current understanding of neonicotinoid target site interactions, selectivity, and metabolism not only in pests but also in beneficial insects such as bees. The findings are relevant to the management of both neonicotinoids and the new generation of pesticides targeting insect nicotinic acetylcholine receptors.

Movement of the Neonicotinoid Seed Treatment Clothianidin into Groundwater, Aquatic Plants, and Insect Herbivores

Agricultural use of the neonicotinoid clothianidin (CLO) as a seed treatment of corn and soybeans has been linked to contamination of waterways and irrigation water. By analyzing samples collected from field lysimeters with liquid chromatography tandem mass spectrometry (LC-MS), this study reports the highest CLO concentrations within leachate following planting, with maximum concentrations occurring 4 weeks post-planting (3370 ng L^-1). This concentration is approximately 10× greater than previously reported CLO concentrations in streams/rivers and prairie wetlands, likely the result of reduced dilution and photolysis impacts. To document nontarget vegetation translocation dynamics, the macrophyte Lemna gibba was exposed to varying CLO concentrations for 12 h within a laboratory setting. Quantification of CLO uptake occurred every 4 h. Finally, trophic level impacts were investigated by exposing the water lily aphid Rhopalosiphum nymphaeae to L. gibba grown in CLO-contaminated water. Aphids lived and fed on contaminated duckweed for 48 h, after which an LC₅₀ of 8.71 ng g of the plant tissue^-1 was calculated. While uptake of CLO by duckweed was rapid, aphids are unlikely to suffer acute mortality at previously reported environmental CLO concentrations. Future research should expand on this work with other macrophytes/herbivores and longer-term experiments to more realistically mimic chronic field exposures.

A holistic study of neonicotinoids neuroactive insecticides-properties, applications, occurrence, and analysis

Among pesticides and foliar sprays involved in the treatment of seed, soil, and grass, also to crops, an important group is neonicotinoids. Neonicotinoid pesticides present similar properties with nicotine, but the mentioned compounds are less harmful for humans. Nevertheless, neonicotinoids are poisonous to insects and some invertebrates, which can act against insects' central nervous system, leading to their death. Moreover, neonicotinoids can affect the reproduction, foraging, and flying ability of honeybee and other insects including pollinators. In the present study, some neonicotinoids, such as imidacloprid, acetamiprid, clothianidin, thiacloprid, and thiamethoxam together with their toxic effects, have been presented. The Environmental Protection Agency (EPA) classifies these neonicotinoids as II and III class toxicity agents. Due to accumulation of these pesticides into the pollen of treated plants, especially due to their toxic effects against pollinators, the consequences of the occurrence of these insecticides have been discussed. Analytical aspects and methods involved in the isolation and determination of this class of pesticides have been presented in this contribution.

Photo-degradation dynamics of five neonicotinoids: Bamboo vinegar as a synergistic agent for improved functional duration

The effects of photo-degradation on the utilization of pesticides in agricultural production has been investigated. Various influencing factors were compared, with results showing that the initial pesticide concentration, light source, water quality and pH possessed different effects on neonicotinoids photo-degradation. The initial concentration and pH were found to be most critical effects. The photo-degradation rate decreased by a factor of 2-4 when the initial concentration increased from 5 mg L-1 to 20 mg L-1, particularly for acetamiprid and imidacloprid. The photo-degradation pathways and products of the five neonicotinoids were also investigated, with similar pathways found for each pesticide, except for acetamiprid. Degradation pathways mainly involved photo-oxidation processes, with products identified using liquid chromatography-quadrupole time-of-flight mass spectrometry (LC-Q-TOF-MS) found to be consistent with literature reported results. Bamboo vinegar exerted a photo-quenching effect on the neonicotinoids, with an improved efficiency at higher vinegar concentrations. The photo-quenching rates of thiamethoxam and dinotefuran were 381.58% and 310.62%, respectively, when a 30-fold dilution of vinegar was employed. The photo-degradation products in bamboo vinegar were identical to those observed in methanol, with acetic acid being the main factor influencing the observed quenching effects.

A survey and risk assessment of neonicotinoids in water, soil and sediments of Belize

Usage of neonicotinoids is common in all agricultural regions of the world but data on environmental contamination in tropical regions is scarce. We conducted a survey of five neonicotinoids in soil, water and sediment samples along gradients from crops fields to protected lowland tropical forest, mangroves and wetlands in northern Belize, a region of high biodiversity value. Neonicotinoid frequency of detection and concentrations were highest in soil (68%) and lowest in water (12%). Imidacloprid was the most common residue reaching a maximum of 17.1 ng/g in soil samples. Concentrations in soils differed among crop types, being highest in melon fields and lowest in banana and sugarcane fields. Residues in soil declined with distance to the planted fields, with clothianidin being detected at 100 m and imidacloprid at more than 10 km from the nearest applied field. About half (47%) of the sediments collected contained residues of at least one compound up to 10 km from the source. Total neonicotinoid concentrations in sediments (range 0.014-0.348 ng/g d. w.) were about 10 times lower than in soils from the fields, with imidacloprid being the highest (0.175 ng/g). A probabilistic risk assessment of the residues in the aquatic environment indicates that 31% of sediment samples pose a risk to invertebrate aquatic and benthic organisms by chronic exposure, whereas less than 5% of sediment samples may incur a risk by acute exposure. Current residue levels in water samples do not appear to pose risks to the aquatic fauna. Fugacity modeling of the four main compounds detected suggest that most of the dissipation from the agricultural fields occurs via runoff and leaching through the porous soils of this region. We call for better monitoring of pesticide contamination and invertebrate inventories and finding alternatives to the use of neonicotinoids in agriculture.