Time-Cumulative Toxicity of Neonicotinoids: Experimental Evidence and Implications for Environmental Risk Assessments

The characterization of developmental toxicity in fetal offspring induced by acetaminophen exposure during pregnancy

OBJECTIVE

Acetaminophen (APAP), an antipyretic and analgesic commonly used during pregnancy, has been recognized as a novel environmental contaminant. Preliminary evidence suggests that prenatal acetaminophen exposure (PAcE) could adversely affect offspring's gonadal and neurologic development, but there is no systematic investigation on the characteristics of APAP's fetal developmental toxicity.

METHODS

Pregnant mice were treated with 100 or 400 mg/kg∙d APAP in the second-trimester, or 400 mg/kg∙d APAP in the second- or third-trimester, or different courses (single or multiple) of APAP, based on clinical regimen. The effects of PAcE on pregnancy outcomes, maternal/fetal blood phenotypes, and multi-organ morphological and functional development of fetal mice were analyzed.

RESULTS

PAcE increased the incidence of adverse pregnancy outcomes and altered blood phenotypes including aminotransferases, lipids, and sex hormones in dams and fetuses. The expression of key functional genes in fetal organs indicated that PAcE inhibited hippocampal synaptic development, sex hormone synthesis, and osteogenic and chondrogenic development, but enhanced hepatic lipid synthesis and uptake, renal inflammatory hyperplasia, and adrenal steroid hormone synthesis. PAcE also induced marked pathological alterations in the fetal hippocampus, bone, kidney, and cartilage. The sensitivity rankings of fetal organs to PAcE might be hippocampus/bone > kidney > cartilage > liver > gonad > adrenal gland. Notably, PAcE-induced multi-organ developmental toxicity was more considerable under high-dose, second-trimester, and multi-course exposure and in male fetuses.

CONCLUSION

This study confirmed PAcE-induced alterations in multi-organ development and function in fetal mice and elucidated its characteristics, which deepens the comprehensive understanding of APAP's developmental toxicity.

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;43:2058-2070. © 2024 The Author(s). Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Environmental ameliorations and politics in support of pollinators. Experiences from Europe: A review

At least 87% of angiosperm species require animal vectors for their reproduction, while more than two-thirds of major global food crops depend on zoogamous pollination. Pollinator insects are a wide variety of organisms that require diverse biotic and abiotic resources. Many factors have contributed to a serious decrease in the abundance of populations and diversity of pollinator species over the years. This decline is alarming, and the European Union has taken several actions aimed at counteracting it by issuing new conservation policies and standardizing the actions of member countries. In 2019, the European Green Deal was presented, aiming to restore 100% of Europe's degraded land by 2050 through financial and legislative instruments. Moreover, the Common Agricultural Policies have entailed greening measures for the conservation of habitats and beneficial species for more than 10 years. The new CAP (CAP 23-27) reinforces conservation objectives through strategic plans based on eco-schemes defined at the national level by the member countries, and some states have specifically defined eco-schemes for pollinator conservation. Here, we review the framework of EU policies, directives, and regulations, which include measures aimed at protecting pollinators in agricultural, urban, and peri-urban environments. Moreover, we reviewed the literature reporting experimental works on the environmental amelioration for pollinators, particularly those where CAP measures were implemented and evaluated, as well as studies conducted in urban areas. Among CAP measures, several experimental works have considered the sowing and management of entomophilous plants and reported results important for environmental ameliorations. Some urban, peri-urban and wasteland areas have been reported to host a considerable number of pollinators, especially wild bees, and despite the lack of specific directives, their potential to contribute to pollinator conservation could be enhanced through targeted actions, as highlighted by some studies.

Transfer and bioaccumulation of pesticides in terrestrial arthropods and food webs: State of knowledge and perspectives for research

Arthropods represent an entry point for pesticide transfers in terrestrial food webs, and pesticide accumulation in upper chain organisms, such as predators can have cascading consequences on ecosystems. However, the mechanisms driving pesticide transfer and bioaccumulation in food webs remain poorly understood. Here we review the literature on pesticide transfers mediated by terrestrial arthropods in food webs. The transfer of pesticides and their potential for bioaccumulation and biomagnification are related to the chemical properties and toxicokinetic of the substances, the resistance and detoxification abilities of the contaminated organisms, as well as by their effects on organisms' life history traits. We further identify four critical areas in which knowledge gain would improve future predictions of pesticides impacts on terrestrial food webs. First, efforts should be made regarding the effects of co-formulants and pesticides mixtures that are currently understudied. Second, progress in the sensitivity of analytical methods would allow the detection of low concentrations of pesticides in small individual arthropods. Quantifying pesticides in arthropods preys, their predators, and arthropods or vertebrates at higher trophic level would bring crucial insights into the bioaccumulation and biomagnification potential of pesticides in real-world terrestrial food webs. Finally, quantifying the influence of the trophic structure and complexity of communities on the transfer of pesticides could address several important sources of variability in bioaccumulation and biomagnification across species and food webs. This narrative review will inspire future studies aiming to quantify pesticide transfers in terrestrial food webs to better capture their ecological consequences in natural and cultivated landscapes.

Neonicotinoid insecticides in waters of the northern Jiangsu segment of the Beijing-Hangzhou Grand Canal: Environmental and health implications

Neonicotinoid (NEO) insecticides have been frequently detected in natural aquatic environments. Nevertheless, the distribution of NEOs in artificial environments is not clear. The Beijing-Hangzhou Grand Canal is the longest canal in the world. The northern Jiangsu segment of the Grand Canal was selected to study the spatiotemporal variation and source of eight NEOs in the canal water and assess their ecological and health risks. The total NEO concentration in the canal water was 12-289 ng L-1 in the dry season and 18-373 ng L-1 in the wet season, which were within the concentration range in other 11 natural rivers worldwide. The average total NEO concentrations were not statistically different between the seasons; only the concentrations of imidaclothiz, thiacloprid (THI), acetamiprid, and dinotefuran were different. At city scale, the total NEO concentration in the dry season showed a decreasing trend along the water flow from Xuzhou City to Yangzhou City. The total NEO concentrations were found to be positively correlated with the sown area of farm crops and the rural labour force, indicating the agricultural influence on the spatial distribution of NEO concentrations. In the wet season, relatively high NEO concentrations were distributed in downstream sites under the influence of artificial regulation. The primary contributor to the NEO inputs into the canal was the nonpoint source in the dry and wet seasons, with a relative contribution of 68 %. THI, imidacloprid, clothianidin and thiamethoxan would produce chronic ecological risks in both seasons. Further consideration needs to be given to the above four NEOs and NEO mixtures. The human health risks that NEOs posed by drinking water were assessed based on the chronic daily intake (CDI). The maximum CDI for adults and children was lower than the reference doses. This suggested public health would not be at risk from canal water consumption.

Prenatal amoxicillin exposure induces developmental toxicity in fetal mice and its characteristics

Amoxicillin, a widely used antibiotic in human and veterinary pharmaceuticals, is now considered as an "emerging contaminant" because it exists widespreadly in the environment and brings a series of adverse outcomes. Currently, systematic studies about the developmental toxicity of amoxicillin are still lacking. We explored the potential effects of amoxicillin exposure on pregnancy outcomes, maternal/fetal serum phenotypes, and fetal multiple organ development in mice, at different doses (75, 150, 300 mg/(kg·day)) during late-pregnancy, or at a dose of 300 mg/(kg·day) during different stages (mid-/late-pregnancy) and courses (single-/multi-course). Results showed that prenatal amoxicillin exposure (PAmE) had no significant influence on the body weights of dams, but it could inhibit the physical development and reduce the survival rate of fetuses, especially during the mid-pregnancy. Meanwhile, PAmE altered multiple maternal/fetal serum phenotypes, especially in fetuses. Fetal multi-organ function results showed that PAmE inhibited testicular/adrenal steroid synthesis, long bone/cartilage and hippocampal development, and enhanced ovarian steroid synthesis and hepatic glycogenesis/lipogenesis, and the order of severity might be gonad (testis, ovary) > liver > others. Further analysis found that PAmE-induced multi-organ developmental and functional alterations had differences in stages, courses and fetal gender, and the most obvious changes might be in high-dose, late-pregnancy and multi-course, but there was no typical rule of a dose-response relationship. In conclusion, this study confirmed that PAmE could cause abnormal development and multi-organ function alterations, which deepens our understanding of the risk of PAmE and provides an experimental basis for further exploration of the long-term harm.

Passive sampling of herbicides above sediments at sites with losses of submerged macrophytes in a mesotrophic lake

Declines of submerged macrophytes (SUM) were monitored in littoral zones of the deep, mesotrophic lake Suhrer See (Northern Germany) since 2017. Drastic losses coincided with intense agriculture in sandy sub-catchments and precipitation. All lines of evidence pointed to a causal connection with subsurface discharge indicating that herbicide application might have caused the effects. Passive sampling was applied in 2022 to elucidate, whether herbicides were really present at sites of losses and if so, in ecotoxicological relevant concentrations. Samplers were exposed on top of lake sediments in 2 m depth and under worst case conditions, i.e., at sites, known for losses of the whole functional group of SUM and at the beginning of the vegetation period. At this time, SUM diaspores were most vulnerable to repression of development and the subsurface discharge was high in the same instance. The potential ecotoxicological relevance of detected herbicide concentrations was assessed with a toxic units (TU) approach, with reference to acute effect concentrations (EC50 of green algae, 72 h, growth). The TU ranged from 0.001 to 0.03. Most concentrations exceeded the threshold of relevance set by an assessment factor of 1000, i.e., TU > 0.001. Locally applied herbicides acted by suppressing developmental stages, and the sum of TU exceeded 0.02 at all sites, mainly due to diflufenican. Not applied locally, terbuthylazine and its relevant metabolites, including terbutryn, acted by inhibiting photosynthesis, and the sum of TU reached 0.005. On this base, diflufenican was assessed to be likely a main stressor, all other detected herbicides to be potentially relevant. Uncertainties and knowledge gaps were specified. The result of the chemical risk assessment was counterchecked for consistence with biological monitoring data within a whole lake perspective. Concepts of empirical and advanced causal attribution methodology were applied to get a grip to the ecological causal field and to protection.

Imidacloprid increases the prevalence of the intestinal parasite Lotmaria passim in honey bee workers

A challenge in bee protection is to assess the risks of pesticide-pathogen interactions. Lotmaria passim, a ubiquitous unicellular parasite in honey bees, is considered harmful under specific conditions. Imidacloprid causes unpredictable side effects. Research indicates that both L. passim and imidacloprid may affect the physiology, behavior, immunity, microbiome and lifespan of honey bees. We designed cage experiments to test whether the infection of L. passim is affected by a sublethal dose of imidacloprid. Workers collected at the time of emergence were exposed to L. passim and 2.5 μg/L imidacloprid in the coexposure treatment group. First, samples of bees were taken from cages since they were 5 days old and 3 days postinfection, i.e., after finishing an artificial 24 h L. passim infection. Additional bees were collected every two additional days. In addition, bees frozen at the time of emergence and collected from the unexposed group were analyzed. Abdomens were analyzed using qPCR to determine parasite load, while corresponding selected heads were subjected to a label-free proteomic analysis. Our results show that bees are free of L. passim at the time of emergence. Furthermore, imidacloprid considerably increased the prevalence as well as parasite loads in individual bees. This means that imidacloprid facilitates infection, enabling faster parasite spread in a colony and potentially to surrounding colonies. The proteomic analysis of bee heads showed that imidacloprid neutralized the increased transferrin 1 expression by L. passim. Importantly, this promising marker has been previously observed to be upregulated by infections, including gut parasites. This study contributes to understanding the side effects of imidacloprid and demonstrates that a single xenobiotic/pesticide compound can interact with the gut parasite. Our methodology can be used to assess the effects of different compounds on L. passim.

Breaking the cycle: Reforming pesticide regulation to protect pollinators

Over decades, pesticide regulations have cycled between approval and implementation, followed by the discovery of negative effects on nontarget organisms that result in new regulations, pesticides, and harmful effects. This relentless pattern undermines the capacity to protect the environment from pesticide hazards and frustrates end users that need pest management tools. Wild pollinating insects are in decline, and managed pollinators such as honey bees are experiencing excessive losses, which threatens sustainable food security and ecosystem function. An increasing number of studies demonstrate the negative effects of field-realistic exposure to pesticides on pollinator health and fitness, which contribute to pollinator declines. Current pesticide approval processes, although they are superior to past practices, clearly continue to fail to protect pollinator health. In the present article, we provide a conceptual framework to reform cyclical pesticide approval processes and better protect pollinators.

Sublethal Effects of Four Insecticides Targeting Cholinergic Neurons on Partner and Host Finding in the Parasitic Wasp Nasonia vitripennis

Lethal and sublethal effects of pesticides on nontarget organisms are one of the causes of the current decline of many insect species. However, research in the past decades has focused primarily on pollinators, although other beneficial nontarget organisms such as parasitic wasps may also be affected. We studied the sublethal effects of the four insecticides acetamiprid, dimethoate, flupyradifurone, and sulfoxaflor on pheromone-mediated sexual communication and olfactory host finding of the parasitic wasp Nasonia vitripennis. All agents target cholinergic neurons, which are involved in the processing of chemical information by insects. We applied insecticide doses topically and tested the response of treated wasps to sex pheromones and host-associated chemical cues. In addition, we investigated the mating rate of insecticide-treated wasps. The pheromone response of females surviving insecticide treatment was disrupted by acetamiprid (≥0.63 ng), dimethoate (≥0.105 ng), and flupyradifurone (≥21 ng), whereas sulfoxaflor had no significant effects at the tested doses. Olfactory host finding was affected by all insecticides (acetamiprid ≥1.05 ng, dimethoate ≥0.105 ng, flupyradifurone ≥5.25 ng, sulfoxaflor ≥0.52 ng). Remarkably, females treated with ≥0.21 ng dimethoate even avoided host odor. The mating rate of treated N. vitripennis couples was decreased by acetamiprid (6.3 ng), flupyradifurone (≥2.63 ng), and sulfoxaflor (2.63 ng), whereas dimethoate showed only minor effects. Finally, we determined the amount of artificial nectar consumed by N. vitripennis females within 48 h. Considering this amount (∼2 µL) and the maximum concentrations of the insecticides reported in nectar, tested doses can be considered field-realistic. Our results suggest that exposure of parasitic wasps to field-realistic doses of insecticides targeting the cholinergic system reduces their effectiveness as natural enemies by impairing the olfactory sense. Environ Toxicol Chem 2023;42:2400-2411. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Residues of sulfoxaflor and its metabolites in floral and extrafloral nectar from Hibiscus rosa-sinensis L. (Malvaceae) with or without co-application of tebuconazole

Systemic pesticide exposure through nectar is a growing global concern linked to loss of insect diversity, especially pollinators. The insecticide sulfoxaflor and the fungicide tebuconazole are currently widely used systemic pesticides which are toxic to certain pollinators. However, their metabolisms in floral or extrafloral nectar under different application methods have not yet been well studied. Hibiscus rosa-sinensis was exposed to sulfoxaflor and tebuconazole via soil drenching and foliar spraying. Sulfoxaflor, tebuconazole, and their main metabolites in floral and extrafloral nectar, soil, and leaves were identified and quantified using liquid chromatography coupled with triple quadrupole mass spectrometry (LC-QqQ MS). The chemical compositions of unexposed and contaminated H. rosa-sinensis floral nectar or extrafloral nectar were compared using regular biochemical methods. The activities of two pesticide detoxifying enzymes, glutathione-s-transferase and nitrile hydratase, in H. rosa-sinensis nectar were examined using LC-MS and spectrophotometry. The floral nectar proteome of H. rosa-sinensis was analysed using high-resolution orbitrap-based MS/MS analysis to screen for sulfoxaflor and tebuconazole detoxifying enzymes. H. rosa-sinensis can absorb sulfoxaflor and tebuconazole through its roots or leaf surfaces and secrete them into floral nectar and extrafloral nectar. Both sulfoxaflor and tebuconazole and their major metabolites were present at higher concentrations in extrafloral nectar than in floral nectar. X11719474 was the dominant metabolite of sulfoxaflor in the nectars we studied. Compared with soil application, more sulfoxaflor and tebuconazole remained in their original forms in floral nectar and extrafloral nectar after foliar application. Sulfoxaflor and tebuconazole exposure did not modify the chemical composition of floral or extrafloral nectar. No active components, including proteins in the nectar, were detected to be able to detoxify sulfoxaflor.

Selected neonicotinoids and associated risk for aquatic organisms

Neonicotinoids are one of the newest groups of systemic pesticides, effective on a wide range of invertebrate pests. The success of neonicotinoids can be assessed according to the amount used, for example, in the Czech Republic, which now accounts for 1/3 of the insecticide market. The European Union (EU) has a relatively interesting attitude towards neonicotinoids. Three neonicotinoid substances (imidacloprid, clothianidin and thiamethoxam) were severely restricted in 2013. In 2019, imidacloprid and clothianidin were banned, while thiamethoxam and thiacloprid were banned in 2020. In 2022, another substance, sulfoxaflor, was banned. Therefore, only two neonicotinoid substances (acetamiprid and flupyradifurone) are approved for outdoor use in the EU. Neonicotinoids enter aquatic ecosystems in many ways. In European rivers, neonicotinoids usually occur in nanograms per litre. Due to the low toxicity of neonicotinoids to standard test species, they were not expected to significantly impact the aquatic ecosystem until later studies showed that aquatic invertebrates, especially insects, are much more sensitive to neonicotinoids. In addition to the lethal effects, many studies point to sublethal impacts - reduced reproductive capacity, initiation of downstream drift of organisms, reduced ability to eat, or a change in feeding strategies. Neonicotinoids can affect individuals, populations, and entire ecosystems.

Sex-specific alterations in adaptive responses of Chironomus columbiensis triggered by imidacloprid chronic and acute sublethal exposures

The use of imidacloprid is a common pest control practice in the Neotropical region. However, the imidacloprid unintended sublethal effects on Neotropical aquatic non-target arthropods and undesirable consequences for aquatic environments remain unclear. Here, we assessed the susceptibility of Chironomus columbiensis (Diptera: Chironomidae) larvae to the neonicotinoid imidacloprid and evaluated whether sublethal exposure types would trigger sex-dependent adaptive responses (e.g., emergence, body mass, reproduction, wing morphology). We conducted a concentration-mortality curve (96 h of exposure) and established chronic and acute sublethal exposure bioassays. While chronic sublethal exposures consisted of exposing individuals during their entire larval and pupal stages, the acute sublethal exposures represented a single short duration (24 h) exposure episode during either the first or fourth larval instar. Our results revealed that chronic sublethal exposure reduced the body mass of males, while acute sublethal exposures during the first instar resulted in heavier males than those that were not exposed to imidacloprid. Chronic exposure also reduced the reproduction of males and females, while the acute sublethal exposure only affected the reproduction of individuals that were imidacloprid-exposed on their later larval instar. Chronic and acute sublethal exposures did differentially affect the wing properties of C. columbiensis males (e.g., increased size when chronically exposed and highly asymmetric wings when acutely exposed in early larval phase) and females (e.g., highly asymmetric wings when chronically and acutely exposed). Collectively, our findings demonstrated that imidacloprid can cause unintended sublethal effects on C. columbiensis, and those effects are dependent on sex, exposure type, and developmental stage.

Monitoring resistance to methomyl and synergism in the non-target Musca domestica from cotton fields of Punjab and Sindh provinces, Pakistan

Insecticides are an integral part of most of the cropping systems worldwide; however, these usually exert negative impact on the environment and non-target insects as well. Non-target insects are prone to develop resistance to insecticides due to prolonged and repeated lethal and sublethal exposures. Musca domestica is a common non-target, pollinator and nectar feeder species in cotton ecosystem, besides its status as a public health pest in human habitations. In the present work, resistance to methomyl, one of the major insecticides used for cotton pest management, was assessed in 20 M. domestica strains from the major cotton producing areas of the Punjab and Sindh provinces of Pakistan. The results revealed that toxicity values of methomyl for Punjabi and Sindhi strains ranged from 28.07 to 136.16 µg fly^-1 and 29.32 to 136.87 µg fly^-1, respectively. Among Punjabi strains, D.G. Khan, Lodhran, Bahawalpur, Toba Tek Singh, Bahawalnagar, Rajanpur and Jhang strains exhibited very high levels of resistance (RR > 100) to methomyl; Bhakkar, Kasur, Vehari, Layyah, Muzaffargarh and R.Y. Khan showed high resistance (RR = 51-100 fold), while the Mianwali strain showed a moderate level of resistance to methomyl (RR = 36.45 fold). In case of Sindhi strains, very high levels of resistance (> 100 fold) were reported for Sukkar and Sanghar strains, high levels of resistance (RR 51-100 fold) for Khairpur, Jamshoro and Ghotki, and moderate resistance to methomyl (38.08 fold) in the Dadu strain. There was a significant synergism of methomyl toxicity in all field strains when methomyl bioassayed along with piperonyl butoxide (PBO) and S,S,S-tributylphosphorotrithioate (DEF) providing clues of metabolic-based mechanisms of resistance to methomyl. In conclusion, insecticides used in crop farming can cause resistance development in non-target M. domestica. It is necessary to adopt the pest management activities that are safe for the environment and non-target insect species.

Neonicotinoid insecticides in global agricultural surface waters - Exposure, risks and regulatory challenges

Neonicotinoids are the most widely used insecticides worldwide. However, the widespread usage of neonicotinoids has sparked concerns over their effects on non-target ecosystems including surface waters. We present here a comprehensive meta-analysis of 173 peer-reviewed studies (1998-2022) reporting measured insecticide concentrations (MICs; n = 3983) for neonicotinoids in global surface waters resulting from agricultural nonpoint source pollution. We used compound-specific regulatory threshold levels for water (RTL_SW) and sediment (RTL_SED) defined for pesticide authorization in Canada, the EU and the US, and multispecies endpoints (MSE_SW) to assess acute and chronic risks of global neonicotinoid water-phase (MIC_SW; n = 3790) and sediment (MIC_SED; n = 193) concentrations. Results show a complete lack of exposure information for surface waters in >90 % of agricultural areas globally. However, available data indicates for MIC_SW overall acute risks to be low (6.7 % RTL_{SW_acute} exceedances), but chronic risks to be of concern (20.7 % RTL_{SW_chronic} exceedances); exceedance frequencies were particularly high for chronic MSE_SW (63.3 %). We found RTL_SW exceedances to be highest for imidacloprid and in less regulated countries. Linear model analysis revealed risks for global agricultural surface waters to decrease significantly over time, potentially biased by the lack of sensitive analytical methods in early years of neonicotinoid monitoring. The Canadian, EU and US RTL_SW differ considerably (up to factors of 223 for RTL_{SW_acute} and 13,889 for RTL_{SW_chronic}) for individual neonicotinoids, indicating large uncertainties and regulatory challenges in defining robust and protective RTLs. We conclude that protective threshold levels, in concert with increasing monitoring efforts targeting agricultural surface waters worldwide, are essential to further assess the ecological consequences from anticipated increases of agricultural neonicotinoid uses.

Thiamethoxam in soybean seed treatment: Plant bioactivation and hormesis, besides whitefly control?

Amid concerns on the myriad of existing chemical stressors in agroecosystems, pesticides and particularly neonicotinoid insecticides are in the forefront. Despite that, these neurotoxic compounds remain the dominant group of insecticides in worldwide use with the added versatility of use in seed coatings. Such use sparks environmental concerns counterbalanced by their reported insecticidal efficacy and potential plant bioactivation. Nonetheless, this alleged double benefit and interconnection expected with neonicotinoids has been little explored particularly when the whole plant phenology is considered. Regardless of the expected efficacy against targeted insect pest species, like whiteflies, neonicotinoids may spark dual effect on plants - negative at higher concentrations, positive at low concentrations, which is consistent with the hormesis phenomenon that may be expressed as a plant bioactivation. This effect may also cascade to the targeted insect species, what deserves attention. Therefore, soybean seeds treated with increasing concentrations of the neonicotinoid thiamethoxam were followed throughout their development in greenhouse, recording the plant response and yield, besides their effect in whiteflies (Bemisia tabaci MEAM1). Thiamethoxam application was correlated to leaf contents of thiamethoxam and its metabolite clothianidin. Plant hormesis was found for leaf area and root growth, but not for other plant morphological or physiological parameters, nor plant yield. The insecticide concentration-dependency compromised whitefly population growth without evidence of cascading any plant-mediated hormesis to the insects. Thus, although plant hormesis was recognized with thiamethoxam in treated soybean seeds in relevant parameters, no evidence of plant bioactivation was observed to justify its use with such a secondary objective, nor did this hormesis impair whitefly control.

Identification and quantitation of the novel insecticide sulfoxaflor and its metabolites in floral nectar from Salvia splendens Ker Gawl. (Lamiaceae)

Sulfoxaflor is a new systemic insecticide developed as a replacement for older neonicotinoids which are known to be toxic to pollinators. However, its metabolism in nectar and effect on nectar biosynthesis have not been investigated. After soil and foliar application, sulfoxaflor and its main metabolites in soil, leaf and Salvia splendens nectar, were measured by liquid chromatography coupled with triple quadrupole mass spectrometer (LC-MS/MS). The chemical composition between the clean and sulfoxaflor spiked nectar were also compared. The activities of two possible sulfoxaflor detoxifying enzymes in S. splendens nectar, nitrile hydratase and glutathione-s-transferase, were measured by LC-MS and spectrophotometry. S. splendens nectar proteome was investigated by high-resolution orbitrap-based MS/MS to screen for sulfoxaflor detoxifying relevant proteins. S. splendens could absorb sulfoxaflor through root or leaf surface and secrete a proportion of sulfoxaflor along with its metabolites into the nectar. After soil application, sulfoxaflor's low toxic metabolite X11719474 was dominant in the nectar and reached an average concentration of 8905 ppb. However, after foliar application, sulfoxaflor was dominant over its metabolites in the nectar. S. splendens nectar has no nitrile hydratase and glutathione-s-transferase activity and none of the 106 proteins identified in the nectar were predicted to function in detoxifying sulfoxaflor. Soil and foliar sulfoxaflor application can result in different profiles of sulfoxaflor and its metabolites presented in the nectar. However, sulfoxaflor had no effects on S. splendens nectar secretion and chemical composition and cannot be directly detoxified by components in the nectar.

Pesticides in ambient air, influenced by surrounding land use and weather, pose a potential threat to biodiversity and humans

Little is known about (i) how numbers and concentrations of airborne pesticide residues are influenced by land use, interactions with meteorological parameters, or by substance-specific chemo-physical properties, and (ii) what potential toxicological hazards this could pose to non-target organisms including humans. We installed passive air samplers (polyurethane PUF and polyester PEF filter matrices) in 15 regions with different land uses in eastern Austria for up to 8 months. Samples were analyzed for 566 substances by gas-chromatography/mass-spectrometry. We analyzed relationships between frequency and concentrations of pesticides, land use, meteorological parameters, substance properties, and season. We found totally 67 pesticide active ingredients (24 herbicides, 30 fungicides, 13 insecticides) with 10-53 pesticides per site. Herbicides metolachlor, pendimethalin, prosulfocarb, terbuthylazine, and the fungicide HCB were found in all PUF samplers, and glyphosate in all PEF samplers; chlorpyrifos-ethyl was the most abundant insecticide found in 93% of the samplers. Highest concentrations showed the herbicide prosulfocarb (725 ± 1218 ng sample^-1), the fungicide folpet (412 ± 465 ng sample^-1), and the insecticide chlorpyrifos-ethyl (110 ± 98 ng sample^-1). Pesticide numbers and concentrations increased with increasing proportions of arable land in the surroundings. However, pesticides were also found in two National Parks (10 and 33 pesticides) or a city center (17 pesticides). Pesticide numbers and concentrations changed between seasons and correlated with land use, temperature, radiation, and wind, but were unaffected by substance volatility. Potential ecotoxicological exposure of mammals, birds, earthworms, fish, and honeybees increased with increasing pesticide numbers and concentrations. Human toxicity potential of detected pesticides was high, with averaged 54% being acutely toxic, 39% reproduction toxic, 24% cancerogenic, and 10% endocrine disrupting. This widespread pesticide air pollution indicates that current environmental risk assessments, field application techniques, protective measures, and regulations are inadequate to protect the environment and humans from potentially harmful exposure.

Long-Term Effects of Imidacloprid, Thiacloprid, and Clothianidin on the Growth and Development of Eisenia andrei

Recently, the high toxicity of neonicotinoids to the survival and reproduction of adult earthworms has become apparent in standard 56-day toxicity tests. The persistence of some neonicotinoids and/or their repeated application may lead to long-term exposure, possibly also affecting other parts of the life cycle of earthworms. The present study aimed at providing insight into the sublethal effects of imidacloprid, thiacloprid, and clothianidin on juvenile Eisenia andrei exposed for 16 weeks in Lufa 2.2 soil. Significant effects on growth and maturation were observed for all compounds. Exposure to 0.125 mg imidacloprid/kg dry soil and 0.03125 and 0.0625 mg thiacloprid/kg dry soil significantly affected the growth of the earthworms, while significant maturation effects were observed at 0.03125 mg/kg dry soil for imidacloprid and thiacloprid and 0.25 mg clothianidin/kg dry soil. The 16-week no-observed-effect concentrations (NOECs) found in the present study were lower than previously reported NOECs for effects on earthworm reproduction. Predicted environmental concentrations after a single application exceeded the observed NOECs for effects on earthworm maturation in the case of imidacloprid and thiacloprid and for effects on earthworm growth in the case of thiacloprid and clothianidin. Environ Toxicol Chem 2022;41:1686-1695. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

The impact of imidacloprid and thiacloprid on the mean species abundance in aquatic ecosystems

Neonicotinoids are currently the most widely used and sold insecticides in the world, providing effective pest control. Risk assessment of these and other pesticides by lab-based indicators is common. Yet, empirically and theoretically underpinning of extrapolation to indicators used in field surveys is severely limited. Consequently, the aim of our study was to quantify the toxicological and ecological impact of the neonicotinoids imidacloprid and thiacloprid to aquatic invertebrates. We derived Species Sensitivity Distributions (SSDs) based on chronic LC₅₀ data and Mean Species Abundance Relationships (MSARs), comparing these lab-based approaches to field data as well. MSARs are changes in mean species abundance (MSA) as a function of chemical exposure, providing insight into the overall decline of a community. The MSA expresses the mean abundance of species in disturbed conditions relative to their abundance in undisturbed habitat. The medians of the SSD of imidacloprid and thiacloprid for the different species were 16.45 μg/L and 26.40 μg/L, respectively. HC₅₀s of the MSAR of imidacloprid and thiacloprid were 4.25 μg/L and 5.12 μg/L, respectively. The three taxonomic groups tested (insects, crustaceans and mollusks) did not differ significantly in sensitivity for imidacloprid and thiacloprid, both according to the SSDs and MSARs derived. Quantile exposure-response curves (99%-tile) were plotted showing the relative abundance (RA) of aquatic invertebrate species at increasing imidacloprid levels. The 99%-tile of the Relative Abundances (RA₉₉) of species and corresponding imidacloprid concentrations monitored in field surveys in the Netherlands was significantly lower than the Potentially Affected Fraction (PAF) calculated from the SSD. Yet, the MSA was similar to the RA₉₉, suggesting that MSAR is an ecologically meaningful relationship for toxic stress estimated from lab data. Future efforts should be directed to additional empirical underpinning as well as determining the relationship of PAF to other metrics for ecosystem diversity and productivity.

Toxicogenomic profiling after sublethal exposure to nerve- and muscle-targeting insecticides reveals cardiac and neuronal developmental effects in zebrafish embryos

For specific primary modes of action (MoA) in environmental non-target organisms, EU legislation restricts the usage of active substances of pesticides or biocides. Corresponding regulatory hazard assessments are costly, time consuming and require large numbers of non-human animal studies. Currently, predictive toxicology of development compounds relies on their chemical structure and provides little insights into toxicity mechanisms that precede adverse effects. Using the zebrafish embryo model, we characterized transcriptomic responses to a range of sublethal concentrations of six nerve- and muscle-targeting insecticides with different MoA (abamectin, carbaryl, chlorpyrifos, fipronil, imidacloprid & methoxychlor). Our aim was to identify affected biological processes and suitable biomarker candidates for MoA-specific signatures. Abamectin showed the most divergent signature among the tested insecticides, linked to lipid metabolic processes. Differentially expressed genes (DEGs) after imidacloprid exposure were primarily associated with immune system and inflammation. In total, 222 early responsive genes to either MoA were identified, many related to three major processes: (1) cardiac muscle cell development and functioning (tcap, desma, bag3, hspb1, hspb8, flnca, myoz3a, mybpc2b, actc2, tnnt2c), (2) oxygen transport and hypoxic stress (alas2, hbbe1.1, hbbe1.3, hbbe2, hbae3, igfbp1a, hif1al) and (3) neuronal development and plasticity (npas4a, egr1, btg2, ier2a, vgf). The thyroidal function related gene dio3b was upregulated by chlorpyrifos and downregulated by higher abamectin concentrations. Important regulatory genes for cardiac muscle (tcap) and forebrain development (npas4a) were the most frequently ifferentially expressed across all insecticide treatments. We consider the identified gene sets as useful early warning biomarker candidates, i.e. for developmental toxicity targeting heart and brain in aquatic vertebrates. Our findings provide a better understanding about early molecular events in response to the analyzed MoA. Perceptively, this promotes the development for sensitive and informative biomarker-based in vitro assays for toxicological MoA prediction and AOP refinement, without the suffering of adult fish.

The Threat of Pests and Pathogens and the Potential for Biological Control in Forest Ecosystems

Forests are an essential component of the natural environment, as they support biodiversity, sequester carbon, and play a crucial role in biogeochemical cycles—in addition to producing organic matter that is necessary for the function of terrestrial organisms. Forests today are subject to threats ranging from natural occurrences, such as lightning-ignited fires, storms, and some forms of pollution, to those caused by human beings, such as land-use conversion (deforestation or intensive agriculture). In recent years, threats from pests and pathogens, particularly non-native species, have intensified in forests. The damage, decline, and mortality caused by insects, fungi, pathogens, and combinations of pests can lead to sizable ecological, economic, and social losses. To combat forest pests and pathogens, biocontrol may be an effective alternative to chemical pesticides and fertilizers. This review of forest pests and potential adversaries in the natural world highlights microbial inoculants, as well as research efforts to further develop biological control agents against forest pests and pathogens. Recent studies have shown promising results for the application of microbial inoculants as preventive measures. Other studies suggest that these species have potential as fertilizers.

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.

Long-term field-realistic exposure to a next-generation pesticide, flupyradifurone, impairs honey bee behaviour and survival

The assessment of pesticide risks to insect pollinators have typically focused on short-term, lethal impacts. The environmental ramifications of many of the world's most commonly employed pesticides, such as those exhibiting systemic properties that can result in long-lasting exposure to insects, may thus be severely underestimated. Here, seven laboratories from Europe and North America performed a standardised experiment (a ring-test) to study the long-term lethal and sublethal impacts of the relatively recently approved 'bee safe' butenolide pesticide flupyradifurone (FPF, active ingredient in Sivanto®) on honey bees. The emerging contaminant, FPF, impaired bee survival and behaviour at field-realistic doses (down to 11 ng/bee/day, corresponding to 400 µg/kg) that were up to 101-fold lower than those reported by risk assessments (1110 ng/bee/day), despite an absence of time-reinforced toxicity. Our findings raise concerns about the chronic impact of pesticides on pollinators at a global scale and support a novel methodology for a refined risk assessment.

Ecological risk assessment of pesticides in the Mijares River (eastern Spain) impacted by citrus production using wide-scope screening and target quantitative analysis

The widespread use of pesticides, especially in agricultural areas, makes necessary to control their presence in surrounding surface waters. The current study was designed to investigate the occurrence and ecological risks of pesticides and their transformation products in a Mediterranean river basin impacted by citrus agricultural production. Nineteen sites were monitored in three campaigns distributed over three different seasons. After a qualitative screening, 24 compounds was selected for subsequent quantitative analysis. As expected, the lower section of the river was most contaminated, with total concentration >5 µg/L in two sites near to the discharge area of wastewater treatment plants. The highest concentrations were found in September, after agricultural applications and when the river flow is reduced. Ecological risks were calculated using two mixture toxicity approaches (Toxic Unit and multi-substance Potentially Affected Fraction), which revealed high acute and chronic risks of imidacloprid to invertebrates, moderate-to-high risks of diuron, simazine and 2,4-D for primary producers, and moderate-to-high risks of thiabendazole for invertebrates and fish. This study shows that intensive agricultural production and the discharge of wastewater effluents containing pesticide residues from post-harvest citrus processing plants are threatening freshwater biodiversity. Further actions are recommended to control pesticide use and to reduce emissions.

Depletion kinetics and concentration- and time-dependent toxicity of a tertiary mixture of amitraz and its major hydrolysis products in honeybees

Although amitraz is one of the acaricides most commonly applied within beehives, to date, its time-dependent oral toxicity in honeybees has not been investigated, due to amitraz's instability in aqueous media. In aqueous media such as honey, amitraz rapidly forms a continuously changing tertiary mixture with two of its major hydrolysis products, DMF and DMPF. The contribution of each hydrolysis product to the overall oral toxicity of this acaricide is not known. Therefore, we aimed to characterize the depletion and formation kinetics of amitraz and its hydrolysis products in 50% sucrose solution provided to caged honeybees, including the calculation of the 50% lethal oral concentration (LC₅₀) of amitraz. We sought to determine the contribution of each component of the mixture to the overall observed toxicity. We also investigated the time- and concentration-dependent toxicity of the amitraz mixture and its hydrolysis products. A novel approach based on the analysis of the areas under the depletion and formation curves of amitraz and its hydrolysis products revealed that DMPF, amitraz and DMF accounted for 92%, 7% and 1% (respectively) of the overall toxicity of the mixture. The chronic oral LC₅₀ of amitraz was 3300 μmol/L, of similar magnitude as that of the non-toxic hydrolysis product DMF. The toxicity of DMPF and the mixture decreased over time; whereas the toxicity of DMF increased over time. Amitraz's instability in aqueous media and the highly toxic profile of DMPF, suggest that DMPF is the actual toxic entity responsible for amitraz's toxicity toward honeybees.

Concentration- and time-dependent toxicity of commonly encountered pesticides and pesticide mixtures to honeybees (Apis mellifera L.)

Honeybees are exposed to a wide range of pesticides for long periods via contaminated water, pollen and nectar. Some of those pesticides might constitute health hazards in a time- and dose-dependent manner. Time-dependent toxicity profiles for many applied pesticides are lacking, despite the fact that such profiles are crucial for toxicological evaluations. Therefore, we sought to determine the time-dependent toxicities of pesticides/pesticide metabolites frequently found in Israeli beehives, namely, amitraz metabolites, N'-(2,4-dimethylphenyl)-N-methylformamidine (DMPF) and N-(2,4-dimethylphenyl)-formamide (DMF), coumaphos, imidacloprid, thiacloprid, acetamiprid and dimethoate (toxic reference). By applying accepted methodological approaches such as the modified Haber's rule (product of concentration and exposure duration leads to a constant effect) and comparisons between cumulative doses at different time points, we determined the time-dependent toxicities of these pesticides. We also studied the mixture toxicities of frequently occurring pesticide combinations and estimated their potential contributions to the overall toxicities of neonicotinoids. Thiacloprid was the only pesticide that complied with Haber's rule. DMPF, dimethoate and imidacloprid exhibited time-diminished -toxicities. In contrast, DMF and acetamiprid exhibited time-reinforced toxicities. Neither the binary mixtures nor the tertiary mixtures of DMF, DMPF and coumaphos at 10 times their environmentally relevant concentrations potentiated the neonicotinoids' toxicities. DMPF and imidacloprid were found to present the greatest hazard to honeybees, based on their 50% lethal cumulative dose and 50% lethal time. Amitraz's instability, its low detection frequency and high toxicity profile of its metabolite, DMPF, lead us to the conclusion that DMPF constitutes the actual toxic entity responsible for amitraz's toxic effect.

Time-cumulative effects of neonicotinoid exposure, heatwaves and food limitation on stream mayfly nymphs: A multiple-stressor experiment

The global intensification of agriculture has resulted in pesticides playing an increasingly important role as anthropogenic stressors and drivers of environmental change. There is also a growing need to determine if other environmental stressors, especially those predicted to worsen with climate change, interact with pesticides to alter their effects on non-target biota. Two such stressors are increased extreme temperature events and periods of food limitation. This study is the first to investigate the combined effects of the world's most widely used insecticide, imidacloprid, with heatwaves and food limitation on a freshwater animal. A 6-week, full-factorial laboratory experiment with Deleatidium spp. mayfly nymphs was performed to investigate the potential for direct and delayed interactive effects of simulated heatwaves and starvation with chronic exposure to a field-realistic concentration of imidacloprid (0.4 μg/L). The experiment included two 6-day simulated heatwaves, one during a starvation period prior to imidacloprid addition, and one during the first 6 days of imidacloprid exposure. The simulated heatwaves alone caused such drastic negative effects on Deleatidium survival and mobility that mainly antagonistic interactions were observed with the other stressors, though delayed synergisms between imidacloprid and the second heatwave also affected mayfly mobility. Time-cumulative toxicity of imidacloprid was evident, with imidacloprid first affecting mayfly mobility after 12 days but eventually causing the strongest effects of all manipulated stressors. However, lethal effects of imidacloprid could only be detected in the absence of heatwaves and starvation, possibly as a result of selection for stronger individuals due to prior exposure to these stressors. Our findings demonstrate that heatwaves of increasing severity will critically affect sensitive freshwater organisms such as mayflies, and that the impacts of widespread pesticide use on freshwater ecosystems under global climate change cannot be ignored.

Similarities between pandemics and cancer in growth and risk models

Cancer and pandemics are leading causes of death globally, with severe socioeconomic repercussions. To better understand these repercussions, we investigate similarities between pandemics and cancer and describe the limited growth in number of infections or cancer cells, using mathematical models. For a pandemic, the analysis shows that in most cases, the initial fast growth is followed by a slower decay in the recovery phase. The risk of infection increases due to the airborne virus contact crossing a risk-threshold. For cancers caused by carcinogens, the increasing risk with age and absorbed dose of toxins that cross a risk-threshold, may lead to the disease onset. The time scales are different for both causes of death: years for cancer development and days to weeks for contact with airborne viruses. Contamination by viruses is on a time scale of seconds or minutes. The risk-threshold to get ill and the number-threshold in cancer cells or viruses, may explain the large variability in the outcome. The number of infected persons per day is better represented in log–lin plots instead of the conventional lin–lin plots. Differences in therapies are discussed. Our mathematical investigation between cancer and pandemics reveals a multifactorial correlation between both fragilities and brings us one step closer to understand, timely predict and ultimately diminish the socioeconomic hurdle of both cancer and pandemics.

The novel insecticides flupyradifurone and sulfoxaflor do not act synergistically with viral pathogens in reducing honey bee (Apis mellifera) survival but sulfoxaflor modulates host immunocompetence

The decline of insect pollinators threatens global food security. A major potential cause of decline is considered to be the interaction between environmental stressors, particularly between exposure to pesticides and pathogens. To explore pesticide-pathogen interactions in an important pollinator insect, the honey bee, we used two new nicotinic acetylcholine receptor agonist insecticides (nACHRs), flupyradifurone (FPF) and sulfoxaflor (SULF), at sublethal and field-realistic doses in a fully crossed experimental design with three common viral honey bee pathogens, Black queen cell virus (BQCV) and Deformed wing virus (DWV) genotypes A and B. Through laboratory experiments in which treatments were administered singly or in combination to individual insects, we recorded harmful effects of FPF and pathogens on honey bee survival and immune gene expression. Though we found no evidence of synergistic interactions among stressors on either honey bee survival or viral load, the combined treatment SULF and DWV-B led to a synergistic upregulation of dicer-like gene expression. We conclude that common viral pathogens pose a major threat to honey bees, while co-exposure to these novel nACHR insecticides does not significantly exacerbate viral impacts on host survival in the laboratory.

Evaluation of Systemic Imidacloprid and Herbicide Treatments on Flatheaded Borer (Coleoptera: Buprestidae) Management in Field Nursery Production

The flatheaded appletree borer, Chrysobothris femorata (Olivier) (Coleoptera: Buprestidae), and related species are deciduous tree pests. Female beetles prefer to oviposit at tree bases, and larvae tunnel beneath the bark, which weakens or kills young or newly transplanted trees. In the first objective of this study, Discus N/G (2.94% imidacloprid + 0.7% cyfluthrin) applied at six lower-than-labeled rates (0.0, 0.98, 1.97, 3.94, 5.91, and 7.87 ml/cm of average trunk dia.) was evaluated for protection of field-grown maples. A second objective evaluated imidacloprid with and without herbicides to assess the impact of weed competition at the tree base on insecticide effectiveness. A third objective determined relative imidacloprid concentrations in leaf tissue samples with ELISA and related to insecticide rates, herbicide treatments, and the level of flatheaded borer protection. In two trials, higher rates of insecticide were more effective at protecting trees, with rates ≥3.94 ml product/cm trunk diameter performing equivalently. Weed-free trees had more borer attacks and grew faster than trees in weedy plots. Imidacloprid content in leaf tissues had a trend for higher concentrations in smaller, weedy trees in the first season, but that pattern disappeared in subsequent years. Based on fewer attacks in weedy versus weed-free trees (60-90% reduction), it was concluded that weed presence can reduce borer attack success in nurseries independent of insecticide treatment, but tree growth was reduced by weed presence. In addition, Discus applied at rates >3.94 ml/cm did not confer added borer damage protection in weedy plots.

Evaluation of interregional consistency in associations between neonicotinoid insecticides and functions of benthic invertebrate communities in rivers in urban rice-paddy areas

Neonicotinoid insecticides pose risks that need to be managed for conservation of aquatic ecosystems. In this study, we evaluated the associations between the estimated environmental concentrations of two neonicotinoid insecticides (imidacloprid and dinotefuran) and the total abundances of seven functional feeding groups (FFGs) of benthic invertebrate communities in rivers in urban rice-paddy areas in four Japanese regions. Regional datasets of benthic invertebrate communities and environmental variables available for Japan were analyzed. The associations between neonicotinoid exposure and benthic functional groups in each region were evaluated by applying a partial redundancy analysis to each regional dataset. We then examined whether there was an interregionally consistent pattern in the observed associations to ascertain the general applicability of the associations. In two of the four regions, the associations of the total abundances of the seven FFGs with neonicotinoid concentrations were significant, suggesting negative effects of imidacloprid and dinotefuran on river ecosystem functions in these two Japanese regions. Moreover, although the associations in the remaining two regions were not significant, the pattern of associations of the total abundances of six of the FFGs (shredders, filter feeders, collectors, grazers, predators, and scavengers) with imidacloprid concentrations seemed to be consistent among the four regions. This implies broad-scale negative effects of imidacloprid on river ecosystem functions in urban rice-paddy areas. We did not, however, find any interregionally consistent patterns in the associations with dinotefuran concentrations. This may be related to the multicollinearity with the imidacloprid concentrations and/or the low maximum dinotefuran concentration relative to the toxicity values of this neonicotinoid. Therefore, the association between dinotefuran and river ecosystem functions requires additional investigation. We believe that this type of hypotheses-generating research using country-wide biomonitoring and exposure databases can be a great aid in future ecological risk assessment studies.

Molecular Basis for Endocrine Disruption by Pesticides Targeting Aromatase and Estrogen Receptor

The intensive use of pesticides has led to their increasing presence in water, soil, and agricultural products. Mounting evidence indicates that some pesticides may be endocrine disrupting chemicals (EDCs), being therefore harmful for the human health and the environment. In this study, three pesticides, glyphosate, thiacloprid, and imidacloprid, were tested for their ability to interfere with estrogen biosynthesis and/or signaling, to evaluate their potential action as EDCs. Among the tested compounds, only glyphosate inhibited aromatase activity (up to 30%) via a non-competitive inhibition or a mixed inhibition mechanism depending on the concentration applied. Then, the ability of the three pesticides to induce an estrogenic activity was tested in MELN cells. When compared to 17β-estradiol, thiacloprid and imidacloprid induced an estrogenic activity at the highest concentrations tested with a relative potency of 5.4 × 10⁻¹⁰ and 3.7 × 10⁻⁹, respectively. Molecular dynamics and docking simulations predicted the potential binding sites and the binding mode of the three pesticides on the structure of the two key targets, providing a rational for their mechanism as EDCs. The results demonstrate that the three pesticides are potential EDCs as glyphosate acts as an aromatase inhibitor, whereas imidacloprid and thiacloprid can interfere with estrogen induced signaling.

Long-term effects of neonicotinoid insecticides on ants

The widespread prophylactic usage of neonicotinoid insecticides has a clear impact on non-target organisms. However, the possible effects of long-term exposure on soil-dwelling organisms are still poorly understood especially for social insects with long-living queens. Here, we show that effects of chronic exposure to the neonicotinoid thiamethoxam on black garden ant colonies, Lasius niger, become visible before the second overwintering. Queens and workers differed in the residue-ratio of thiamethoxam to its metabolite clothianidin, suggesting that queens may have a superior detoxification system. Even though thiamethoxam did not affect queen mortality, neonicotinoid-exposed colonies showed a reduced number of workers and larvae indicating a trade-off between detoxification and fertility. Since colony size is a key for fitness, our data suggest long-term impacts of neonicotinoids on these organisms. This should be accounted for in future environmental and ecological risk assessments of neonicotinoid applications to prevent irreparable damages to ecosystems.