Neonicotinoids are globally used insecticides, and there are increasing evidence on their negative efects on birds. This study is aimed at characterizing the behavioral and physiological efects of the neonicotinoid imidacloprid (IMI) in a songbird. Adults of Agelaioides badius were exposed for 7 days to non-treated peeled millet and to peeled millet treated with nominal concentrations of 75 (IMI1) and 450 (IMI2) mg IMI/kg seed. On days 2 and 6 of the trial, the behavior of each bird was evaluated for 9 min by measuring the time spent on the foor, the perch, or the feeder. Daily millet consumption, initial and fnal body weight, and physiological, hematological, genotoxic, and biochemical parameters at the end of exposure were also measured. Activity was greatest on the foor, followed by the perch and the feeder. On the second day, birds exposed to IMI1and IMI2 remained mostly on the perch and the feeder, respectively. On the sixth day, a transition occurred to sec tors of greater activity, consistent with the disappearance of the intoxication signs: birds from IMI1 and IMI2 increased their time on the foor and the perch, respectively. Control birds always remained most of the time on the foor. IMI2 birds signifcantly decreased their feed intake by 31% the frst 3 days, compared to the other groups, and signifcantly decreased their body weight at the end of the exposure. From the set of hematological, genotoxic, and biochemical parameters, treated birds exhibited an alteration of glutathione-S-transferase activity (GST) in breast muscle; the minimal efects observed are probably related to the IMI administration regime. These results highlight that the consumption of less than 10% of the bird daily diet as IMI-treated seeds trigger efects at multiple levels that can impair bird survival. | Fil: Poliserpi, María Belén. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Recursos Biológicos; Argentina | Fil: Abad, Tatiana Noya. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Biológica; Argentina. Universidad Maimómides. Centro de Ciencias Naturales, Ambientales y Antropológicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina | Fil: De Gerónimo, Eduardo. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Balcarce; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. | Fil: Brodeur, Julie Céline. Consejo de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Recursos Biológicos. Argentina | Fil: Aparicio, Virginia Carolina. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Balcarce; Argentina

The recently recognized adverse environmental and toxic effects of neonicotinoid insecticides (NNIs) on non-target organisms are alarming. A comprehensive design, screening, and regulatory system was developed to generate NNI derivatives and mutant receptors with selective-ecotoxicological effects to overcome such adverse effects. For ligand design, taking ACE-09 derivative as an example, the toxicity on non-target animals (aboveground: bees; underground: earthworms), plant absorption, and soil absorption decreased by 4.80% and 13.7%, 10.0%, and 121%, while the toxicity on target animals (aboveground: aphids; underground: B. odoriphagas), plant metabolism, and soil degradation increased by 70.2% and 51.7%, 5.08%, and 8.28%. For receptor modification, the ability of mutants to absorb ACE-09 derivative decreased by 31.0%, while the ability of mutants to metabolize ACE-09 derivative increased by 28.0% in scenario 2 (mainly plant selectivity); the ability of mutants to degrade ACE-09 derivative increased by 11.6% in scenario 3 (mainly soil selectivity). The above results indicated that the selective-ecotoxicological effects of ligand design and receptor modification were both improved. Additionally, the combined effects of the ACE-09 derivative on plant absorption and metabolic mutants improved by 31.1% and 31.4% in scenario 2, respectively, while the effect on microbial degradation mutant improved by 14.9%, indicating that there was a synergistic effect between ligand design and receptor modification. Finally, based on the interaction between the ACE-09 derivative and mutants, the optimal environmental factors that improved the selectivity of their ecotoxicological effects were determined. For example, alternate application of nitrogen and phosphorus fertilizers effectively reduced the oxidative damage to plants caused by NNI residues. The novel ligand-receptor joint modification method, combined with the regulation of environmental factors under multiple scenarios, can biochemically address the ecotoxicological concern and highlight the harmful effects of pesticides on the environment and non-target organisms.

In developing countries, urban areas may be at greater risk of pesticide exposure compared to semi-urban agricultural regions. To investigate this, concentrations of selected pesticides were measured in 81 human milk samples collected in urban Kolkata and semi-urban Nadia in West Bengal, India. Three classes of pesticides were investigated – legacy organochlorines and emerging pyrethroids and neonicotinoids. The average concentration of the majority of the chemicals (DDT, its metabolites, HCH isomers, bifenthrin, endosulfan), showed a clear urban > semi-urban trend. Compared with previous measurements in other Indian cities and developing nations, current HCH and DDT concentrations in urban Kolkata were high. These chemicals were detected in 100% of the samples in both the urban and the semi-urban region. Also in both regions, the Estimated Daily Intake of DDTs, HCHs, aldrin, dieldrin and the pyrethroid bifenthrin for breastfed infants exceeded the Tolerable Daily Intake in a number of samples. Three pyrethroids were detected in human milk samples in India for the first time. This indicates a shift in the usage pattern of pesticides in India from organochlorines to pyrethroids. These findings may be used to drive targeted regulation of pesticides in developing countries with similar histories of pesticide use.

Studies have shown that the mixture toxicity of compounds with similar modes of action (MOAs) is usually predicted by the concentration addition (CA) model. However, due to the lack of toxicological information on compounds, more evidence is needed to determine whether the above conclusion is generally applicable. In general, the same type of compounds with similar chemical structures have similar MOAs, so whether the toxicities of the mixture of these compounds are additive needs to be further studied. In this paper, three types of pesticides with similar chemical structures (three organophosphoruses, two carbamates and two neonicotinoids) that may have similar MOAs were selected and five binary mixture systems were constructed. For each system, five mixture rays with different concentration ratios were designed by the direct equipartition ray design (EquRay) method. The mortality of Caenorhabditis elegans was regarded as the endpoint for the toxicity exposure to single pesticides and binary mixtures. The combined toxicities were evaluated simultaneously using the CA model, isobologram and combination index. The structural similarity of the same type of pesticides was quantitatively analyzed according to the MACCS molecular fingerprint and the slope of dose-response curve at pEC₅₀. The results show that the toxicities of neonicotinoid mixtures and carbamate mixtures are almost antagonistic. The entire mixture system of dichlorvos and dimethoate produced synergism, and four of the five mixture rays of dimethoate and methamidophos induced antagonism, while among the mixture rays of dichlorvos and methamidophos, different concentrations showed different interaction types. The results of structural similarity analysis show that the size of structural similarity showed a certain quantitative relationship with the toxicity interaction of mixtures, that is, the structural similarity of the same type of pesticides may show an additive action in a certain range.

The occurrence and spatial distribution of selected pesticides were investigated along a 200-km reach of the St. Lawrence River (SLR) and tributaries in Quebec, Canada. Surface water samples (n = 68) were collected in the summer 2017 and analyzed for glyphosate, atrazine (ATZ), 8 systemic insecticides (acetamiprid, clothianidin, dinotefuran, fipronil, imidacloprid, nitenpyram, thiacloprid, and thiamethoxam) and some metabolites. Overall, 99% of the surface water samples were positive to at least one of the targeted pesticides. The most recurrent compounds were glyphosate (detection frequency: 84%), ATZ (82%), thiamethoxam (59%), desethylatrazine (DEA: 47%), and clothianidin (46%). Glyphosate displayed variable levels (4–3,000 ng L−1), with higher concentrations in south tributaries (e.g., Nicolet and Yamaska). In positive samples, the sum of ATZ and DEA varied between 5 and 860 ng L−1, and the sum of 6 priority neonicotinoids between 1.5 and 115 ng L−1. From Repentigny to the Sorel Islands, the spatial distribution of pesticides within the St. Lawrence River was governed by the different upstream sources (i.e., Great Lakes vs. Ottawa River) due to the limited mixing of the different water masses. Cross-sectional patterns revealed higher concentrations of glyphosate and neonicotinoids in the north portions of transects, while the middle and south portions showed higher levels of atrazine. In Lake St. Pierre and further downstream, cross-sections revealed higher levels of the targeted pesticides near the southern portions of the SLR. This may be due to the higher contributions from south shore tributaries impacted by major agricultural areas, compared to north shore tributaries with forest land and less cropland use. Surface water samples were compliant with guidelines for the protection of aquatic life (chronic effects) for glyphosate and atrazine. However, 31% of the samples were found to surpass the guideline value of 8.3 ng L−1 for the sum of six priority neonicotinoids.

Neonicotinoids pollution poses a serious threat to aquatic ecosystems. However, there is currently little knowledge about how neonicotinoids are transferred from the agricultural environment to the aquatic environment. Here, we conducted in situ high-frequency monitoring of neonicotinoids in soil-water systems along the hydrological flow path during rainfall to explore the horizontal and vertical transport mechanisms of neonicotinoids. The collected samples included 240 surface runoff, 128 subsurface runoff, 60 eroded sediment, 120 soil and 144 soil solution, which were used to analyse neonicotinoids concentrations. Surface runoff, subsurface runoff and eroded sediment were the three main paths for the horizontal migration of neonicotinoids. In the CK (citrus orchards without grass cover) and grass-covered citrus orchards, there are 15.89% and 2.29% of the applied neonicotinoids were transported with surface runoff, respectively. While in the CK and grass-covered citrus orchards, there are only 1.23% and 0.19% of the applied neonicotinoids were transported with eroded sediment and subsurface runoff. Although the amount of neonicotinoids lost along with eroded sediment was small, the concentration of neonicotinoids in eroded sediment was two orders of magnitude higher than the concentration of neonicotinoids in sediments of the surface water. Meanwhile, neonicotinoids migrated vertically in soil due to water infiltration. In the CK and grass-covered citrus orchards, there are 57.64% and 24.36% of the applied neonicotinoids were retained in soil and soil solution, respectively, and their concentration decreased as soil depth increased. Another noteworthy phenomenon is that more neonicotinoids migrated to deeper soil layers under grass cover compared with no grass cover because grass roots promoted the formation of cracks and vertical preferential flow. Our results are expected to improve the accuracy of neonicotinoids pollution prediction by considering migration paths, including surface and subsurface runoff and eroded sediment.

Municipal sewage treatment plants (STPs) have been regarded as an important source of organic contaminants in aquatic environment. To assess the impact of STPs on occurrence and toxicity of STP-associated contaminants in receiving waterways, a novel passive sampler modified from polar organic chemical integrative sampler (m-POCIS) was deployed at the inlet and outlet of a STP and several upstream and downstream sites along a river receiving STP effluent in Guangzhou, China. Eighty-seven contaminants were analyzed in m-POCIS extracts, along with toxicity evaluation using zebrafish embryos. Polycyclic musks were the predominant contaminants in both STP and urban waterways, and antibiotics and current-use pesticides (e.g., neonicotinoids, fiproles) were also ubiquitous. The m-POCIS extracts from downstream sites caused significant deformity in embryos, yet the toxicity could not be explained by the measured contaminants, implying the presence of nontarget stressors. Sewage treatment process substantially reduced embryo deformity, chemical oxygen demand, and contamination levels of some contaminants; however, concentrations of neonicotinoids and fiproles increased after STP treatment, possibly due to the release of chemicals from perturbed sludge. Source identification showed that most of the contaminants found in urban waterways were originated from nonpoint runoff, while cosmetics factories and hospitals were likely point sources for musks and antibiotics, respectively. Although the observed embryo toxicity could not be well explained by target contaminants, the present study showed a promising future of using passive samplers to evaluate chemical occurrence and aquatic toxicity concurrently. Zebrafish embryo toxicity significantly decreased after sewage treatment, but higher toxicity was observed for downstream samples, demonstrating that urban runoff may produce detrimental effects to aquatic life, particularly in rainy season. These results highlight the relevance of monitoring nonpoint source pollution along with boosting municipal sewage treatment infrastructure.

Seed coating (‘seed treatment’) is the leading delivery method of neonicotinoid insecticides in major crops such as soybean, wheat, cotton and maize. However, this prophylactic use of neonicotinoids is widely discussed from the standpoint of environmental costs. Growing soybean plants from neonicotinoid-coated seeds in field, we demonstrate that soybean aphids (Aphis glycines) survived the treatment, and excreted honeydew containing neonicotinoids. Biochemical analyses demonstrated that honeydew excreted by the soybean aphid contained substantial concentrations of neonicotinoids even one month after sowing of the crop. Consuming this honeydew reduced the longevity of two biological control agents of the soybean aphid, the predatory midge Aphidoletes aphidimyza and the parasitic wasp Aphelinus certus. These results have important environmental and economic implications because honeydew is the main carbohydrate source for many beneficial insects in agricultural landscapes.

Exploring traditional neonicotinoid pesticides substitutes has become one of the global scientific attentions because of their hazardous environmental impacts. Cycloxaprid (CYC) is considered to be a promising candidate alternative. But the environmental behaviors and fate of CYC in different planting system remain poorly understood. The accumulation of 14C-labeled CYC stereoisomers within different parts of Chinese cabbage (Brassica chinensis L.) was investigated, with a particular focus on the foliar absorption, translocation and stereoselectivity of CYC, during a laboratory trial. In general, the stereoisomers 14C-5R,8S-CYC and 14C-5S,8R-CYC, their metabolites, as well as the breakdown and reaction products can be transferred in both acropetal and basipetal directions. Most of the two stereoisomers absorbed by plants remained in the treated leaves, whereas a small amount was distributed to the roots. The amount of 14C in the stalks varied among the experimental time points. At 192 h after treatment (HAT), the detected radioactivity of both 14C-5R,8S-CYC and 14C-5S,8R-CYC in the leaves above the treated leaf (LATL) was higher than that in the leaves below the treated leaf (LBTL). However, the stereoisomers of CYC underwent nonstereoselective absorption and translocation in this trial. This information implies that racemic CYC and its metabolites should be a main research focus. Thus, the obtained results provide implications for a more accurate prediction about the risk assessment of CYC, which will be helpful for guiding its rational use as well as securing the ecological environment safety and human health.

Due to their systemic character and high efficacy to insect controls, neonicotinoid insecticides (neonics) have been widely used in global agriculture since its introduction in early 1990. Recent studies have indicated that neonics may be ubiquitous, have longer biological half-lives in the environment once applied, and therefore implicitly suggested the increasing probability for human exposure to neonics. Despite of neonics’ persistent characters and widespread uses, scientific literature in regard of pathways in which human exposure could occur is relatively meager. In this review, we summarized results from peer-reviewed articles published prior to 2017 that address potential human exposures through ingestion and inhalation, as well as results from human biomonitoring studies. In addition, we proposed the use of relative potency factor approach in order to facilitate the assessment of concurrent exposure to a mixture of neonics with similar chemical structures and toxicological endpoints. We believe that the scientific information that we presented in this review will aid to future assessment of total neonic exposure and subsequently human health risk characterization.