An overview of pyrethroid insecticides

Alkylsulfones: novel chemical scaffolds targeting the vesicular acetylcholine transporter usher in a new generation of insecticides

Insecticides targeting the nervous system have been the most widely used to control arthropod pests due to their fast onset of action leading to efficient crop protection. With their continued use, resistance has and will become an inevitable challenge that demands continued efforts in identifying and developing new insecticidal chemistries acting on novel targets. In a recent publication, the results of a comprehensive study investigating the mode of action of novel chemical scaffolds based on the 2-(3-ethylsulfonyl-2-pyridyl)-heterocycles, alkylsulfones, was presented, concluding that their primary target is the vesicular acetylcholine transporter. © 2024 Society of Chemical Industry.

A scoping review to determine if adverse human health effects are associated with use of pyrethroids for mosquito control

Mosquito control using pyrethrins and synthetic pyrethroids (PSP) is important for preventing vector-borne diseases. Although the benefits associated with PSP use are well-documented, public concern exists regarding potential human adverse health effects. The aim of this scoping review was to describe adverse human health effects associated with PSP use for community adult mosquito control. A literature search using the databases MEDLINE, EMBASE, Agricultural and Environmental Science Collection, CAB Abstracts, and Scopus obtained 6,154 original peer-reviewed articles published during 1 January 2000 to 22 May 2024. Articles were independently reviewed for inclusion using predetermined exclusion and inclusion criteria. Data were extracted from 10 included articles. Study designs included cohort (n = 5), cross-sectional (n = 2), and risk assessment (n = 4). One article included 2 study designs. Of the cohort studies, one was prospective and the remainder were retrospective. A causal relationship between PSP application for adult mosquito control and adverse human health impacts was not identified. No increases in acute health manifestations were reported. The 4 risk assessments estimated that PSP exposures were not above the regulatory level of concern; a meta-analysis determined the likelihood of PSP exposures exceeding the regulatory level of concern was <0.0001. The limited evidence indicated that PSP applied appropriately for control of nuisance mosquitoes or mosquitoes that transmit arboviruses do not pose acute or chronic human health risks. Continued investigation into potential human health impacts of PSP would help inform guidelines for adult mosquito control and help inform public health decision making.

Bifenthrin causes disturbance in mitochondrial dynamics and bioenergetic system in human embryonic kidney cells (HEK 293)

Synthetic pyrethroids (SPs) such as bifenthrin (BF) have been used worldwide in pest control due to their high insecticidal activity and low toxicity to mammals. However, due to their lipophilicity, BF can persist in various environments and cause significant adverse effects on non-target organisms, including humans. Mitochondria, crucial for cellular energy production and homeostasis, are primary targets of environmental toxins like BF. This study, which investigated the impact of BF on mitochondrial function in human embryonic kidney (Hek 293) cells, found that BF caused cytotoxicity via a reduction in cell viability assessed by the MTT assay and triggered apoptosis in cells characterized by nuclear condensation and formation of apoptotic bodies revealed through the AO/PI study. BF exposure also led to a marked increase in reactive oxygen species (ROS) levels and a significant reduction in mitochondrial membrane potential (MMP), indicating oxidative stress and mitochondrial dysfunction. BF treatment concentration of 1.00 μM and 2.00 μM significantly affects mitochondrial respiratory capacity by lowering the basal and maximal respiration, ATP production, and spare respiratory capacity, leading to mitochondrial impairment. Gene expression analysis also showed BF exposure altered the expression of genes related to mitochondrial fusion (MFN1, MFN2, OPA1) and fission (FIS1, DRP1), suggesting a disruption in the balance of mitochondrial dynamics. Defects in mitochondrial dynamics caused fragmentation of the mitochondrial branch length and number in BF induced cell compared to control. The analysis of mRNA expression of apoptosis genes also indicated that BF induced cell death. This study demonstrated that BF induced cytotoxicity disrupted mitochondrial membrane potential and impaired mitochondrial bioenergetics. Therefore, this finding emphasizes the significance of understanding the impact of BF on mitochondrial function, highlighting the need for further research and action to mitigate the potential long-term human health risks associated with this pesticide.

Application of the Integrated Approach to Testing and Assessment (IATA) for evaluating endocrine disruption potential of selected pyrethroids by H295R steroidogenesis and ER/AR transcriptional activation

Pyrethroids, which are widely utilized in agriculture, household products, and public health for their potent insecticidal properties, elicit significant concerns regarding their potential endocrine-disrupting effects. However, previous studies have yielded inconsistent data, largely due to the absence of a standardized screening system. To address this limitation, the present study introduces an Integrated Approach to Testing and Assessment (IATA) to evaluate the endocrine-disrupting potential of pyrethroids, aligned with the Adverse Outcome Pathway (AOP) framework. Employing this IATA-based methodology, the endocrine-disrupting effects of five pyrethroids, allethrin, phenothrin, deltamethrin, cypermethrin, and lambda-cyhalothrin-were investigated, with a focus on hormone levels of 17β-estradiol (E2) and testosterone (T). Enzyme-linked immunosorbent assays (ELISA) and receptor transactivation assays were utilized to assess the direct receptor interactions and alternative disruption mechanisms. The results demonstrated that lambda-cyhalothrin and phenothrin significantly elevated E2 levels, while all tested compounds substantially reduced T levels. Notably, transactivation assays indicated that these pyrethroids function as estrogenic agonists and androgenic antagonists, suggesting their complex role in endocrine disruption. The IATA-based framework, incorporating steroidogenesis and receptor transactivation assays, provides a comprehensive approach for assessing endocrine disruption, enabling the early identification and prioritization of hazardous chemicals. By predicting adverse outcomes without relying on in vivo testing, this integrated approach enhances regulatory decision making, promotes public health protection, and supports ethical and efficient chemical risk assessment.

Role of Lactic Acid Bacteria in Insecticide Residue Degradation

Lactic acid bacteria are gaining global attention, especially due to their role as a probiotic. They are increasingly being used as a flavoring agent and food preservative. Besides their role in food processing, lactic acid bacteria also have a significant role in degrading insecticide residues in the environment. This review paper highlights the importance of lactic acid bacteria in degrading insecticide residues of various types, such as organochlorines, organophosphorus, synthetic pyrethroids, neonicotinoids, and diamides. The paper discusses the mechanisms employed by lactic acid bacteria to degrade these insecticides, as well as their potential applications in bioremediation. The key enzymes produced by lactic acid bacteria, such as phosphatase and esterase, play a vital role in breaking down insecticide molecules. Furthermore, the paper discusses the challenges and future directions in this field. However, more research is needed to optimize the utilization of lactic acid bacteria in insecticide residue degradation and to develop practical strategies for their implementation in real-world scenarios.

Binary Mixture of Neonicotinoid-Pyrethroid Insecticide: Impact on Survival, Cognitive Learning, and Memory in Apis mellifera jemenitica

The impact of agrochemicals on pollinators, especially honey bees, has drawn significant attention due to its critical implications for worldwide food stability and ecosystems. Given the potential threat of insecticides to honey bees, bees may encounter multiple insecticides simultaneously during foraging. This study investigated the toxic effect of an insecticide mixture (IM) containing acetamiprid (neonicotinoid) and deltamethrin (pyrethroid) on the survival and cognitive appetitive performance of Apis mellifera jemenitica, a vital native pollinator in arid regions of Saudi Arabia. The lethal concentration (LC50) was determined by assessing bees' mortality rates following exposure to IM through topical and oral routes. Significant bee mortality occurred at 4-48 h post treatment with IM through both exposure routes, showing a trend of increased mortality with higher IM concentrations compared to the control bees. Throughout all tested times, topical exposure proved relatively more effective, resulting in significantly greater bee mortality compared to oral exposure to IM. Food intake declined progressively with rising IM concentrations during oral exposure. The LC50 values of IM at 24 h after treatment were 12.24 ppm for topical and 10.45 ppm for oral exposure. The corresponding LC10, LC20, and LC30 values were 3.75 ppm, 5.63 ppm, and 7.54 ppm for topical exposure and 2.45 ppm, 4.04 ppm, and 5.78 ppm for oral exposure, respectively. The combination index (CI) revealed a synergistic effect (0.43) for topical exposure and antagonistic effects (1.43) for oral exposure, highlighting differential toxicity dynamics. IM exposure significantly impaired cognitive acquisition and memory reinforcement in honey bees, as demonstrated through behavioral assays, indicating potential neurotoxic effects. Learning and memory formation significantly declined at 2, 12, and 24 h after exposure to sublethal concentrations of IM through both topical and oral routes. Thus, evaluating the interactive impact of multiple pesticides on bees' health and cognitive function is essential, particularly in regions where diverse agrochemicals are routinely utilized.

An Assessment of the Cyto-Genotoxicity Effects of Green-Synthesized Silver Nanoparticles and ATCBRA Insecticide on the Root System of Vicia faba

We aimed to synthesize silver nanoparticles (AgNPs) using Elettaria cardamomum (cardamom) extracts and assess the cytotoxicity and genotoxicity of the cardamom extract, cardamom-AgNPs, and the insecticide ATCBRA-commonly used for pest control-on the root system of Vicia faba (broad bean). The chemical composition of the aqueous cardamom extract was identified and quantified using GC-MS, revealing a variety of bioactive compounds also present in cardamom essential oil. These included α-terpinyl acetate (21.3-44.3%), 1,8-cineole (10.7-28.4%), and linalool (6.4-8.6%). The successful green synthesis of AgNPs was confirmed through various micro-spectroscopic techniques, including UV-Vis spectroscopy, transmission electron microscopy (TEM), and energy-dispersive spectroscopy (EDS). UV-Vis analysis showed a strong peak between 420 and 430 nm, indicating the presence of AgNPs. TEM imaging revealed that the synthesized cardamom-AgNPs were monodispersed, primarily spherical, and semi-uniform in shape, with minimal aggregation. EDS analysis further confirmed the composition of the nanoparticles, with cardamom-AgNPs comprising around 60.5% by weight. Cytotoxicity was evaluated by measuring the mitotic index (MI), and genotoxicity was assessed by observing chromosomal aberrations (CAs). The roots of Vicia faba were treated for 24 and 48 h with varying concentrations of ATCBRA pesticide (0.1%, 0.3%, 0.5%, and 0.7%), aqueous cardamom extract (3%, 4%, 5%, and 6%), and green-synthesized cardamom-AgNPs (12, 25, and 60 mg). The cytogenetic analysis of MI and CA in the meristematic root tips indicated an improvement in the evaluated parameters with the cardamom extract. However, a marked reduction in mitotic activity was observed with both ATCBRA and cardamom-AgNP treatments across both time points, highlighting potential cytotoxic and genotoxic effects.

Physiologically based toxicokinetic and toxicodynamic (PBTK-TD) modelling of cis-bifenthrin in Carassius auratus and Xenopus laevis accounting for reproductive toxicity

Pyrethroid insecticides are a class of endocrine disruptors and are believed to exhibit reproductive toxicity to aquatic organisms. Pyrethroids are widely detected in aquatic environments and can accumulate in aquatic organisms, but studies on their accumulation and the associated reproductive toxicity in aquatic organisms are still limited. We utilized Carassius auratus and Xenopus laevis as models for fish and amphibians, respectively, and developed and validated a physiologically based toxicokinetic and toxicodynamic (PBTK-TD) model for adult fish and frogs exposed to typical pyrethroid pesticides cis-bifenthrin (cis-BF). The model includes the brain, kidney, liver, gonads, gills/lungs, well-perfused tissue, and poorly-perfused tissue, which are interconnected by blood circulation in the PBTK process. There are also dynamic relationships between target organ concentrations and reproductive-related endpoints in the TD process. Results showed that the PBTK sub-model accurately described and predicted the uptake, distribution, and disposition kinetics in fish and frogs. In fish, the kidney exhibited the fastest accumulation rate, while in frogs, the skin showed the fastest accumulation rate, followed by the kidney. Sensitivity analysis indicated that parameters such as blood flow and blood distribution coefficients had significant effects on chemical concentrations. A sigmoid Emax model was employed to describe the relationship between the reproductive toxicity effects of cis-BF and its dose-concentration variations. We found that testosterone (T) exhibited the highest correlation coefficient, suggesting that T could serve as an effective biomarker for cis-BF reproductive toxicity. The PBTK-TD model established in this study is beneficial for predicting the toxicological effects of pyrethroids in fish and amphibians.

The Potential of Agaricus bisporus in Mitigating Pesticide-Induced Oxidative Stress in Honey Bees Infected with Nosema ceranae

Global climate change, environmental pollution, and frequent pesticide use severely reduce bee populations, greatly challenging beekeeping. Pesticides such as deltamethrin, a pyrethroid insecticide commonly used to control mosquitoes, can kill individual bees and entire colonies, depending on the exposure. Due to mosquito resistance to pyrethroid insecticides, components that enhance their effect are commonly used. This study explores the potential of Agaricus bisporus mushroom extract in mitigating oxidative stress in bees triggered by pesticides and Nosema ceranae infection. Our findings indicate that A. bisporus extract significantly reduced mortality rates of bees and spore counts of N. ceranae. Furthermore, the extract demonstrated antioxidant properties that lower enzyme activity related to oxidative stress (CAT, SOD, and GST) and MDA concentration, which is linked to lipid peroxidation. These results indicate that natural extracts like A. bisporus can aid bee health by mitigating the effects of pesticides and pathogens on honey bees, thus improving biodiversity.

Quantitative measures of recent and lifetime agricultural pesticide use are associated with increased pesticide concentrations in house dust

OBJECTIVE

Elevated pesticide concentrations have been found in dust from homes with residents who use agricultural pesticides, but few studies have compared these concentrations to quantitative measures of their use. We evaluated household pesticide dust concentrations in relation to quantitative, active ingredient-specific metrics of agricultural pesticide use in the Biomarkers of Exposure and Effect in Agriculture Study.

METHODS

Participants provided vacuum dust samples (2013-2018) and information regarding recent (last 12 months) and lifetime pesticide use. Thirty-two pesticide analytes were measured in 295 dust samples from 213 participants; 54 had repeated measurements (median = 96 days between visits). We used mixed-effects quantile regression models to estimate relative differences in pesticide concentrations for recent and lifetime agricultural use (number of days, intensity-weighted days), recent home/garden use (yes/no), and household characteristics. Only household characteristics were examined for dacthal because of no use information. We calculated intraclass correlation coefficients (ICCs) to evaluate temporal variability. We report only descriptive statistics for pesticides with detection rates <25 %.

RESULTS

For currently used pesticides, quantitative measures of recent agricultural use were associated with significantly increased household pesticide dust concentrations for malathion, metolachlor, acetochlor, cyfluthrin, and atrazine (p-trends < 0.001), but not permethrin. Similarly, quantitative measures of lifetime use were associated with increased concentrations of malathion, metolachlor, carbaryl, diazinon, and atrazine (p-trends < 0.001), but not permethrin, chlorpyrifos, or chlorothalonil. For banned pesticides, ever agricultural use was associated with elevated chlordane and heptachlor concentrations and non-significantly elevated dieldrin concentrations, but not lindane, p,p-DDD, p,p-DDE, or p,p-DDT. Recent home/garden use predicted increased malathion, carbaryl, and cyfluthrin concentrations. ICCs (range = 0.57-0.90) suggested moderate to high correlation over 3-6 months. Detection rates were <25 % for alachlor, butylate, EPTC, metribuzin, simazine, carbofuran, coumaphos, as well as for three banned pesticides (cyanazine, aldrin, endosulfan).

CONCLUSIONS

Household pesticide dust concentrations were strongly associated with the frequency of agricultural pesticide use.

Assessment of non-target toxicity of insecticides on Ganaspis brasiliensis (Ihering) in laboratory and field conditions

BACKGROUND

G1 strain Ganaspis brasiliensis (Ihering) has been recently released in both Europe and America as a biological control agent of the spotted wing drosophila, Drosophila suzukii (Matsumura). In initial phases of classical biological control programs, it becomes imperative to evaluate the susceptibility of parasitoids to insecticides, to identify the best alternatives to adopt in an integrated pest management and organic perspective. In this study, we evaluated lethal and sublethal effects of topical application of five different insecticides classes: neonicotinoids, diamides, pyrethroids, organophosphates and spinosyns. Additionally, we tested residual toxicity in field trials in vineyards and sweet cherry orchards.

RESULTS

Adult wasps' susceptibility to different insecticides' classes were consistent between laboratory and field. Spinosad exhibited the highest toxicity, with a median lethal concentration (LC50) of 0.00372 of the maximum field dose, and the highest knock-down effect in field trials, causing 92.5 ± 5% of mortality at T0. λ-cyhalothrin showed sublethal effects on both male and female insects' longevity when applied at LC30. In field trials, deltamethrin showed the highest persistence, causing significant parasitoid mortality up to 14 days after treatment. Conversely, cyantraniliprole was the least toxic active ingredient according to both topical and residual bioassays, even though its residues caused mortality up to 7 days after the treatment in the field.

CONCLUSION

Our results indicate that spinosad and λ-cyhalothrin are highly toxic to G. brasiliensis, making them incompatible with classical biological control programs. Cyantraniliprole exhibited lower toxicity, and may be considered a selective pesticide for the integrated management of D. suzukii. © 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

The ability of selected fungal strains to produce carboxylesterase enzymes for biodegradation and use of bifenthrin insecticide as carbon source: in vitro and in silico approaches

Bifenthrin (BF) is a broad-spectrum type I pyrethroid insecticide that acts on insects by impairing the nervous system and inhibiting ATPase activity, and it has toxic effects on non-target organisms and high persistence in the environment. This study aimed to determine the potential of six different fungi, including Pseudozyma hubeiensis PA, Trichoderma reesei PF, Trichoderma koningiopsis PD, Purpureocillium lilacinum ACE3, Talaromyces pinophilus ACE4, and Aspergillus niger AJ-F3, to degrade BF. Three different concentrations of BF, including 0.1%, 0.2%, and 0.3% w/v, were used in the sensitivity testing that revealed a significant (p ≤ 0.01) impact of BF on fungal growth. Enzymatic assays demonstrated that both intracellular and extracellular carboxylesterases hydrolyzed BF with the enzymatic activity of up to 175 ± 3 U (μmol/min) and 45 ± 1 U, respectively. All tested fungi were capable of utilizing BF as a sole carbon source producing 0.06 ± 0.01 to 0.45 ± 0.01 mg dry biomass per mg BF. Moreover, the presence of PytH was determined in the fungi using bioinformatics tools and was found in A. niger, T. pinophilus, T. reesei, and P. lilacinum. 3D structures of the PytH homologs were predicted using AlphaFold2, and their intermolecular interactions with pyrethroids were determined using MOE. All the homologs interacted with different pyrethroids with a binding energy of lesser than - 10 kcal/mol. Based on the study, it was concluded that the investigated fungi have a greater potential for the biodegradation of BF.

Combining QSAR and SSD to predict aquatic toxicity and species sensitivity of pyrethroid and organophosphate pesticides

The widespread use of pyrethroid and organophosphate pesticides necessitates accurate toxicity predictions for regulatory compliance. In this study QSAR and SSD models for six pyrethroid and four organophosphate compounds using QSAR Toolbox and SSD Toolbox have been developed. The QSAR models, described by the formula 48 h-EC50 or 96 h-LC50 = x + y * log Kow, were validated for predicting 48 h-EC50 values for acute Daphnia toxicity and 96 h-LC50 values for acute fish toxicity, meeting criteria of n ≥10, r2 ≥0.7, and Q2 >0.5. Predicted 48 h-EC50 values for pyrethroids ranged from 3.95 × 10-5 mg/L (permethrin) to 8.21 × 10-3 mg/L (fenpropathrin), and 96 h-LC50 values from 3.89 × 10-5 mg/L (permethrin) to 1.68 × 10-2 mg/L (metofluthrin). For organophosphates, 48 h-EC50 values ranged from 2.00 × 10-5 mg/L (carbophenothion) to 3.76 × 10-2 mg/L (crufomate) and 96 h-LC50 values from 3.81 × 10-3 mg/L (carbophenothion) to 12.3 mg/L (crufomate). These values show a good agreement with experimental data, though some, like Carbophenothion, overestimated toxicity. HC05 values, indicating hazardous concentrations for 5% of species, range from 0.029 to 0.061 µg/L for pyrethroids and 0.030 to 0.072 µg/L for organophosphates. These values aid in establishing environmental quality standards (EQS). Compared to existing EQS, HC05 values for pyrethroids were less conservative, while those for organophosphates were comparable.

Placental transcriptome variation associated with season, location, and urinary prenatal pyrethroid metabolites of Thai farm-working women

Prenatal exposure to pyrethroids is linked to adverse health effects in early life and proper placental function is critical to fetal development. This study explores the impact of prenatal pyrethroid exposure, as well as factors impacting exposure and effect, on the placental transcriptome, to understand pyrethroid exposures' relationship to placental function. The study of Asian Women and their Offspring's Development and Environmental Exposures (SAWASDEE) recruited pregnant farm-working women from two agricultural districts in the Chiang Mai province of Thailand between 2017 and 2019. This cohort was predominantly exposed to cypermethrin (type II), alongside pyrethroids such as cyfluthrin (type II) and permethrin (type I). In 253 participants, maternal urinary pyrethroid metabolites, 3-phenoxybenzoic acid (PBA), cis-3-(2,2-Dichlorovinyl)-2,2-dimethylcyclopropane carboxylic acid (CDCCA), and trans-3-(2,2-Dichlorovinyl)-2,2-dimethylcyclopropane carboxylic acid (TDCCA) were measured in early, middle, and late pregnancy and adjusted for urinary creatinine. The placental transcriptome was analyzed using RNA-Seq. Using generalized linear regression, we identified differentially expressed genes (DEGs) associated with the sum of each metabolite across pregnancy, as well as those associated with location of residence and season of birth. Pathway and upstream transcription factor analyses were performed to examine potential mechanisms associated with DEGs. Notably, TDCCA and CDCCA levels peaked in late pregnancy, with significant regional differences, particularly higher levels in the Fang region. Placental gene expression analysis showed no DEGs associated with individual metabolites at FDR<0.05. However, 251 DEGs by location, implicating immune response and oxidative phosphorylation pathways, were identified, while season of birth was associated with 2585 DEGs, over-represented in fibrosis signaling and metabolism pathways. Finally, transcription factor analysis identified 226 and 282 transcription factors associated with location and season, respectively, related to cell proliferation, differentiation, and the immune system. These alterations may have significant implications for fetal development and other pathologic processes, highlighting the importance of monitoring environmental exposures during pregnancy.

Exploring the link between pyrethroids exposure and dopaminergic degeneration through morphometric, immunofluorescence, and in-silico approaches: the therapeutic role of chitosan-encapsulated curcumin nanoparticles

Introduction: The synthetic pyrethroid derivative fenpropathrin (FNE), a commonly used insecticide, has been associated with various toxic effects in mammals, particularly neurotoxicity. The study addressed the hallmarks of the pathophysiology of Parkinson's disease upon oral exposure to fenpropathrin (FNE), mainly the alteration of dopaminergic markers, oxidative stress, and molecular docking in rat models. In addition, the protective effect of curcumin-encapsulated chitosan nanoparticles (CRM-Chs-NPs) was also assessed. Methods: In a 60-day trial, 40 male Sprague Dawley rats were divided into 4 groups: Control, CRM-Chs-NPs (curcumin-encapsulated chitosan nanoparticles), FNE (15 mg/kg bw), and FNE + CRM-Chs-NPs. Results: FNE exposure induced reactive oxygen species generation, ATP production disruption, activation of inflammatory and apoptotic pathways, mitochondrial function and dynamics impairment, neurotransmitter level perturbation, and mitophagy promotion in rat brains. Molecular docking analysis revealed that FNE interacts with key binding sites of dopamine synthesis and transport proteins. On the other hand, CRM-Chs-NPs mitigated FNE's toxic effects by enhancing mitochondrial dynamics, antioxidant activity, and ATP production and promoting anti-inflammatory and antiapoptotic responses. Conclusion: In summary, FNE appears to induce dopaminergic degeneration through various mechanisms, and CRM-Chs-NPs emerged as a potential therapeutic intervention for protecting the nervous tissue microenvironment.

Illuminating Firefly Diversity: Trends, Threats and Conservation Strategies

Fireflies are a diverse group of bioluminescent beetles belonging to the family Lampyridae. Recent research on their diversity, evolution, behavior and conservation has greatly advanced our scientific understanding of these charismatic insects. In this review, we first summarize new discoveries about their taxonomic and ecological diversity, then focus on recent endeavors to identify and protect threatened fireflies around the world. We outline the main threats linked to recent population declines (habitat loss and degradation, light pollution, pesticide overuse, climate change and tourism) and describe relevant risk factors that predict which species will be particularly vulnerable to these threats. Although global coordination of firefly conservation efforts has begun only recently, considerable progress has already been made. We describe work by the IUCN SSC Firefly Specialist Group to identify species currently facing elevated extinction risks and to devise conservation strategies to protect them. To date, IUCN Red List assessments have been completed for 150 firefly taxa, about 20% of which face heightened extinction risks. The conservation status for many species has yet to be determined due to insufficient information, although targeted surveys and community science projects have contributed valuable new data. Finally, we highlight some examples of successful firefly habitat protection and restoration efforts, and we use the framework of the IUCN SSC Species Conservation Cycle to point out high-priority actions for future firefly conservation efforts.

Biomarkers of oral subacute toxicity of deltamethrin in exposed male Albino rats

Deltamethrin is one of the most effective pyrethroid compounds, widely employed in veterinary medicine, public health, and farming. Deltamethrin-triggered oxidative stress largely causes serious harm to an organism. Acute toxicity of this compound was extensively investigated, while less information is available on its oral sub-acute effects. This study assessed, in the male Albino rats, the effects of oral gavage of either 0.874 mg/kg (0.01 LD50) or 8.740 mg/kg (0.10 LD50) of deltamethrin for successive 14 days to investigate its effects on biomarkers and to detect the tissue injury in rats following subacute deltamethrin treatment. It was found that levels of glutathione peroxidase, superoxide dismutase, and catalase in the brain, kidney, and liver, alkaline phosphatase (ALP), and uric acid in serum, hematocrit, mean corpuscular volume (MCV), white blood cells (WBC)s, eosinophils, and basophils were significantly reduced compared with untreated rats. However, when rats were treated with deltamethrin for successive 14 days, alanine aminotransferase (ALT) and lactate dehydrogenase (LDH) activities in serum and the levels of thiobarbituric acid reactive substances (TBARs) in brain, kidney, and liver, red blood cell distribution width (RDW-CV), total protein, monocytes, and basophils and the ratios of neutrophils to lymphocytes, an aggregated marker of systemic inflammation and systemic immune inflammation indexes, significantly increased compared with the control group. Histologic lesions were observed in the liver, kidney, brain, testis, and epidemies in rats exposed to subacute deltamethrin for 14 days, and most tissues of rats treated with 0.10 LD50 of deltamethrin were more affected than those treated with 0.01 LD50. These findings strongly suggest that subacute exposure to deltamethrin caused significant systemic toxicity through oxidative stress resulting in biochemical and histological changes in the studied tissues. These findings highlight the potential harmful effects of deltamethrin and emphasize the importance of understanding the subacute effects of this compound, particularly in the context of veterinary medicine, public health, and farming.

Microbiology and Biochemistry of Pesticides Biodegradation

Pesticides are chemicals used in agriculture, forestry, and, to some extent, public health. As effective as they can be, due to the limited biodegradability and toxicity of some of them, they can also have negative environmental and health impacts. Pesticide biodegradation is important because it can help mitigate the negative effects of pesticides. Many types of microorganisms, including bacteria, fungi, and algae, can degrade pesticides; microorganisms are able to bioremediate pesticides using diverse metabolic pathways where enzymatic degradation plays a crucial role in achieving chemical transformation of the pesticides. The growing concern about the environmental and health impacts of pesticides is pushing the industry of these products to develop more sustainable alternatives, such as high biodegradable chemicals. The degradative properties of microorganisms could be fully exploited using the advances in genetic engineering and biotechnology, paving the way for more effective bioremediation strategies, new technologies, and novel applications. The purpose of the current review is to discuss the microorganisms that have demonstrated their capacity to degrade pesticides and those categorized by the World Health Organization as important for the impact they may have on human health. A comprehensive list of microorganisms is presented, and some metabolic pathways and enzymes for pesticide degradation and the genetics behind this process are discussed. Due to the high number of microorganisms known to be capable of degrading pesticides and the low number of metabolic pathways that are fully described for this purpose, more research must be conducted in this field, and more enzymes and genes are yet to be discovered with the possibility of finding more efficient metabolic pathways for pesticide biodegradation.

Microbial detoxification of bifenthrin insecticide by selected fungal strains and optimizing conditions using response surface methodology for agricultural sustainability

Bifenthrin is a type I broad spectrum pyrethroid insecticide widely employed in urban and agricultural settings with little knowledge about its biodegradation. Bifenthrin was subjected to a 35 days incubation period in which it was degraded by five fungal strains named as Aspergillus niger, Aspergillus flavus, Aspergillus fumigatus, Penicillium chrysogenum, and Lasiodiplodia theobromae. Penicillium chrysogenum was found to be extremely effective in degrading bifenthrin up to 85%. Furthermore, response surface methodology (RSM) with Box-Behnken design is applied to optimize the degradation conditions with varying pH, temperature (°C), and incubation time (days). The p value < 0.05 in the response surface design and analysis of variance showed the significance of the reaction parameters. The ideal conditions for Penicillium chrysogenum to break down bifenthrin (10 mgL-1) were found to be 30 °C, pH 7, and a 24 days incubation period. In eutrophic conditions and a glucose-rich media, this fungus co-metabolized bifenthrin. By hydrolytically cleaving the carboxyl ester bond, the Penicillium chrysogenum breaks down bifenthrin, as shown by the chromatogram of four metabolites from GCMS. The biodegradation of bifenthrin by strain Penicillium chrysogenum and its use in agronomic situations are now well understood as per the findings of this study.

Influence of bifenthrin exposure at different gestational stages on the neural development

Perinatal exposure to bifenthrin (BF) alters neurodevelopment. However, the most susceptible time period to BF exposure and the possible mechanisms are not clear. In the current study, pregnant female mice were treated with BF (0.5 mg/kg/d) at three different stages [gestational day (GD) 0-5, 6-15 and 16-birth (B)] and neurologic deficits were evaluated in offspring mice. BF exposure at GD 16-B significantly altered the locomotor activity and caused learning and memory impairments in 6-week-old offspring. Gestational BF exposure also caused neuronal loss in the region of cornu ammonis of hippocampi of 6-week-old offspring. Interestingly, neurobehavioral impairments and neuronal loss were not observed in offspring at 10-week-old. BF exposure at GD 16-B also decreased protein levels of VGluT1, NR1 and NR2A while increased the protein levels of NR2B and VGAT1, as well as the gene levels of Il-1β, Il-6 and Tnf-α in hippocampi of 6-week-old offspring. Collectively, these data demonstrate that gestational exposure to a low dose BF causes neurodevelopmental deficits that remit with the age and the late-stage of pregnancy is the most susceptible time window to BF exposure. Imbalance in excitatory/inhibitory neuronal transmission, altered expression levels of NMDA receptors and increased neural inflammation may be associated with BF prenatal exposure-triggered neurobehavioral impairments.

Synthesis, and biological evaluation of pyrazole matrine derivatives as an insecticide against Spodoptera frugiperda

As one of the major threats to global food security, Spodoptera frugiperda (S. frugiperda) is highly gaining consideration due to its severe damage. Matrine is a widely and effectively used botanical insecticide in controlling S.frugiperda but lacks a rapidly available effect. To further improved the insecticidal activity of matrine based on combination principles, this work synthesized five new pyrazole matrine derivatives (PMDs) using Michael addition and investigated insecticidal activity against 2nd instar larvae of S. frugiperda(in vivo) and its isolated cell(in vitro). Our result demonstrated that PMDs show higher pesticidal activity than that matrine in both in vitro and in vivo assays. The most toxic derivatives in vitro and in vivo are PMD-3 and PMD-1, with IC50 of 2.49 mM and LC50 of 22.76 mg/L respectively. This research also investigates the anti-proliferation mechanism of PMDs based on isolated cells. PMDs decrease mitochondria membrane potential, arrested cell cycle at the G2/M phase, and upregulated Caspase 3, Caspase 9, and Apaf-1 to induce Caspase-dependent apoptosis. For Caspase-independent apoptosis, AIF and Endo G were found to be upregulated. Besides, pro-apoptotic factors like p53, IBM-1, and anti-apoptotic factors like IAP were upregulated. Moreover, we supposed that there was a linkage between lysosomes and PMD-induced apoptosis according to increased apoptosis rate, activated lysosomes, and upregulated Cathepsin B. This research provides new ideas for the synthesis of matrine derivatives and further demonstrated the anti-proliferation mechanism of PMDs.

Seasonal occurrence and risk assessment of endocrine-disrupting compounds in Tagus estuary biota (NE Atlantic Ocean coast)

Estuaries are continually threatened by anthropogenic pressures, consequently, a large group of contaminants harmful to human health affects the aquatic biota; therefore, it is necessary to monitor their quality. This study deals with the determination of a large group of compounds representing different endocrine-disrupting compounds (EDCs) classes [21 pesticides, 4 polycyclic musk fragrances, 4 UV-filters, 7 bisphenols, 6 polybrominated diphenyl ethers (PBDEs) and 8 of their methoxylated (MeO-BDEs)] in several estuarine species (fish, bivalves, crustaceans, earthworm, and macroalgae) collected seasonally along one year in two distinct areas of Tagus River estuary ("contaminated" vs. "clean" areas). The most abundant compounds found were galaxolide (HHCB) (81% positive samples; 0.04-74 ng/g ww), isoamyl 4-methoxycinnamate (IMC) (64%; 1.13-251 ng/g ww), alachlor (44%; 0.08-16 ng/g ww), and BDE-47 (36%; 0.06-2.26 ng/g ww). Polycyclic musks were the most frequent contaminants in fish (seabass, barbus, mullet, and sole) and macroalgae samples, while UV-filters were predominant in bivalves and crustaceans, and bisphenols in earthworms. Seasonal variation was verified for Σpesticides and Σmusks, with significantly higher levels in summer and autumn, whereas ΣUV-filters highest levels were found in spring and summer, and for ΣPBDEs statistically higher levels were registered in cold seasons (autumn and winter). Σbisphenols were significantly lower in spring than in the other seasons. In general, considering all species analysed in both areas, no statistically significant differences (p > 0.05) were verified between the two collection areas. Based on the estimated daily intake data, consumption of fish from this estuary is unlikely to be a human health concern, since the levels of contamination were below the toxicological threshold values. Overall, the data obtained in this study will allow regulatory authorities to identify and prioritize contaminants monitoring programs in estuaries, such as the case of bisphenol A, which was found, for the first time, in earthworm and clam species.

Organophosphate Pesticides and Pyrethroids in Farmland of the Pearl River Delta, China: Regional Residue, Distributions and Risks

A regional-scale survey was conducted to assess the occurrence, distribution, and risk of two extensively used pesticides (organophosphate pesticides and pyrethroids) in agricultural soils from the Pearl River Delta (PRD), South China. All target organophosphate pesticides (OPPs) and pyrethroids (PYs) were detected in the soil samples and both with a detection rate of 100%. The residues of the sum of six OPPs and the sum of four PYs were in the range of LOD-991 ng/g and 8.76-2810 ng/g, respectively. Dimethoate was the dominant OPPs, and fenpropathrin was the predominant PYs in the soils of the PRD region. With intensive agricultural activities, higher residues of OPPs and PYs in soils were detected closer to the seaside, among which Zhuhai city and Huizhou city suffered more serious combined pesticide pollution. The vertical compositional profiles showed that dimethoate could be detected through each soil layer in the PRD region's nine cities. The human exposure estimation of OPPs showed insignificant risks to the local population. In contrast, cypermethrin and fenpropathrin showed a potential ecological risk of 2.5% and 3.75% of the sampling sites, respectively. These results can facilitate those commonly used pesticide controls and promote sustainable soil management.

Androgen receptor signaling and pyrethroids: Potential male infertility consequences

Infertility is a global health concern inflicting a considerable burden on the global economy and a severe socio-psychological impact. Approximately 15% of couples suffer from infertility globally, with a male factor contribution of approximately 50%. However, male infertility remains largely unexplored, as the burden of infertility is mostly assigned to female people. Endocrine-disrupting chemicals (EDCs) have been proposed as one of the factors causing male infertility. Pyrethroids represent an important class of EDCs, and numerous studies have associated pyrethroid exposure with impaired male reproductive function and development. Therefore, the present study investigated the potentially toxic effects of two common pyrethroids, cypermethrin and deltamethrin, on androgen receptor (AR) signaling. The structural binding characterization of cypermethrin and deltamethrin against the AR ligand-binding pocket was performed using Schrodinger's induced fit docking (IFD) approach. Various parameters were estimated, such as binding interactions, binding energy, docking score, and IFD score. Furthermore, the AR native ligand, testosterone, was subjected to similar experiments against the AR ligand-binding pocket. The results revealed commonality in the amino acid-binding interactions and overlap in other structural parameters between the AR native ligand, testosterone, and the ligands, cypermethrin and deltamethrin. The estimated binding energy values of cypermethrin and deltamethrin were very high and close to those calculated for AR native ligand, testosterone. Taken together, the results of this study suggested potential disruption of AR signaling by cypermethrin and deltamethrin, which may result in androgen dysfunction and subsequent male infertility.

Atmospheric deposition of particulate matter from beef cattle feedlots is a likely contributor of pyrethroid occurrence in isolated wetland sediment: Source apportionment and ecological risk assessment

Industrial cattle feeding operations (feedlots) have been subject to public scrutiny in recent decades regarding environmental impacts of site runoff and aerial dispersion of agrochemical-laden particulate matter (PM). However, source apportionment of multi-use pesticides is challenging in mixed agricultural settings. Beef cattle on feed and row crop production are heavily concentrated in the Southern Great Plains of North America, where playa wetlands are vulnerable to agrochemical inputs and sedimentation from surrounding land use. In the current study, playa basin sediment (n = 33) was analyzed via UHPLC-MS for 21 agrochemicals spanning eight classes (macrocyclic lactones, neonicotinoids, organophosphates, pyrethroids, triazoles, β-methoxyacrylates, a carboximide, and phenylpyrazole). Pyrethroids were detected most frequently (75.8% of basins). Sediment pyrethroid concentrations were also significantly correlated (R² = 0.178, p = 0.007) with feedlot proximity (<1-50 km). Principal component analysis (PCA) of land use metrics extracted three principal components (74.3% of total variance), with principal component regression (PCR) showing the greatest agrochemical occurrence in basins heavily weighted by cropland buffer acreage (≤1 km) and feedlot proximity. Sediment toxicity benchmarks protective of two benthic invertebrates (Hyallela azteca and Chironomus spp.) identified λ-cyhalothrin, fenvalerate, and esfenvalerate as individual compounds exceeding levels of acute (RQ > 0.5) and chronic (RQ > 1) concern in >5% and >50% of cases, respectively. However, additive toxicity of co-occurring pyrethroids represents an acute high risk (RI > 1; median RI; acute = 2.4, chronic = 38.6) to benthic invertebrates in >75% of cases, which may threaten higher-order wetland taxa via bioaccumulation and trophic transfer.

Updating the Insecticide Resistance Status of Aedes aegypti and Aedes albopictus in Asia: A Systematic Review and Meta-Analysis

Background: Aedes aegypti and Aedes albopictus are two important vectors of several important arboviruses, including the dengue, chikungunya, and Zika viruses. Insecticide application is an important approach to reduce vector abundance during Aedes spp.-borne outbreaks in the absence of effective vaccines and treatments. However, insecticide overuse can result in the development of resistance, and careful monitoring of resistance markers is required. Methods: This meta-analysis and systematic review explored the spatial and temporal patterns of insecticide resistance in Asia from 2000 to 2021. PubMed, Scopus, EbscoHost, and Embase were used to enhance the search capability. The random-effects model was applied for the 94 studies that met our inclusion criteria for qualitative synthesis and meta-analysis. Results: Four major insecticides were studied (malathion, dichlorodiphenyltrichloroethane, permethrin, and deltamethrin). Dichlorodiphenyltrichloroethane resistance rates were high in both Ae. aegypti and Ae. albopictus (68% and 64%, respectively). Conversely, malathion resistance was less prevalent in Ae. aegypti (3%), and deltamethrin resistance was less common in Ae. albopictus (2%). Ae. aegypti displayed consistently high resistance rates (35%) throughout the study period, whereas the rate of insecticide resistance in Ae. albopictus increased from 5% to 12%. The rates of the major kdr mutations F1534C, V1016G, and S989P were 29%, 26%, and 22%, respectively. Conclusions: Insecticide resistance in both Ae. aegypti and Ae. albopictus is widespread in Asia, although the rates vary by country. Continuous monitoring of the resistance markers and modification of the control strategies will be important for preventing unexpected outbreaks. This systematic review and meta-analysis provided up-to-date information on insecticide resistance in dengue-endemic countries in Asia.

Impacts of Pesticides on Oral Cavity Health and Ecosystems: A Review

Pesticides are chemical substances used to control, prevent, or destroy agricultural, domestic, and livestock pests. These compounds produce adverse changes in health, and they have been associated with the development of multiple chronic diseases. This study aimed to present a detailed review of the effect of pesticides on the oral cavity and the oral microbiome. In the oral cavity, pesticides alter and/or modify tissues and the microbiome, thereby triggering imbalance in the ecosystem, generating an inflammatory response, and activating hydrolytic enzymes. In particular, the imbalance in the oral microbiome creates a dysbiosis that modifies the number, composition, and/or functions of the constituent microorganisms and the local response of the host. Pesticide exposure alters epithelial cells, and oral microbiota, and disrupts the homeostasis of the oral environment. The presence of pesticides in the oral cavity predisposes the appearance of pathologies such as caries, periodontal diseases, oral cancer, and odontogenic infections. In this study, we analyzed the effect of organochlorines, organophosphates, pyrethroids, carbamates, bipyridyls, and triazineson oral cavity health and ecosystems.

Complexation and enantioselectivity of novel bridge-like uranyl- 2-((1Z,9Z)-9-(2-Hydroxyphenyl)-3,5,6,8-tetrahydrobenzo[h][1,4,7,10] dioxadiazacyclododecin-2-yl)-5-methoxyphenol with chiral organophosphorus pesticide enantiomers of R/S-malathions

Designing new uranyl complexes with enantioselectivity is of great significance for the identification and separation of enantiomers of chiral pesticides. In this paper, a new asymmetric rigid uranyl-2-((1Z,9Z)-9-(2-Hydroxyphenyl)-3,5,6,8-tetrahydrobenzo[h][1,4,7,10] dioxadiaza-cyclododecin-2-yl)-5-methoxyphenol(Uranyl-HTDM) was designed, we used Uranyl-HTDM as a receptor to selectively coordinate with the guests of the chiral organophosphorus pesticide R/S-malathions(R/S-MLTs) to explore the receptor's enatioselectivity recognition of the chiral guests of R/S-MLTs. Density functional theory (DFT) method was used to comprehensively study the complexation mode of the receptor with enantiomers. The results showed that the U of Uranyl-HTDM could coordinate with both the thiophosphoryl sulfur and carbonyl oxygens of R/S-MLTs in different environments, respectively. The thermodynamics calculations further indicated that the receptor could selectively recognize the thiophosphoryl sulfur and carbonyl oxygen atoms of R/S-malathions, and the complexation abilities of Uranyl-HTDM to the R/S-malathions under different solvents were not the same. The smaller the polarity of solvents, the stronger the complexation ability of Uranyl-HTDM with R-malathion, toluene was an ideal solvent with large △G change and enatioselectivity coefficient of 99.55%. The study provides useful references for the design of new uranyl-salophens and for the experimental study on the molecular recognition of chiral organophosphorus pesticides.

Influence of perinatal deltamethrin exposure at distinct developmental stages on motor activity, learning and memory

BACKGROUND

Perinatal exposure to deltamethrin (DM) causes attention-deficit/ hyperactivity disorder-like behaviors. However, the vulnerable time window to DM exposure and the possible mechanism are obscure. We aimed to identify the critical window(s) at perinatal stages for DM exposure and the possible mechanism.

METHOD

Pregnant mice were exposed to DM (0.5 mg/kg) at three different prenatal stages [gestational day (GD) 0-5, 6-15 and 16-birth (16-B)] and early postnatal stage (PD 0-10). Locomotor activity, learning and memory were evaluated using open field and Y-maze test, respectively. Nissl staining and western blots were used to examine the neuronal loss and the protein expression, respectively.

RESULTS

Perinatal exposures to DM had no effect on reproductive and growth index of offspring. However, mice receiving DM exposure during GD 16-B displayed significantly higher mortality suggesting GD 16-B is the most vulnerable time window to DM exposure. Prenatal but not early postnatal DM exposure impaired locomotor activity, learning and memory, and caused neuron loss in the dentate gyrus of male offspring. However, neither prenatal nor postnatal DM exposure affected mouse behavior of female offspring. Prenatal DM exposures decreased the protein levels of NR2A and NR2B in both hippocampi and cerebral cortices of male offspring. However, female mice receiving DM exposure at GD 16-B but not other stages displayed increased expression levels of NR2A and NR2B in hippocampi.

CONCLUSION

Prenatal but not early postnatal DM exposure impairs the neuron development in male but not female mice. Altered NMDA receptor expression may correlate to DM-induced behavioral deficits.

A worldwide review of currently used pesticides' monitoring in agricultural soils

The adverse effects of pesticides on the agricultural ecosystem have been matter of concern in recent decades. However, attention has mostly been directed to highly persistent chemicals leading to underestimating currently used pesticides. In this review we present an overview of the studies on monitoring currently used pesticides in agricultural soils around the world published in the last 50 years. Furthermore, all data available in the articles has been integrated into one united data set. Finally, an overall meta-analysis on the prepared data set was performed. The result of the meta-analysis has been presented in this article. It was revealed that the occurrence of currently used pesticides in the soil of agricultural regions was alarming in many countries, establishing the need for long-term monitoring programs, especially in regions with intensive agricultural activities, in order to determine real-world currently used pesticides fate and accumulation in the soil.

Insecticide Resistance in Aedes aegypti Varies Seasonally and Geographically in Texas/Mexico Border Cities

Insecticide use is the primary method of attempting to reduce or control the spread of mosquito-borne diseases. Insecticide resistance is a major concern as resistance will limit the efficacy of vector-control efforts. The lower Rio Grande Valley region of South Texas has had autochthonous transmission of multiple mosquito-borne diseases including those caused by dengue virus, chikungunya virus, and Zika virus. However, the current status of mosquito resistance to commonly used pesticides in this region is unknown. In this study, we collected field samples from multiple municipalities in South Texas and assessed resistance using the Centers for Disease Control and Prevention bottle bioassay. All populations exhibited characteristics of resistance, and permethrin was the most effective insecticide with an average mortality rate of 44.78%. Deltamethrin and sumethrin had significantly lower mortality rates of 20.31% and 32.16%, respectively, although neither of these insecticides are commonly used for vector-control activities in this region. Depending on which insecticide was used, there was little significance between each of the 7 cities. Seasonal variation in resistance was observed among the collection sites. Both deltamethrin and sumethrin exhibited an increase in susceptibility over the course of 10 months, while permethrin exhibited a decrease in susceptibility. These data highlight the need for further studies to determine if variations in resistance observed are repeated. The data and future findings may be useful in determining the most effective strategies for pesticide use and rotation.

Andean Plants Essential Oils: A Scented Alternative to Synthetic Insecticides for the Control of Blowflies

Blowflies are vectors of microorganisms and human pathogens, and their maggots cause myiasis in vertebrates and infest and spoil meat and fish products. Essential oils (EOs) from spices were proven to be a safer and more sustainable alternative to synthetic insecticides for the control of blowflies and are suitable for protecting food from such pests. However, some EOs are not acceptable for environmental or topical applications due to their strong, unpleasant odour. In this study, we measured the acute toxicity and the repellence of two EOs extracted from the Andean plants Aloysia citrodora Palau and Bursera graveolens (Kunth) Triana and Planch., both known for their pleasant odour, against the blue blowfly Calliphora vomitoria (L.) (Diptera: Calliphoridae). We also compared their bioactivity with that of the Allium sativum L. EO, which is very effective but bad-smelling. The A. citrodora EO was mainly rich in oxygenated monoterpenes, the most abundant of which were geranial (26.8%) and neral (21.0%). The B. graveolens EO was chiefly composed of monoterpene hydrocarbons, mostly represented by limonene (46.2%). According to the sensory description, the best odour profile was associated with the A. citrodora EO, while the olfactory expression of the EO from B. graveolens was negatively affected by a strong odour of "mouldy lemon". The behavioural test showed that the A. citrodora EO was more repellent than that of A. sativum and, on the contrary, that the B. graveolens EO was attractive. The toxicity tests showed that the EOs of both Andean plants have a clear toxic effect on the C. vomitoria eggs and adults. In terms of ovicidal activity, there were no significant differences among the effects of the three tested EOs. On the adult flies, the toxicity of the two EOs of the Andean plants was much lower than that of A. sativum (LC₅₀ fumigation = 1.86 μL EO L^-1 air; LC₅₀ ingestion = 8.10 μL EO mL^-1 gel) both by fumigation (LC₅₀ = 23.66 and 25.30 μL EO L^-1 air for A. citrodora and B. graveolens, respectively) and ingestion (LC₅₀ = 36.65 and 44.97 μL EO mL^-1 gel for A. citrodora and B. graveolens, respectively), while, by contact, the A. citrodora EO (LD₅₀ = 0.27 μL EO insect^-1) was more toxic than the A. sativum EO (LD₅₀ = 0.46 μL EO insect^-1).

Toxicity and repellent activity of monoterpene enantiomers to rice weevils (Sitophilus oryzae)

BACKGROUND

The rice weevil, Sitophilus oryzae (L., 1763) (Coleoptera: Curculionidae), is a stored grain/seed pest of several crops. Botanicals represent an option to manage this pest, especially those with high toxicity determined by its structure and physicochemical properties and low residue left behind on treated grains/seeds. Enantiomers are bioactive molecules in organic processes. The aim of this study was to evaluate the insecticidal activity of two enantiomeric forms of the monoterpenes citronellal, limonene, linalool, menthone and α-pinene against S. oryzae adults through contact, fumigant and repellent assays.

RESULTS

All results were compared with absolute acetone as the negative control and those from contact assays also with malathion as the positive control. (S)-(-)-linalool was the most toxic by contact to S. oryzae and (S)-(-)-menthone through fumigation, while the two enantiomeric forms of menthone and α-pinene were the best repellents.

CONCLUSIONS

The high toxicity of only one of the two monoterpene enantiomers showed the importance of form and percentage of enantiomer in the commercial product, which affect the success of the product to controlling S. oryzae. © 2021 Society of Chemical Industry.

Dengue fever and insecticide resistance in Aedes mosquitoes in Southeast Asia: a review

Dengue fever is the most important mosquito-borne viral disease in Southeast Asia. Insecticides remain the most effective vector control approach for Aedes mosquitoes. Four main classes of insecticides are widely used for mosquito control: organochlorines, organophosphates, pyrethroids and carbamates. Here, we review the distribution of dengue fever from 2000 to 2020 and its associated mortality in Southeast Asian countries, and we gather evidence on the trend of insecticide resistance and its distribution in these countries since 2000, summarising the mechanisms involved. The prevalence of resistance to these insecticides is increasing in Southeast Asia, and the mechanisms of resistance are reported to be associated with target site mutations, metabolic detoxification, reduced penetration of insecticides via the mosquito cuticle and behavioural changes of mosquitoes. Continuous monitoring of the status of resistance and searching for alternative control measures will be critical for minimising any unpredicted outbreaks and improving public health. This review also provides improved insights into the specific use of insecticides for effective control of mosquitoes in these dengue endemic countries.

Metabolic profiles and non-targeted LC-MS/MS approach as a complementary tool to targeted analysis in assessment of plant exposure to pesticides

Liquid chromatography coupled with tandem mass spectrometry was employed for the detection of pesticides (thiamethoxam, lambda-cyhalothrin, deltamethrin, and metalaxyl) and their metabolites in Raphanus sativus var. longipinnatus exposed to these compounds under experimental conditions. Metalaxyl (0.008 mg/kg), metalaxyl acid (0.009 mg/kg), and (+)-trans-chrysanthemic acid (0.098 mg/kg) were identified in the plants exposed to the individual pesticides and their metabolites. Non-targeted analysis revealed the presence of thiamethoxam, lambda-cyhalothrin, and deltamethrin metabolites in plants exposed to these substances, despite the fact that the pesticide concentrations were below the analytical method's limit of quantification (0.005-0.006 mg/kg). Based on the non-targeted screening, non-specific (leucine and tyramine) and specific (epinephrine, dopamine, tryptamine, and serotonin) markers of plant exposure to the mentioned stress-inducing compounds were detected. These findings prove that non-targeted analysis is an indispensable tool for determining plants' exposure to pesticides, even when the parent compound has been completely metabolized.

Evaluation of the expression stability of reference genes in Apis mellifera under pyrethroid treatment

Honeybees (Apis mellifera L.), which unquestionably play an economically important role in pollination and agricultural production, are at risk of decline. To study changes in gene expression in insects upon exposure to pesticides or other external stimuli, appropriate reference genes are required for data normalization. Since there is no such gene that is absolutely invariable under all experimental conditions, the aim of this study was to identify the most stable targets suitable for subsequent normalization in quantitative experiments based on real-time polymerase chain reaction in honeybee research. Here, we evaluated the expression of fifteen candidate housekeeping genes from three breeding lines of honeybees treated with pyrethroids to identify the most stable genes. The tested insects were exposed to deltamethrin or lambda-cyhalothrin, and then, changes in the accumulation of selected transcripts were assessed, followed by statistical analyses. We concluded that AmRPL32, AmACT and AmRPL13a were the commonly recorded most stable genes in honeybees treated with the selected pyrethroids.

Exposure to Mosquito Repellents Causes Profound Development Defects and Induces Oxidative Stress in Zebrafish

Objective The study was designed to investigate the effects of commercially available mosquito repellents on embryonic development of zebrafish.

Materials and Methods Transfluthrin is a type I pyrethroid present in all commercial mosquito and insect repellents. Pyrethrins are neurotoxins that target the nervous system of insects. Three popular brands of liquid vaporizer repellents coded as compound A, B, and C that contained transfluthrin, ranging from 0.88 to 1.6% w/w, were used in this study. The effects of these compounds on the embryonic development of zebrafish were investigated. In addition, the ability of transfluthrin to induce oxidative stress was examined by analyzing the generation of reactive oxygen species in exposed embryos.

Results The exposure to mosquito repellents resulted in extensive morphological defects in zebrafish embryos. The severity of the anomalies correlated with the concentration of transfluthrin in the repellents. Exposure to pure transfluthrin generated high levels of reactive oxygen species in zebrafish embryos, suggesting the induction of oxidative stress.

Conclusion Liquid vaporizer repellents are generally used for control of mosquitos and are common in many households. This study demonstrated that its exposure to mosquito repellents causes severe morphological defects and embryonic lethality in zebrafish. The study also showed that transfluthrin, the active insecticide in these repellents, induces oxidative stress in zebrafish.

Esterase is a powerful tool for the biodegradation of pyrethroid insecticides

Agricultural and household applications of pyrethroid insecticides have significantly increased residual concentrations in living cells and environments. The enhanced concentration is toxic for living beings. Pyrethroid hydrolase enzyme (pyrethroid catalyzing esterase) regulates pyrethroid degradation, and has been well reported in various organisms (bacteria, fungi, insects and animals). Hydrolysis mechanisms of these esterases are different from others and properly function at factors viz., optimum temperature, pH and physicochemical environment. Active site of the enzyme contains common amino acids that play important role in pyrethroid catalysis. Immobilization technology emphasizes the development of better reusable efficiency of pyrethroid hydrolases to carry out large-scale applications for complete degradation of pyrethroids from the environments. In this review we have attempted to provide insights of pyrethroid-degrading esterases in different living systems along with complete mechanisms.

Contamination of pyrethroids and atrazine in greenhouse and open-field agricultural soils in China

A national-scale survey was conducted to assess the levels and distribution of two extensively used pesticides (pyrethroids and atrazine) in greenhouse and open-field soils in 20 provinces across China. Concentrations between 1.30 and 113 ng/g and 0.51-85.4 ng/g for the total pyrethroids (PYs) and of LOD-137 ng/g and LOD-134 ng/g for atrazine were found in greenhouse and open-field soils, respectively. Higher contaminations were found in the greenhouse than in the open fields. The levels of total pyrethroids in 80% of the greenhouses and of atrazine in 60% of the greenhouses were significantly higher than those in the nearby open-field soils (p < 0.05), respectively. The contamination of PYs and atrazine was generally more serious in the northern provinces of China, such as Heilongjiang, Jilin, Liaoning, Beijing, and Hebei. Pearson correlation analysis revealed that the contamination of PYs was significantly correlated with the soil total organic carbon (TOC) value in both greenhouse and open-field soils. Canonical correspondence analysis (CCA) showed that PYs might have an impact on the microbial alpha diversity, while cyhalothrin and cypermethrin may be the key factors affecting the microbial community in the greenhouse and open-field soils. The soil samples containing pesticide residues showed distinct taxonomic and functional communities, where an increased diversity and abundance of microorganisms able to degrade pesticides was observed with high-level PYs contamination. These findings provide useful information for evaluating PYs and atrazine pollution and for contamination management in greenhouse agriculture.

Insight Into Microbial Applications for the Biodegradation of Pyrethroid Insecticides

Pyrethroids are broad-spectrum insecticides and presence of chiral carbon differentiates among various forms of pyrethroids. Microbial approaches have emerged as a popular solution to counter pyrethroid toxicity to marine life and mammals. Bacterial and fungal strains can effectively degrade pyrethroids into non-toxic compounds. Different strains of bacteria and fungi such as Bacillus spp., Raoultella ornithinolytica, Psudomonas flourescens, Brevibacterium sp., Acinetobactor sp., Aspergillus sp., Candida sp., Trichoderma sp., and Candia spp., are used for the biodegradation of pyrethroids. Hydrolysis of ester bond by enzyme esterase/carboxyl esterase is the initial step in pyrethroid biodegradation. Esterase is found in bacteria, fungi, insect and mammalian liver microsome cells that indicates its hydrolysis ability in living cells. Biodegradation pattern and detected metabolites reveal microbial consumption of pyrethroids as carbon and nitrogen source. In this review, we aim to explore pyrethroid degrading strains, enzymes and metabolites produced by microbial strains. This review paper covers in-depth knowledge of pyrethroids and recommends possible solutions to minimize their environmental toxicity.

An Analytical Survey of Trace Heavy Elements in Insecticides

There are many types of insecticides traded in the local and international markets, which vary depending on the type of target insect (e.g., whether crawling or flying). This paper aimed to assess the concentration of trace elements present in the various pesticide formulations (solid, liquid, and gaseous). This study was conducted in two groups: the first group was comprised of zinc, copper, iron, chromium, phosphorus, selenium, and cobalt; the second group included four heavy toxic elements (arsenic, thallium, lead, and mercury). These elements were analyzed by inductively coupled plasma/optical emission spectrometry (ICP-OES).