Photodegradation of bifenthrin and deltamethrin-effect of copper amendment and solvent system

Overview of deltamethrin residues and toxic effects in the global environment

Pyrethroids are synthetic organic insecticides. Deltamethrin, as one of the pyrethroids, has high insecticidal activity against pests and parasites and is less toxic to mammals, and is widely used in cities and urban areas worldwide. After entering the natural environment, deltamethrin circulates between solid, liquid and gas phases and enters organisms through the food chain, posing significant health risks. Increasing evidence has shown that deltamethrin has varying degrees of toxicity to a variety of organisms. This review summarized worldwide studies of deltamethrin residues in different media and found that deltamethrin is widely detected in a range of environments (including soil, water, sediment, and air) and organisms. In addition, the metabolism of deltamethrin, including metabolites and enzymes, was discussed. This review shed the mechanism of toxicity of deltamethrin and its metabolites, including neurotoxicity, immunotoxicity, endocrine disruption toxicity, reproductive toxicity, hepatorenal toxicity. This review is aim to provide reference for the ecological security and human health risk assessment of deltamethrin.

Bifenthrin induces cell death in bovine mammary epithelial cells via ROS generation, calcium ion homeostasis disruption, and MAPK signaling cascade alteration

Bifenthrin is one of the widely used synthetic pyrethroid insecticides, employed for various purposes worldwide. As lipophilic pyrethroids can easily bind to soil particles, which is why their residues are detected in various environments. Consequently, the toxicity of bifenthrin to non-target organisms can be regarded as an environmental concern. The toxic effects of bifenthrin have been studied in various animal models and cell lines; however, its toxic effects on cattle remain unclear. In particular, gaining insights into the toxic effects of bifenthrin on the mammary lactation system is crucial for the dairy industry. Therefore, we proceeded to investigate the toxic effects of bifenthrin on the bovine mammary epithelial cells (MAC-T cells). We established that bifenthrin inhibited cell proliferation and triggered apoptosis in MAC-T cells. Additionally, bifenthrin induced mitochondrial dysfunction and altered inflammatory gene expression by disrupting mitochondrial membrane potential (MMP) and generating excessive reactive oxygen species (ROS). We also demonstrated that bifenthrin disrupted both cytosolic and mitochondrial calcium ion homeostasis. Furthermore, bifenthrin altered mitogen-activated protein kinase (MAPK) signaling cascades and downregulated casein-related genes. Collectively, we confirmed the multiple toxic effects of bifenthrin on MAC-T cells, which could potentially reduce milk yield and quality.

Green photosensitisers for the degradation of selected pesticides of high risk in most susceptible food: A safer approach

Pesticides are the leading defence against pests, but their unsafe use reciprocates the pesticide residues in highly susceptible food and is becoming a serious risk for human health. In this study, mint extract and riboflavin were tested as photosensitisers in combination with light irradiation of different frequencies, employed for various time intervals to improve the photo-degradation of deltamethrin (DM) and lambda cyhalothrin (λ-CHT) in cauliflower. Different source of light was studied, either in ultraviolet range (UV-C, 254 nm or UV-A, 320-380 nm) or sunlight simulator (> 380-800 nm). The degradation of the pesticides varied depending on the type of photosensitiser and light source. Photo-degradation of the DM and λ-CHT was enhanced by applying the mint extracts and riboflavin and a more significant degradation was achieved with UV-C than with either UV-A or sunlight, reaching a maximum decrement of the concentration by 67-76%. The light treatments did not significantly affect the in-vitro antioxidant activity of the natural antioxidants in cauliflower. A calculated dietary risk assessment revealed that obvious dietary health hazards of DM and λ-CHT pesticides when sprayed on cauliflower for pest control. The use of green chemical photosensitisers (mint extract and riboflavin) in combination with UV light irradiation represents a novel, sustainable, and safe approach to pesticide reduction in produce.

New Insights into the Degradation Path of Deltamethrin

Pyrethroids are among the insecticidal compounds indicated by the World Health Organization for mitigation of vector-borne diseases. Active deltamethrin (with chiral configuration α-S,1-R-cis) is one of the most effective pyrethroids characterized by low toxicity to humans, and it is currently tested as active ingredient for insecticidal paints. Nevertheless, several degradation processes can occur and affect the insecticidal efficacy in the complex paint matrix. In the present study, a detailed NMR analysis of deltamethrin stability has been carried out under stress conditions, mimicking a water-based insecticidal paint environment. Two novel by-products, having a diastereomeric relationship, were identified and their structure was elucidated by combining NMR, HPLC, GC-MS, and ESI-MS analyses. These compounds are the result from a nucleophilic addition involving deltamethrin and one of its major degradation products, 3-phenoxybenzaldehyde. Given the known toxicity of the aldehyde, this reaction could represent a way to reduce its concentration into the matrix. On the other hand, the toxicology of these compounds towards humans should be addressed, as their presence may adversely affect the performance of deltamethrin-containing products.

Bifenthrin in the tropical sugarcane ecosystem: persistence and environmental risk assessment

Termites are one of the major pests of sugarcane. Bifenthrin has label claim for use against sugarcane termites and is applied at the time of planting over the cane setts in the furrows. A thorough knowledge on the dissipation kinetics of bifenthrin in the soil and cane setts provides an insight into its dynamic behavior in the soil-plant-environment continuum, and hence, was studied in detail. The recoveries of the method adopted to determine the residues of bifenthrin in the soil, sugarcane setts, stem, and leaf were in the range of 92.78-98.19% at three levels of fortification ranged between 0.01 and 0.1 μg/g of matrix. At the recommended dose (100 g a.i./ha), bifenthrin was found to persist in the soil and cane setts up to 60 and 75 days after treatment (DAT) with the half-lives of 16.4 and 25.0 days, respectively. The dissipation kinetics of bifenthrin followed the biphasic model. At double the recommended dose, the residues persisted up to 75 DAT and reached below the detectable limit (< 0.01 μg/g) on 90 DAT both in the soil and setts. The half-life of bifenthrin was 22.0 days in the sandy clay loam soil and 17.6 days in/on the sugarcane setts. In the present study, dissipation by photolysis has been ruled out, as the treated setts were not exposed to sunlight. This could be one of the reasons for longer persistence of bifenthrin in the sugarcane setts up to 75 DAT with the half-life of more than 2 weeks. The bifenthrin residues were not detected in the leaf and stem of sugarcane plant throughout the experimental period. There could be harmful effects to earthworms (risk quotient > 1.0) due to the presence of bifenthrin residues in the soil of tropical sugarcane ecosystem.

Photodegradation kinetics, mechanism and aquatic toxicity of deltamethrin, permethrin and dihaloacetylated heterocyclic pyrethroids

Photochemical methods attracted much research interests for their high-efficiency and low secondary pollution. Decomposition of synthetic pyrethroids, the fourth major group of insecticides in use worldwide, was also of great significance due to their possible environmental risks. The photodegradation of deltamethrin, permethrin and dihaloacetylated heterocyclic pyrethroids in methanol/acetone = 9/1 (by volume) by a 400 W mercury lamp was examined. The t_1/2 of tested pyrethroids was less than 25 min, except for cis-permethrin with a t_1/2 of up to 50 min. The trans-isomer of permethrin and compound DCA-01 with a smaller t_1/2 might be more susceptible to degradation than their cis-isomer. Besides, the photodegradation of pyrethroids was divided into twelve pathways including isomerization, ester hydrolysis, ester bond cleavage, CO bond cleavage, 3,3-dimethylacrylate formation, double bond break, C1-C3 bond cleavage in cyclopropyl, reductive dehalogenation, decarboxylation, nucleophilic reagents attack on lone pair electrons on oxygen atoms in the phenyl ether, cyano hydrolysis, and halogenated hydrocarbon hydrolysis. The ECOSAR program displayed that pyrethroids and most of their photodegradation products were toxic to fish, daphnid, green algae. Particularly, some photodegradation products were more harmful to aquatic organisms than their parents.

Synthesis, insecticidal activity, resistance, photodegradation and toxicity of pyrethroids (A review)

Pyrethroids are a class of highly effective, broad-spectrum, less toxic, biodegradable synthetic pesticides. However, despite the extremely wide application of pyrethroids, there are many problems, such as insecticide resistance, lethal/sub-lethal toxicity to mammals, aquatic organisms or other beneficial organisms. The objectives of this review were to cover the main structures, synthesis, steroisomers, mechanisms of action, anti-mosquito activities, resistance, photodegradation and toxicities of pyrethroids. That was to provide a reference for synthesizing or screening novel pyrethroids with low insecticide resistance and low toxicity to beneficial organisms, evaluating the environmental pollution of pyrethroids and its metabolites. Besides, pyrethroids are mainly used for the control of vectors such as insects, and the non-target organisms are mammals, aquatic organisms etc. While maintaining the insecticidal activity is important, its toxic effects on non-target organisms should be also considered. Pyrethroid resistance is present not only in insect mosquitoes but also in environmental microorganisms, which results in anti-pyrethroids resistance (APR) strains. Besides, photodegradation product dibenzofurans is harmful to mammals and environment. Additionally, pyrethroid metabolites may have higher hormonal interference than the parents. Particularly, delivery of pyrethroids in nanoform can reduce the discharge of more toxic substances (such as organic solvents, etc.) to the environment.

Changes of various insecticides during in vitro human digestion

This study was performed to determine the effects of in vitro human digestion on the concentrations of five insecticides, namely 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT), 1,1-dichloro-2,2-bis(p-chlorophenyl)ethane (DDD), 2,2-bis(p-chlorophenyl)-1,1-dichloroethylene (DDE), bifenthrin, and fipronil. In vitro models included all the steps of human digestion, i.e., passage through the mouth, stomach, small intestine, and large intestine (with enteric bacteria). The concentrations of DDT and fipronil did not change (P > 0.05) until small intestinal digestion, whereas those of DDD, DDE, and bifenthrin decreased (P < 0.05) at each digestion step. The concentrations of all the insecticides decreased (P < 0.05) during the large intestinal digestion step with enteric bacteria, Lactobacillus sakei and Escherichia coli. In conclusion, the concentrations of all the tested insecticides decreased during all the steps of in vitro human digestion and were especially reduced by enteric bacteria during the large intestinal digestion step.