The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform
Michael J Lydy - One of the best experts on this subject based on the ideXlab platform.
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Pyrethroid Insecticide Transport into Monterey Bay Through Riverine Suspended Solids
Archives of Environmental Contamination and Toxicology, 2012Co-Authors: Charlene M. Ng, Donald P. Weston, Michael J LydyAbstract:Pyrethroid pesticides are used widely in both agricultural and urban landscapes. Toxicity has been recorded in creeks and rivers throughout California, confirming that Pyrethroids move at least short distances from the areas of terrestrial application into downstream waterways. However, their further downstream transport into the marine ecosystem has received little study. The Monterey Bay was chosen as the study system in the current project due to the close proximity of both urban centers and intense agriculture. Suspended sediments were sampled from three major rivers during storm events and showed that Pyrethroids were routinely discharged from these coastal rivers, with concentrations of bifenthrin and permethrin in suspended solids of 22 and 83 ng/g, respectively. These suspended solids were deposited in estuaries and downstream reaches of rivers as they approached the coast where concentrations of Pyrethroids in the sediment were greater than those expected to be toxic. However, despite their transport onto the continental shelf, Pyrethroid residues were not detected in bed sediments of the shelf or in the nearby deep sea canyon, presumably due to dilution and degradation.
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joint toxicity of a Pyrethroid Insecticide cypermethrin and a heavy metal lead to the benthic invertebrate chironomus dilutus
Environmental Toxicology and Chemistry, 2011Co-Authors: Juan Du, Tyler W Mehler, Michael J LydyAbstract:Insecticides and heavy metals are frequently detected in the environment, but few studies have assessed the joint toxicity of organic and inorganic contaminants. Joint toxicity of a Pyrethroid Insecticide, cypermethrin, and a heavy metal, Pb2+, was evaluated in the present study. An antagonistic toxic response was observed when the benthic invertebrate Chironomus dilutus was simultaneously exposed to the two contaminants in both water and sediment exposures. Pre-exposure bioassays with midges were also conducted, and toxicity of cypermethrin was significantly reduced for midges that were pre-exposed to Pb2+. In addition, the impact of Pb2+ on the bioavailability of cypermethrin to midges was measured using Tenax extraction. No significant difference was noted in the amount of Tenax-extractable cypermethrin when different amounts of Pb2+ were added to sediment. Results suggested that altered organism sensitivity may contribute to the observed antagonistic interaction between cypermethrin and Pb2+, whereas the influence of changes in toxicokinetic processes such as uptake, biotransformation, and elimination on the joint toxicity should be further studied. Finally, the decreased toxicity of cypermethrin when simultaneously applied with Pb2+ may be one reason for the overestimation of sediment toxicity by cypermethrin alone in field-collected sediment. Environ. Toxicol. Chem. 2011;30:2838–2845. © 2011 SETAC
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identification and evaluation of Pyrethroid Insecticide mixtures in urban sediments
Environmental Toxicology and Chemistry, 2009Co-Authors: Andrew J Trimble, Donald P. Weston, Jason B Belden, Michael J LydyAbstract:Organochlorine, organophosphorous, and Pyrethroid Insecticides frequently have been detected together as mixtures in stream sediments. To simplify mixture analyses, additive toxic responses usually are assumed but rarely are confirmed, especially for compounds with similar modes of action. The first objective of the present study was to screen a database of 24 different pesticides and 94 urban-stream sediment samples collected throughout central and northern California (USA) to identify compounds and partial mixtures that dominated sample toxicity to Hyalella azteca. Pyrethroids and chlorpyrifos were the most toxicologically relevant compounds in terms of detection frequency, contribution to overall sample toxicity, and co-occurrence in the most common mixture patterns. Organochlorine Insecticides were the least toxicologically relevant compounds, with only a small percentage of samples exceeding predefined screening values. The second objective was to confirm that mixtures of type I and type II Pyrethroids display additive responses. Ten-day sediment toxicity tests of binary pesticide mixtures were conducted using H. azteca as the test organism. Observed dose-response curves were compared to those predicted from concentration-addition and independent-action models. Model deviation ratios (MDRs) were calculated at the median effect level to quantify the magnitudes of deviation between observed and predicted curves. Whereas the concentration-addition model adequately predicted toxicity for all the Pyrethroid mixtures (MDRs within a factor of two), dose-response values deviated from additivity enough to warrant further investigation.
Pat Sandra - One of the best experts on this subject based on the ideXlab platform.
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profiling the spatial concentration of allethrin and piperonyl butoxide using passive sorptive sampling and thermal desorption capillary gc ms
Chemosphere, 2008Co-Authors: Koen Desmet, Nathalie De Coensel, Tadeusz Gorecki, Pat SandraAbstract:Spatial concentration distribution of a chemical in an indoor environment is an important factor in the evaluation of chemical nuisances. However, straightforward techniques for the determination of this distribution are not very common and usually limited in their application. Sorptive sampling using polydimethylsiloxane-coated stir bars and the combination of active and diffusive sampling were shown to allow uncomplicated spatial concentration profiling of multiple compounds in an indoor environment. The validity of the approach was demonstrated in the analysis of the spatial concentration distribution of a Pyrethroid Insecticide in a common bedroom. The relative concentrations of allethrin and piperonyl butoxide were profiled throughout the room upon the application of an Insecticide vaporizer.
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short communication profiling the spatial concentration of allethrin and piperonyl butoxide using passive sorptive sampling and thermal desorption capillary gc ms
2008Co-Authors: Koen Desmet, Nathalie De Coensel, Pat SandraAbstract:Spatial concentration distribution of a chemical in an indoor environment is an important factor in the evaluation of chemical nuisances. However, straightforward techniques for the determination of this distribution are not very common and usually limited in their application. Sorptive sampling using polydimethylsiloxane-coated stir bars and the combination of active and diffusive sampling were shown to allow uncomplicated spatial concentration profiling of multiple compounds in an indoor environment. The validity of the approach was demonstrated in the analysis of the spatial concentration distribution of a Pyrethroid Insecticide in a common bedroom. The relative concentrations of allethrin and piperonyl butoxide were profiled throughout the room upon the application of an Insecticide vaporizer.
David M Soderlund - One of the best experts on this subject based on the ideXlab platform.
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resmethrin the first modern Pyrethroid Insecticide
Pest Management Science, 2015Co-Authors: David M SoderlundAbstract:The discovery of resmethrin almost five decades ago was the seminal event in the development of Pyrethroid Insecticides as important pest management tools, the value of which endures to this day. This brief review considers the development of Pyrethroids from the perspective of the discovery of resmethrin. I describe the pathway to the discovery of resmethrin and the unique properties that differentiated it from the pyrethrins and earlier synthetic Pyrethroids is described. I also summarize information on metabolic fate and mechanisms of selective toxicity, first elucidated with resmethrin, that have shaped our understanding of Pyrethroid toxicology since that time. Finally, I review the discovery pathway that led from resmethrin to the development of the first photostable, agriculturally useful Pyrethroids that established the importance of this Insecticide class. © 2014 Society of Chemical Industry
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Molecular mechanisms of Pyrethroid Insecticide neurotoxicity: recent advances
Archives of Toxicology, 2012Co-Authors: David M SoderlundAbstract:Synthetic Pyrethroid Insecticides were introduced into widespread use for the control of insect pests and disease vectors more than three decades ago. In addition to their value in controlling agricultural pests, Pyrethroids are at the forefront of efforts to combat malaria and other mosquito-borne diseases and are also common ingredients of household Insecticide and companion animal ectoparasite control products. The abundance and variety of Pyrethroid uses contribute to the risk of exposure and adverse effects in the general population. The insecticidal actions of Pyrethroids depend on their ability to bind to and disrupt voltage-gated sodium channels of insect nerves. Sodium channels are also important targets for the neurotoxic effects of Pyrethroids in mammals but other targets, particularly voltage-gated calcium and chloride channels, have been implicated as alternative or secondary sites of action for a subset of Pyrethroids. This review summarizes information published during the past decade on the action of Pyrethroids on voltage-gated sodium channels as well as on voltage-gated calcium and chloride channels and provides a critical re-evaluation of the role of these three targets in Pyrethroid neurotoxicity based on this information.
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human and rat nav1 3 voltage gated sodium channels differ in inactivation properties and sensitivity to the Pyrethroid Insecticide tefluthrin
Neurotoxicology, 2009Co-Authors: David M SoderlundAbstract:Abstract Voltage-gated sodium channels are important sites for the neurotoxic actions of Pyrethroid Insecticides in mammals. The pore-forming α subunits of mammalian sodium channels are encoded by a family of 9 genes, designated Nav1.1–Nav1.9. Native sodium channels in the adult central nervous system (CNS) are heterotrimeric complexes of one of these 9 α subunits and two auxiliary (β) subunits. Here we compare the functional properties and Pyrethroid sensitivity of the rat and human Nav1.3 isoforms, which are abundantly expressed in the developing CNS. Coexpression of the rat Nav1.3 and human Nav1.3 α subunits in combination with their conspecific β1 and β2 subunits in Xenopus laevis oocytes gave channels with markedly different inactivation properties and sensitivities to the Pyrethroid Insecticide tefluthrin. Rat Nav1.3 channels inactivated more slowly than human Nav1.3 channels during a depolarizing pulse. The rat and human channels also differed in their voltage dependence of steady-state inactivation. Exposure of rat and human Nav1.3 channels to 100 μM tefluthrin in the resting state produced populations of channels that activated, inactivated and deactivated more slowly than unmodified channels. For both rat and human channels, application of trains of depolarizing prepulses enhanced the extent of tefluthrin modification approximately twofold; this result implies that tefluthrin may bind to both the resting and open states of the channel. Modification of rat Nav1.3 channels by 100 μM tefluthrin was fourfold greater than that measured in parallel assays with human Nav1.3 channels. Human Nav1.3 channels were also less sensitive to tefluthrin than rat Nav1.2 channels, which are considered to be relatively insensitive to Pyrethroids. These data provide the first direct comparison of the functional and pharmacological properties of orthologous rat and human sodium channels and demonstrate that orthologous channels with a high degree of amino acid sequence conservation differ in both their functional properties and their sensitivities to Pyrethroid Insecticides.
Chao Xu - One of the best experts on this subject based on the ideXlab platform.
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enantioselectivity in aquatic toxicity of synthetic Pyrethroid Insecticide fenvalerate
Ecotoxicology and Environmental Safety, 2009Co-Authors: Linhua Chen, Xianting Lu, Chao XuAbstract:Abstract Synthetic Pyrethroids (SPs) are a family of chiral Insecticides with a large number of stereoisomers. Fenvalerate (FV) is one of the most potent Pyrethroid Insecticides, controlling a wide range of insect pests in agricultural fields, public health situations and animal houses. FV contains two chiral centers. In this study, four stereoisomers of FV were absolutely separated by high-performance liquid chromatography with a commercial chiral column, CHIRALCEL ® OJ-H, using n -hexane containing 1,2-dichloroethane and ethanol as mobile phase. Toxicity assays of each isomer and racemate of FV were performed using Daphnia magna ( D. magna ), zebrafish ( Danio rerio ) and zebrafish embryo-larval. In the acute toxicity of D. magna , significant differences were observed: the 24 h EC 50 of αS-2S -FV was 51 times more toxic than the αR-2R -FV, and the 48 h LC 50 results showed that the αS-2S -FV was 99 times more toxic than αR-2R -FV. In the toxicity assay of D. rerio , dramatic differences were also found: the LC 50 value of αS - 2S- FV was 17, 22, 39 and 56 times more toxic than the αR-2R -FV at 24, 48, 72 and 96 h, respectively. The assays of 4-day-old zebrafish embryo-larval showed that the exposure to FV enantioselectively induced crooked body, yolk sac edema and pericardial edema and that the αS-2S -FV was 3.8 times stronger than the other isomers in 96-h mortality. The results indicate that the enantiomeric differences should be taken into consideration in assessing the ecological effects of SPs.
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separation and aquatic toxicity of enantiomers of the Pyrethroid Insecticide lambda cyhalothrin
Environmental Toxicology and Chemistry, 2007Co-Authors: Chao Xu, Jiajia Wang, Daniel G Sheng, Yunjie TuAbstract:Chiral pollutants are receiving growing environmental concern due to differential biological activities of their enantio-mers. In the present study, enantiomeric separation of the Pyrethroid Insecticide lambda-cyhalothrin (LCT) was investigated by high-performance liquid chromatography (HPLC) using the columns of Chiralpak AD (amylase tris[3,5-dimethyl-phenylcarbamate]), Chiralpak AS (amylase tris[(S)-1-phenyl carbamate]), Chiralcel OD (cellulose tris[3,5-dimethylphenyl carbamate]), and Chiralcel OJ (cellulose tris[4-methyl benzoate]) with different chiral stationary phases. The differential toxicities of the enantiomers in aquatic systems were evaluated using the acute zebrafish (Danio rerio) toxicity test and the zebrafish embryo test. The enantiomers of LCT were separated completely on all the columns tested and detected by circular dichroism at 236 nm. Better separations were achieved at lower temperatures (e.g., 20°C) and lower levels of polar modifiers (≤5%) in mobile phase. Ethanol was found to be a good modifier of the mobile phase for all the columns, although isopropanol acted better for the Chiralcel OD column. The (—)-enantiomer was >162 times more toxic than its antipode to zebrafish in the acute test. The embryo test indicated that the exposure to LCT enantioselectively induced crooked body, yolk sac edema, and pericardial edema and that the (—)-enantiomer was 7.2 times stronger than the (+)-enantiomer in 96-h mortality. The malformations were induced by the racemate and its (—)-enantiomer at lower concentrations tested (e.g., 50 μg L−1), whereas the (+)-enantiomer induced malformations at relatively higher concentrations (≥100 μg L−1). These results suggest that the toxicological effects of chiral pesticides must be evaluated using their individual enantiomers.
Koen Desmet - One of the best experts on this subject based on the ideXlab platform.
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profiling the spatial concentration of allethrin and piperonyl butoxide using passive sorptive sampling and thermal desorption capillary gc ms
Chemosphere, 2008Co-Authors: Koen Desmet, Nathalie De Coensel, Tadeusz Gorecki, Pat SandraAbstract:Spatial concentration distribution of a chemical in an indoor environment is an important factor in the evaluation of chemical nuisances. However, straightforward techniques for the determination of this distribution are not very common and usually limited in their application. Sorptive sampling using polydimethylsiloxane-coated stir bars and the combination of active and diffusive sampling were shown to allow uncomplicated spatial concentration profiling of multiple compounds in an indoor environment. The validity of the approach was demonstrated in the analysis of the spatial concentration distribution of a Pyrethroid Insecticide in a common bedroom. The relative concentrations of allethrin and piperonyl butoxide were profiled throughout the room upon the application of an Insecticide vaporizer.
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short communication profiling the spatial concentration of allethrin and piperonyl butoxide using passive sorptive sampling and thermal desorption capillary gc ms
2008Co-Authors: Koen Desmet, Nathalie De Coensel, Pat SandraAbstract:Spatial concentration distribution of a chemical in an indoor environment is an important factor in the evaluation of chemical nuisances. However, straightforward techniques for the determination of this distribution are not very common and usually limited in their application. Sorptive sampling using polydimethylsiloxane-coated stir bars and the combination of active and diffusive sampling were shown to allow uncomplicated spatial concentration profiling of multiple compounds in an indoor environment. The validity of the approach was demonstrated in the analysis of the spatial concentration distribution of a Pyrethroid Insecticide in a common bedroom. The relative concentrations of allethrin and piperonyl butoxide were profiled throughout the room upon the application of an Insecticide vaporizer.
