Residue dynamics and dietary risk assessment of new formulation of novaluron and lambda cyhalothrin on tomato.

Presence of residues on food commodities is major bottleneck of insecticide use under good agricultural practices (GAPs). The use of less persistent with two different mode of action insecticide is novel approach of getting maximum insect control without developing insecticide resistance. Novaluron, an insect growth disruptor and lambda cyhalothrin, a nerve poison has been used widely for the management of lepidopteran pests. Dissipation and consumer risk analysis studies were carried out on a new combination product of novaluron and lambda cyhalothrin are used for control insects of tomato at recommended standard dose of 71 + 14 g/ha and double dose of 142 + 28 g/ha of active ingredients. Extraction and cleanup of sample residues was done using QuEChERS technique and analyzed in GC-ECD. The residues of novaluron were dissipated within 10 to 15 days, and the residues of lambda cyhalothrin were at 7 to 10 days, both at the standard and double the standard dose, following a first order reaction kinetics. Analysis of risk and hazard quotient revealed that the test insecticides do not pose any dietary risk to consumer as TMDI < MPI and HQ < 1.

Pyrethroid residues in Indonesian river Citarum: A simple analytical method applied for an ecological and human health risk assessment.

Pyrethroid residues in the Citarum River, Indonesia, was first investigated based on their occurrences, water assimilative capacity, and risk assessment. In this paper, first, a relatively simple and efficient method was built and validated for analysis of seven pyrethroids in a river water matrix: bifenthrin, fenpropathrin, permethrin, ß-cyfluthrin, cypermethrin, fenvalerate, and deltamethrin. Next, the validated method was used to analyze pyrethroids in the Citarum River. Three pyrethroids, ß-cyfluthrin, cypermethrin, and deltamethrin, were detected in some sampling points with concentration up to 0.01 mg/L. Water assimilative capacity evaluation shows that ß-cyfluthrin and deltamethrin pollution exceed the Citarum river water capacity. However, due to hydrophobicity properties of pyrethroids, removal through binding to sediments are expected. Ecotoxicity risk assessment shows that ß-cyfluthrin, cypermethrin and deltamethrin pose risks to the aquatic organisms in the Citarum River and its tributaries through bioaccumulation in food chain. Based on bioconcentration factors of the detected pyrethroids, ß-cyfluthrin poses the highest adverse effect to humans while cypermethrin is the safest. Human risk assessment based on hazard index suggests that acute non-carcinogenic risk associated to consuming fish from the study location polluted with ß-cyfluthrin, cypermethrin and deltamethrin is unlikely. However, hazard quotient shows that chronic non-carcinogenic risk associated to consuming fish from the study location polluted with ß-cyfluthrin is likely. However, since the risk assessment was performed separately for each pyrethroid, further assessment on the impact of mixture pyrethroid to aquatic organisms and humans should be performed to explore the real impact of pyrethroids to the river system.

Sand as a solid support in ultrasound-assisted MSPD: A simple, green and low-cost method for multiresidue pesticide determination in fruits and vegetables.

Sand was studied as a solid support in ultrasound-assisted matrix solid-phase dispersion (UA-MSPD) for the extraction of different pesticide classes, including organophosphates, carbamates, triazoles and pyrethroids from fruits and vegetables, with determination by GC-MS and LC-MS/MS. The performance of sand was compared with that of different types of classic solid supports and alternative natural materials from renewable sources. The best results were obtained using 0.5 g sample, 1 g sand as a solid support, 20 mg activated charcoal and 5 mL ethyl acetate as elution solvent. Recoveries ranged from 55 to 140% with an RSD ≤ 20%. LOQs varied from 0.005 to 0.5 mg kg-1 for all analytes. Thiamethoxam, captan, chlorpyrifos, dimethoate and pyrimethanil were found in strawberry samples at concentrations from 0.01 to 0.06 mg kg-1. Acephate and tebuconazole were found in a tomato sample at concentrations of 0.45 and 0.30 mg kg-1, respectively. The method developed was efficient, simple, cheap, robust, and environmentally friendly.

Toxicological assessment of lambda-cyhalothrin and acetamiprid insecticides formulated mixture on hatchability rate, histological aspects, and protein electrophoretic pattern of Biomphalaria alexandrina (Ehrenberg, 1831) snails.

Several formulated mixtures of pesticides are widely used in modern agriculture. Nevertheless, the agriculture runoff causes a serious damage to the aquatic ecosystem. Therefore, the present study aims to use B. alexandrina snails as bioindicators for 30 g/l lambda-cyhalothrin and 17 g/l acetamiprid as a formulated mixture insecticide. Results showed that it has a molluscicidal activity against snails at LC50 7.9 mg/l. The hatchability percent of both treated 1-day-aged and/or 3-day-aged groups were less than that of the control group. The sublethal concentrations of the tested insecticide caused a remarkable abnormal necrosis in male and female gametogenic cells, besides a severe damage in both secretory and digestive cells. The results of SDS-PAGE protein profiles of treated snails showed that the least number of protein bands was noticed in snail groups that subjected to LC10 (6.6 mg/l) and LC25 (7.2 mg/l) concentrations when compared to control protein fractions.

Assessment of ethylene glycol diacetate as an alternative carrier for use in agrochemical emulsifiable concentrate formulation.

The conventional emulsifiable concentrate (EC) formulation contains a large amount of aromatic solvents, which causes adverse effects to both the environment and human health due to the toxicity of the solvents. Here, we developed a 2.5% lambda-cyhalothrin EC formulation with ethylene glycol diacetate (EGDA) as the solvent, and the developed formulation serves as an environmental-friendly alternative to overcome the adverse effects of aromatic solvents. The physicochemical characterizations, wettability properties, phytotoxicity and bioassays of the EGDA-EC formulation were systematically investigated and compared with that of the EC formulation with xylene as the solvent. The results showed that both EC formulations had excellent emulsion properties and storage stabilities. Additionally, the EGDA-EC formulation possessed a higher flash point (96 °C), indicating safer production, storage and transport. The retentions of the EGDA-EC sample on leaves were 1.22-1.46-fold higher than that of the xylene-EC sample, and the EGDA-EC also exhibited lower surface tensions and contact angles, which would benefit decreasing drift-off and improving utilization. Furthermore, the bioassays demonstrated that the EGDA-EC formulation had lower acute toxicity to aquatic organisms and higher control efficacy to target insects compared with the xylene-EC formulation. Therefore, EGDA is a promising carrier for oil-soluble agrochemicals to improve their application performance and reduce their adverse effects.

Dissipation kinetics and risk assessment of chlorfenapyr on tomato and cabbage.

A field experiment was conducted over two seasons to evaluate the dissipation kinetics and assess the risks of chlorfenapyr in tomato and cabbage following foliar application of chlorfenapyr 10% SC at 100 and 200 g a.i. ha-1. Samples of tomato, cabbage, and soil were analyzed and quantified by gas chromatography-electron capture detector (GC-ECD). The limit of detection (LOD) and limit of quantification (LOQ) of chlorfenapyr were found to be 0.01 and 0.03 mg kg-1, respectively, in tomato, cabbage, and soil. The dissipation of chlorfenapyr followed first-order kinetics. The compound showed less persistence in both the vegetables and soil as the calculated half-life values of chlorfenapyr ranged between 4.54 and 7.74 days considering two different doses and seasons. The residue was below detection limit in all the untreated plant and soil samples. The pre-harvest interval (PHI) of chlorfenapyr in both the vegetables was determined to be 9-14 days regardless of dose or season. The theoretical maximum residue contribution (TMRC) of chlorfenapyr was calculated for tomato and cabbage and was found to be lower than the maximum permissible intake (MPI) of the compound. Therefore, the application of chlorfenapyr at the recommended dose in tomato and cabbage for crop protection seems to be safe from both environmental contamination and consumer safety standpoints.

Computational Structural Pharmacology and Toxicology of Voltage-Gated Sodium Channels.

Voltage-gated sodium channels are targets for many toxins and medically important drugs. Despite decades of intensive studies in industry and academia, atomic mechanisms of action are still not completely understood. The major cause is a lack of high-resolution structures of eukaryotic channels and their complexes with ligands. In these circumstances a useful approach is homology modeling that employs as templates X-ray structures of potassium channels and prokaryotic sodium channels. On one hand, due to inherent limitations of this approach, results should be treated with caution. In particular, models should be tested against relevant experimental data. On the other hand, docking of drugs and toxins in homology models provides a unique possibility to integrate diverse experimental data provided by mutational analysis, electrophysiology, and studies of structure-activity relations. Here we describe how homology modeling advanced our understanding of mechanisms of several classes of ligands. These include tetrodotoxins and mu-conotoxins that block the outer pore, local anesthetics that block of the inner pore, batrachotoxin that binds in the inner pore but, paradoxically, activates the channel, pyrethroid insecticides that activate the channel by binding at lipid-exposed repeat interfaces, and scorpion alpha and beta-toxins, which bind between the pore and voltage-sensing domains and modify the channel gating. We emphasize importance of experimental data for elaborating the models.

Production of Insecticide Degradates in Juices: Implications for Risk Assessment.

This study was designed to observe the production of degradates of two organophosphorus insecticides and one pyrethroid insecticide in beverages. Purified water, white grape juice, apple juice, and red grape juice were fortified with 500 ng/g malathion, chlorpyrifos, and permethrin, and aliquots were extracted for malathion dicarboxylic acid (MDA), 3,5,6-trichloro-2-pyridinol (TCPy), and 3-phenoxybenzoic acid (3-PBA) several times over a 15 day period of being stored in the dark at 2.5 °C. Overall, first-order kinetics were observed for production of MDA, and statistically significant production of TCPy was also observed. Statistically significant production of 3-phenoxybenzoic acid was not observed. Results indicate that insecticides degrade in food and beverages, and this degradation may lead to preexisting insecticide metabolites in the beverages. Therefore, it is suggested that caution should be exercised when using urinary insecticide metabolites to assess exposure and risk.

Measurement of pyrethroids and their environmental degradation products in fresh fruits and vegetables using a modification of the quick easy cheap effective rugged safe (QuEChERS) method.

Pyrethroid insecticides are used extensively in agriculture, and they, as well as their environmental degradates, may remain as residues on foods such as fruits and vegetables. Since pyrethroid degradates can be identical to the urinary markers used in human biomonitoring, it is important to understand the contribution of these degradates when studying sources of human pyrethroid exposure. We modified the widely used Quick Easy Cheap Effective Rugged Safe (QuEChERS) method to measure several current-use pyrethroids (cis/trans-permethrin, cypermethrin, deltamethrin, esfenvalerate, bifenthrin, cyfluthrin, and cyhalothrin) and their environmental degradation products (3-PBA, cis/trans-DCCA, 4-F-3-PBA, DBCA, and MPA) in selected fresh fruits and vegetables. Using fortified samples, we determined extraction efficiencies from: tomatoes, oranges (whole, peeled, and rind), grapes, apples, bananas (peeled and rind only), onions, lettuce, green peppers, carrots and broccoli. For a subset of these food items (apples, grapes, tomatoes, lettuce and banana peel), we also established limits of detection (MDLs) and quantitation (MQLs). Each sample was homogenized (1kg) then spiked with the target pyrethroids and their degradation products. Sub-samples (15g) were extracted with acetonitrile, then salted out and partitioned with NaCl and MgSO4. The extract was divided and further cleaned using solid phase extraction (SPE) cartridges containing either graphitized non-porous carbon (pyrethroids) or C18 (degradation products). Sample analysis was via liquid chromatography/tandem mass spectrometry (LC-MS/MS). Considering the mean recoveries each of the 14 analytes in all 13 matrices: 42% of the recoveries were ≥90%, 70% were ≥80%, and 90% were ≥70%. All MDL's were less than 100ng/kg, except 3-PBA (132ng/kg, tomato), MPA (129ng/kg, tomato), and trans-permethrin (141ng/kg, banana peel). We then applied the method to non-spiked samples (subset of 5 for which the MDLs/MQLs had been determined) collected weekly for four weeks from local supermarkets. At least one pyrethroid was present in measureable concentrations in all matrices except banana peels. In contrast, the only degradation products detected were cis/trans-DCCA, in one lettuce sample.

Assessment of toxic interactions between deltamethrin and copper on the fertility and developmental events in the Mediterranean sea urchin, Paracentrotus lividus.

Deltamethrin pesticide and copper have intensively been used in agriculture and industrial activities and can finally reach the marine ecosystem at high concentrations affecting the health of organisms. In this study, we assessed under laboratory conditions the toxic interactions between deltamethrin and copper and their effects on the fertility rate, cell mitotic division rate, and embryo developmental events of the sea urchin (Paracentrotus lividus). The exposure of sperm to increasing concentrations of deltamethrin (6.10(-5) and 6.10(-2) µg/L) and copper (50 and 100 µg/L) or to their mixture (6.10(-5) µg/L of deltamethrin and 50 µg/L of CuSO4) caused a significant alteration on the fertilizing capability of spermatozoids. Concentration-dependent toxic effects on the early cleavage in P. lividus were observed in groups treated with copper, deltamethrin, and their mixture. The kinetics of early divisions was accelerated and the average size of pluteus larvae was decreased under pollutant treatments. Several developmental anomalies were identified in pluteus, including crossed skeletal tips at the hood apex, joined or atrophied arms, and alteration of general larva shape. In conclusion, the sea urchin represents a suitable and sensitive model for testing the toxicity and the effects of deltamethrin pesticide and copper in sea water. In addition, the sensitivity of various end points to studied contaminants, proved their utility in the infield biomonitoring studies.

Fast determination of pyrethroid pesticides in tobacco by GC-MS-SIM coupled with modified QuEChERS sample preparation procedure.

An analytical method was developed for the extraction and determination of pyrethroid pesticide residues in tobacco. The modified QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) method was applied for preparing samples. In this study, methyl cyanide (MeCN)-saturated salt aqueous was used as the two-phase extraction solvent for the first time, and a vortex shaker was used for the simultaneous shaking and concentration of the analytes. The effects of experimental parameters on extraction and clean-up efficiency were investigated and optimized. The analytes were determined by gas chromatography-mass spectrometry-selected ion monitoring (GC-MS-SIM). The obtained recoveries of the analytes at three different fortification levels were 76.85-114.1% and relative standard deviations (RSDs) were lower than 15.7%. The limits of quantification (LOQs) were from 1.28 to 26.6 µg kg(-1). This method was also applied to the analysis of actual commercial tobacco products and the analytical results were satisfactory.

Health risk assessment of pesticides residue in maize and cowpea from Ejura, Ghana.

Low productivity in agriculture due to damage cause by pests has led to the application of pesticides to control pest infestation. Residues of pesticides applied on crops are often found in the food which can cause chronic effect on the health of humans who consume such products. The aim of this study is to measure pesticides residues in maize and cowpea and compare the values with stablished safety limits. A total of 37 pesticides comprising 15 organochlorines, 13 organophosphorus and 9 pyrethroids pesticides were identified in maize and cowpea samples obtained from farms in Ejura. Analytical methods included solvent extraction of the pesticide residues and their subsequent quantification using gas chromatograph equipped with Electron Capture Detector and Pulse Flame Photometric Detector after clean-up on alumina/activated charcoal column. The results showed that the mean concentration of pesticides in maize ranged from 0.001 to 0.103 mg kg(-1) for organochlorine pesticides, 0.002-0.019 mg kg(-1) for organophosphorus pesticides and 0.002-0.028 mg kg(-1) for pyrethroids pesticides. In cowpea the mean concentration ranged from 0.001 to 0.108 mg kg(-1) for organochlorine pesticides, 0.002-0.015 mg kg(-1) for organophosphorus pesticides and 0.001-0.039 mg kg(-1) for pyrethroids pesticides. Maximum Residue Limits for ß-HCH, ß-endosulfan, p,p'-DDE and p,p'-DDD were exceeded in both maize and cowpea samples. Health risk estimation revealed that residues of heptachlor, dieldrin, endrin, ß-endosulfna, γ-chlordane and chlorfenvinphos found in maize exceeded the Acceptable Daily Intake. Similarly the levels of heptachlor and p,p'-DDD found in cowpea also exceeded the Acceptable Daily Intake. This suggests a great potential for chronic toxicity to consumers of these food items.

Dissipation kinetics and assessment of processing factor for chlorpyrifos and lambda-cyhalothrin in cardamom.

The dissipation kinetics and method for estimation of residues of chlorpyrifos and lambda-cyhalothrin in cardamom were studied and developed. The limit of detection and limit of quantitation arrived for the compounds were 0.01 and 0.025 µg g(-1), respectively. Gas chromatographic response of chlorpyrifos and lambda-cyhalothrin residues was linear in the range of 0.01-0.50 µg g(-1) and the mean recovery obtained was 97.3 % for chlorpyrifos and 98.9 % for lambda-cyhalothrin with satisfactory relative standard deviation values. The mean initial residues of chlorpyrifos applied at a concentration of 0.05 % in cardamom was 2.5 µg g(-1) and the residue was 8.1 µg g(-1) after processing, with a processing factor of 3.24, while lambda-cyhalothrin when applied at 0.0025 % resulted in initial residues of 1.63 µg g(-1) that magnified to 4.86 µg g(-1) on curing, with a processing factor of 2.98. The half-life of chlorpyrifos was in the range of 5.1-5.24 days while that of lambda-cyhalothrin was in the range of 4.40-4.55 days. The processing factor arrived at in the above experiment lead to the conclusion that the residues of chlorpyrifos got magnified to 3.24-3.68 times and that of lambda-cyhalothrin got magnified to 2.98-3.46 times of initial residues, consequent to loss of weight due to dehydration during curing.

Oxidative stress, biochemical and histopathological alterations in the liver and kidney of female rats exposed to low doses of deltamethrin (DM): a molecular assessment.

OBJECTIVE: To evaluate histopathological alterations of the liver and kidney of female rats exposed to low doses of DM and its potential genotoxic activity. METHODS: Female Wistar rats were randomly assigned to control (3 groups, 6 rats in each) and treatment groups (3 groups, 6 rats in each). They were subjected to subcutaneous injections of DM (at doses of 0.003, 0.03, and 0.3 mg/kg bw/d) after 30, 45, and 60 d, respectively. RESULTS: Significant alterations were recorded in liver parenchyma induced by hepatic vacuolization, fragmented chromatin in nuclei, dilatation of sinusoids and congestions. Lesions within proximal and distal tubules were observed in the kidneys. Tissue congestions and severe alterations within glomeruli were visible. DM as a pyrethroid insecticide induced significant increase (P≤0.05) of plasma MDA concentrations after 45 d. A significant increase (P≤0.05) in plasma ALT (after 45 and 60 d) and AST (after 60 d) concentrations was recorded as compared to controls. During the whole experimental period the toxic agent provoked significant DNA damages (P≤0.05), especially in the dominance of classes 3 and 4 of obtained comet. CONCLUSION: DM even at a very low dose displays harmful effects by disrupting hepatic and renal function and causing DNA damages in puberscent female rats. Low doses of DM are hepatotoxic and nephrotoxic.

Parameters for pyrethroid insecticide QSAR and PBPK/PD models for human risk assessment.

In this review we have examined the status of parameters required by pyrethroid QSAR-PBPK/PD models for assessing health risks. In lieu of the chemical,biological, biochemical, and toxicological information developed on the pyrethroids since 1968, the finding of suitable parameters for QSAR and PBPK/PD model development was a monumental task. The most useful information obtained came from rat toxicokinetic studies (i.e., absorption, distribution, and excretion), metabolism studies with 14C-cyclopropane- and alcohol-labeled pyrethroids, the use of known chiral isomers in the metabolism studies and their relation to commercial products. In this review we identify the individual chiralisomers that have been used in published studies and the chiral HPLC columns available for separating them. Chiral HPLC columns are necessary for isomer identification and for developing kinetic values (Vm,, and Kin) for pyrethroid hydroxylation. Early investigators synthesized analytical standards for key pyrethroid metabolites, and these were used to confirm the identity of urinary etabolites, by using TLC. These analytical standards no longer exist, and muste resynthesized if further studies on the kinetics of the metabolism of pyrethroids are to be undertaken.In an attempt to circumvent the availability of analytical standards, several CYP450 studies were carried out using the substrate depletion method. This approach does not provide information on the products formed downstream, and may be of limited use in developing human environmental exposure PBPK/PD models that require extensive urinary metabolite data. Hydrolytic standards (i.e., alcohols and acids) were available to investigators who studied the carboxylesterase-catalyzed hydrolysis of several pyrethroid insecticides. The data generated in these studies are suitable for use in developing human exposure PBPK/PD models.Tissue:blood partition coefficients were developed for the parent pyrethroids and their metabolites, by using a published mechanistic model introduced by Poulin and Thiele (2002a; b) and log DpH 7.4 values. The estimated coefficients, especially those of adipose tissue, were too high and had to be corrected by using a procedure in which the proportion of parent or metabolite residues that are unbound to plasma albumin is considered, as described in the GastroPlus model (Simulations Plus, Inc.,Lancaster, CA). The literature suggested that Km values be adjusted by multiplying Km by the substrate (decimal amount) that is unbound to microsomal or CYPprotein. Mirfazaelian et al. (2006) used flow- and diffusion-limited compartments in their deltamethrin model. The addition of permeability areas (PA) having diffusion limits, such as the fat and slowly perfused compartments, enabled the investigators to bring model predictions in line with in vivo data.There appears to be large differences in the manner and rate of absorption of the pyrethroids from the gastrointestinal tract, implying that GI advanced compartmental transit models (ACAT) need to be included in PBPK models. This is especially true of the absorption of an oral dose of tefluthrin in male rats, in which 3.0-6.9%,41.3-46.3%, and 5.2-15.5% of the dose is eliminated in urine, feces, and bile,respectively (0-48 h after administration). Several percutaneous studies with the pyrethroids strongly support the belief that these insecticides are not readily absorbed, but remain on the surface of the skin until they are washed off. In one articular study (Sidon et al. 1988) the high levels of permethrin absorption through the forehead skin (24-28%) of the monkey was reported over a 7- to 14-days period.Wester et al. (1994) reported an absorption of 1.9% of pyrethrin that had been applied to the forearm of human volunteers over a 7-days period.SAR models capable of predicting the binding of the pyrethroids to plasma and hepatic proteins were developed by Yamazaki and Kanaoka (2004), Saiakhov et al. (2000), Colmenarejo et al. (2001), and Colmenarejo (2003). QikProp(Schrodinger, LLC) was used to obtain Fu values for calculating partition coefficients and for calculating permeation constants (Caco-2, MDCK, and logBBB). ADMET Predictor (Simulations Plus Inc.) provided Vm~,x and Km values for the hydroxylation of drugs/pyrethroids by human liver recombinant cytochrome P450 enzymes making the values available for possible use in PBPK/PD models.The Caco-2 permeability constants and CYP3A4 Vmax and Km values are needed in PBPK/PD models with GI ACAT sub models. Modeling work by Chang et al.(2009) produced rate constants (kcat) for the hydrolysis of pyrethroids by rat serumcarboxylesterases. The skin permeation model of Potts and Guy (1992) was used topredict K, values for the dermal absorption of the 15 pyrethroids.The electrophysiological studies by Narahashi (1971) and others (Breckenridgeet al. 2009; Shafer et al. 2005; Soderlund et al. 2002; Wolansky and Harrill 2008)demonstrated that the mode of action of pyrethroids on nerves is to interfere with the changes in sodium and potassium ion currents. The pyrethroids, being highly lipid soluble, are bound or distributed in lipid bilayers of the nerve cell membrane and exert their action on sodium channel proteins. The rising phase of the action potential is caused by sodium influx (sodium activation), while the falling phase is caused by sodium activation being turned off, and an increase in potassium efflux(potassium activation). The action of allethrin and other pyrethroids is caused by an inhibition or block of the normal currents. An equation by Tatebayashi and Narahashi (1994) that describes the action of pyrethroids on sodium channels was found in the literature. This equation, or some variation of it, may be suitable for use in the PD portion of pyrethroid PBPK models.

Determination of 17 pyrethroid residues in troublesome matrices by gas chromatography/mass spectrometry with negative chemical ionization.

An analytical method with the technique of QuEChERS (quick, easy, cheap, effective, rugged and safe) and gas chromatography (GC)/mass spectrometry (MS) in negative chemical ionization (NCI) has been developed for the determination of 17 pyrethroid pesticide residues in troublesome matrices, including garlic, onion, spring onion and chili. Pyrethroid residues were extracted with acidified acetonitrile saturated by hexane. After a modified QuEChERS clean-up step, the extract was analyzed by GC-NCI/MS in selected ion monitoring (SIM) mode. An isotope internal standard of trans-cypermethrin-D(6) was employed for quantitation. Chromatograms of pyrethroids obtained in all these matrices were relatively clean and without obvious interference. The limits of detection (LODs) ranged from 0.02 to 6 µg kg(-1) and recovery yields were from 54.0% to 129.8% at three spiked levels (20, 40 and 60 µg kg(-1) for chili, and 10, 20 and 30 µg kg(-1) for others) in four different matrices depending on the compounds determined. The relative standard deviations (RSDs) were all below 14%. Isomerization enhancement of pyrethroids in chili extract was observed and preliminarily explained, especially for acrinathrin and deltamethrin.

Integrative assessment of enantioselectivity in endocrine disruption and immunotoxicity of synthetic pyrethroids.

The increasing release of chiral chemicals into the environment dictates attention to a better understanding of enantioselectivity in their human and ecotoxicological effects. Although enantioselectivity has been considered in many recent studies, there is little effort for discerning the connection between different processes, and as such, our current knowledge about chiral contaminants is rather scattered and incoherent. In this study, we simultaneously evaluated enantioselectivity of two chiral pesticides, lambda-cyhalothrin (LCT) and (Z)-cis-bifenthrin (cis-BF), in immunotoxicity to macrophage cells (RAW264.7), and endocrine disruption activity in human breast carcinoma cell line MCF-7. Analysis of cell proliferation, cell viability, apoptosis, and receptor gene expression showed significant differences between the enantiomers of LCT or cis-BF in estrogenic potential and immunocytotoxicity. The selectivity in these effects consistently followed the same direction, with (-)-LCT or 1S-cis-BF displaying a greater activity than its counterpart. The consistency was attributed to interplaying mechanisms in the closely interacting immune and endocrine systems. The underlying interplays suggest that other chiral xenobiotics may also show a directional enantioselectivity in immunotoxicity and endocrine toxicity. Given that many biological processes are inter-related, enantioselectivity may follow specific patterns that can be revealed via integrative assessments as demonstrated in this study.

Environmental concentrations, fate, and risk assessment of pyrethrins and piperonyl butoxide after aerial ultralow-volume applications for adult mosquito management.

One of the most effective ways of managing adult mosquitoes that vector human and animals diseases is the use of ultralow-volume insecticides. Because of concerns about the safety of the insecticides used for the management of adult mosquitoes, we conducted an environmental fate and efficacy study in Princeton and Colusa (both CA, USA) after aerial applications of pyrethrins and piperonyl butoxide (PBO). One hour before application, PBO concentrations in water were 0.008 and 0.2175 microg/L for Princeton and Colusa, respectively. One hour after the spray event in Princeton, the average PBO concentrations were 0.0125 microg/cm2 on ground-deposition pads and 0.1723 microg/L in water samples, with concentrations decreasing significantly over time. One hour after the spray event in Colusa, the average PBO concentrations were 0.0199 microg/cm2 on deposition pads and 1.274 microg/L in water samples, with concentrations decreasing significantly over time. A significant time and location effect for both deposition pads and water samples in Princeton and Colusa was observed (p<0.001 and p=0.014, respectively). Pyrethrins were not detected in nearly all ground and water samples. One hour after application, mortality of Culex tarsalis and Culex pipiens in sentinel cages was significantly higher than at the control site for both locations (p<0.001). Risk quotients for aquatic surrogate species in Princeton and Colusa were 0.002 or less at 1 h after application, which did not exceed the U.S. Environmental Protection Agency risk quotient level of concern for endangered aquatic organisms of 0.05. Our results suggest that the amounts of pyrethrins and PBO deposited on the ground and in water after aerial ULV insecticide applications are lower than those estimated by previous exposure and risk assessments.

A probabilistic screening model for evaluating pyrethroid surface water monitoring data.

Synthetic pyrethroids have been detected in recent California surface water monitoring. Filtration is avoided during sample workup because pyrethroids are extremely hydrophobic, tending to sorb to most surfaces. The resultant analytical pyrethroid concentrations reflect both dissolved pyrethroid and pyrethroid associated with suspended sediment in the water column. Such "whole-water" analytical data are not directly comparable to aquatic acute toxicity effect concentrations measured in laboratory sediment-free water. Consequently, any potential aquatic toxicity risk is indeterminate. In this study a simple probabilistic model was developed to allow a screening-level assessment of pyrethroid whole-water monitoring data. The results suggest that water column toxicity of pyrethroids is possible in California's agriculturally-dominated tributaries, and indicate that additional monitoring to better characterize pyrethroid water-column concentrations are warranted. Model refinement will depend on future work that more firmly establishes the relationship between pyrethroid partitioning and bioavailability, and that addresses the potential influence of dissolved organic carbon on pyrethroid sorption and bioavailability.

Hazard assessment of resmethrin: I. Effects and fate in aquatic systems.

A comparative aquatic hazard assessment of resmethrin was conducted to investigate the need for its restricted use classification by the US. EPA as an adult mosquito control agent. This paper describes the environmental fate and aquatic toxicity of resmethrin. The following paper compares resmethrin to the alternative insecticides. Environmental fate studies indicate that resmethrin has a short photolytic half-life in water (<1 h). Furthermore, it is immobile in soil and biodegradable (half-life = 36.5 d) under aerobic conditions. Laboratory studies with constant 48- to 96-h exposures show it is acutely toxic to fish and invertebrates in the 0.22-15.0 microg/L range. Daphnia magna, pink shrimp (Penaeus duorarum) and rainbow trout (Oncorhynchus mykiss) are the most sensitive and mollusks are the least sensitive species. Chronic laboratory studies indicate that the maximum acceptable toxicant concentrations (MATCs) for resmethrin and D. magna, Pimephales promelas, O. mykiss, and Cyprinodon variegatus are 0.58, 0.52, 0.43, and 10.3 microg/L, respectively. The acute-to-chronic ratios (1.1-7.3) for all species studied indicate that chronic toxicity will not be an issue for resmethrin. Furthermore, the characteristics of acute exposures (48- to 96-h) used in the laboratory will not occur under field conditions because of the short half-life of resmethrin in fresh- and salt-water.