Residue estimation and dietary risk assessment of fenvalerate, novaluron, and profenofos in bell pepper grown under protected and open field conditions.

Residue studies were conducted in bell pepper crops (green and yellow bell pepper) to ensure the safe use of fenvalerate, profenofos, and novaluron (under open field and protected conditions) in randomized block design (RBD) following three applications at a 10-day interval over two consecutive years, 2021 and 2022. A robust analytical method was developed using quick, easy, cheap, effective, rugged, and safe (QuEChERS) extraction and gas chromatography-tandem mass spectrometry (GC-MS/MS) for the determination of pesticide residues in bell pepper samples. The half-lives for fenvalerate were 2.47-2.87 and 2.50-3.03 days on bell pepper under open field conditions, whereas the corresponding values for bell pepper under protected conditions were 3.84-4.58 and 4.17-4.71 days, during 2021 and 2022, respectively. Profenofos displayed half-lives of 2.03-2.65 and 2.15-2.77 days in open field conditions and 3.05-3.89 and 3.16-3.78 days in protected conditions during 2021 and 2022, respectively. Similarly, novaluron had half-lives of 2.87-3.49 and 3.24-3.75 days under protected conditions in 2021 and 2022, respectively. The maximum residue limits (MRLs) were calculated to be 0.6 mg/kg for fenvalerate, while for profenofos it was 0.7 mg/kg on bell pepper under open field conditions at double doses, at the proposed pre-harvest interval (PHI) of 3 days. Likewise, for bell peppers grown under protected conditions, MRLs at the PHI of 3 days were determined to be 0.8 mg/kg for fenvalerate, 0.3 mg/kg for novaluron, and 1.5 mg/kg for profenofos. A dietary risk assessment study indicated that the percentage of acute hazard index (% aHI) was significantly lower than 100, and hazard quotient (HQ) values were below 1, signifying no acute or chronic risk to consumers. These findings underscore the safety of consuming bell peppers treated with fenvalerate, profenofos, and novaluron under the protected and open field conditions.

Validation of an SH-SY5Y Cell-Based Acetylcholinesterase Inhibition Assay for Water Quality Assessment.

The acetylcholinesterase (AChE) inhibition assay has been frequently applied for environmental monitoring to capture insecticides such as organothiophosphates (OTPs) and carbamates. However, natural organic matter such as dissolved organic carbon (DOC) co-extracted with solid-phase extraction from environmental samples can produce false-negative AChE inhibition in free enzyme-based AChE assays. We evaluated whether disturbance by DOC can be alleviated in a cell-based AChE assay using differentiated human neuroblastoma SH-SY5Y cells. The exposure duration was set at an optimum of 3 h considering the effects of OTPs and carbamates. Because loss to the airspace was expected for the more volatile OTPs (chlorpyrifos, diazinon, and parathion), the chemical loss in this bioassay setup was investigated using solid-phase microextraction followed by chemical analysis. The three OTPs were relatively well retained (loss <34%) during 3 h of exposure in the 384-well plate, but higher losses occurred on prolonged exposure, accompanied by slight cross-contamination of adjacent wells. Inhibition of AChE by paraoxon-ethyl was not altered in the presence of up to 68 mgc /L Aldrich humic acid used as surrogate for DOC. Binary mixtures of paraoxon-ethyl and water extracts showed concentration-additive effects. These experiments confirmed that the matrix in water extracts does not disturb the assay, unlike purified enzyme-based AChE assays. The cell-based AChE assay proved to be suitable for testing water samples with effect concentrations causing 50% inhibition of AChE at relative enrichments of 0.5-10 in river water samples, which were distinctly lower than corresponding cytotoxicity, confirming the high sensitivity of the cell-based AChE inhibition assay and its relevance for water quality monitoring. Environ Toxicol Chem 2022;41:3046-3057. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

A non-contact system for intraoperative quantitative assessment of bradykinesia in deep brain stimulation surgery.

BACKGROUND AND OBJECTIVE: Deep brain stimulation (DBS) is an effective treatment for a number of neurological diseases, especially for the advanced stage of Parkinson's disease (PD). Objective assessment of patients' motor symptoms is crucial for accurate electrode targeting and treatment. Existing approaches suffer from subjective variability or interference with voluntary motion. This work is aimed to establish an objective assessment system to quantify bradykinesia in DBS surgery. METHODS: Based on the analysis of the requirements for intraoperative assessment, we developed a system with non-contact measurement, online movement feature extraction, and interactive data analysis and visualization. An optical sensor, Leap Motion Controller (LMC), was taken to detect hand movement in three clinical tasks. A graphic user interface was designed to process, compare and visualize the collected data and assessment results online. Quantified movement features include amplitude, frequency, velocity, their decrement and variability, etc. Technical validation of the system was performed with a motion capture system (Mocap), with respect to data-level and feature-level accuracy and reliability. Clinical validation was conducted with 20 PD patients for intraoperative assessments in DBS surgery. Treatment responses with respect to the bradykinesia movement features were analyzed. Single case analysis and group statistical analysis were performed to examine the differences between preoperative and intraoperative performance, and the correlation between the clinical ratings and the quantified assessment was analyzed. RESULTS: For the movements measured by LMC and Mocap, the average Pearson's correlation coefficient was 0.986, and the mean amplitude difference was 2.11 mm. No significant difference was found for all movement features quantified by LMC and Mocap. For the clinical tests, key movement features showed significant differences between the preoperative baseline and intraoperative performance when the brain stimulation was ON. The assessment results were significantly correlated with the MDS-UPDRS clinical ratings. CONCLUSIONS: The proposed non-contact system has established itself as an objective intraoperative assessment, analysis, and visualization tool for DBS treatment of Parkinson's disease.

MarkerLess Motion Capture: ML-MoCap, a low-cost modular multi-camera setup.

Motion capture systems are extensively used to track human movement to study healthy and pathological movements, allowing for objective diagnosis and effective therapy of conditions that affect our motor system. Current motion capture systems typically require marker placements which is cumbersome and can lead to contrived movements.Here, we describe and evaluate our developed markerless and modular multi-camera motion capture system to record human movements in 3D. The system consists of several interconnected single-board microcomputers, each coupled to a camera (i.e., the camera modules), and one additional microcomputer, which acts as the controller. The system allows for integration with upcoming machine-learning techniques, such as DeepLabCut and AniPose. These tools convert the video frames into virtual marker trajectories and provide input for further biomechanical analysis.The system obtains a frame rate of 40 Hz with a sub-millisecond synchronization between the camera modules. We evaluated the system by recording index finger movement using six camera modules. The recordings were converted via trajectories of the bony segments into finger joint angles. The retrieved finger joint angles were compared to a marker-based system resulting in a root-mean-square error of 7.5 degrees difference for a full range metacarpophalangeal joint motion.Our system allows for out-of-the-lab motion capture studies while eliminating the need for reflective markers. The setup is modular by design, enabling various configurations for both coarse and fine movement studies, allowing for machine learning integration to automatically label the data. Although we compared our system for a small movement, this method can also be extended to full-body experiments in larger volumes.

Assessment of Resistance to Organophosphates and Pyrethroids in Aedes aegypti (Diptera: Culicidae): Do Synergists Affect Mortality?

Aedes aegypti (L.) is the primary vector of Zika, dengue, yellow fever, and chikungunya viruses. Insecticides used in mosquito control can help prevent the spread of vector-borne diseases. However, it is essential to determine insecticide resistance (IR) status before control measures are undertaken. Only the most effective insecticides should be used to avoid ineffective control and/or promotion of IR. Pyrethroids and organophosphates are the most commonly used insecticides for mosquito control. Here, the efficacy of two active ingredients (AIs; permethrin [pyrethroid], chlorpyrifos [organophosphate]), two formulated products (FPs; Biomist [AI: permethrin]) and (Mosquitomist [AI: chlorpyrifos]), and three synergists (piperonyl butoxide, diethyl maleate, S-S-S-tributyl phosphorotrithioate) was evaluated in two Ae. aegypti colonies (pyrethroid resistant and susceptible). Mosquitomist was most effective against the pyrethroid-resistant colony (100% mortality at diagnostic time). Pre-exposure to synergists did not increase the efficacy of AIs against the pyrethroid-resistant colony. Further research is needed to discover how synergists may affect the efficacy of insecticides when used on pyrethroid-resistant mosquitoes.

Assessment of the endocrine-disrupting effects of organophosphorus pesticide triazophos and its metabolites on endocrine hormones biosynthesis, transport and receptor binding in silico.

Triazophos (TAP) was a widely used organophosphorus insecticide in developing countries. TAP could produce specific metabolites triazophos-oxon (TAPO) and 1-phenyl-3-hydroxy-1,2,4-triazole (PHT) and non-specific metabolites diethylthiophosphate (DETP) and diethylphosphate (DEP). The objective of this study involved computational approaches to discover potential mechanisms of molecular interaction of TAP and its major metabolites with endocrine hormone-related proteins using molecular docking in silico. We found that TAP, TAPO and DEP showed high binding affinity with more proteins and enzymes than PHT and DETP. TAP might interfere with the endocrine function of the adrenal gland, and TAP might also bind strongly with glucocorticoid receptors and thyroid hormone receptors. TAPO might disrupt the normal binding of androgen receptor, estrogen receptor, progesterone receptor and adrenergic receptor to their natural hormone ligands. DEP might affect biosynthesis of steroid hormones and thyroid hormones. Meanwhile, DEP might disrupt the binding and transport of thyroid hormones in the blood and the normal binding of thyroid hormones to their receptors. These results suggested that TAP and DEP might have endocrine disrupting activities and were potential endocrine disrupting chemicals. Our results provided further reference for the comprehensive evaluation of toxicity of organophosphorus chemicals and their metabolites.

Environmental risk assessment for sustainable pesticide use in coffee production.

The extensive use of pesticides in agricultural practices has been associated with human health problems and environmental contamination worldwide. Brazil is the largest consumer of pesticides in the world and Espírito Santo State stands out as the second Brazilian producer of coffee. However, there is no information about environmental impact of coffee producing at Itapemirim River Basin (IRB) region, Espírito Santo State, Brazil; hence a simple and quick method using open access softwares (AGROSCRE and ARAquá Web) to estimate surface entrainment and pesticide leaching potential was carried out. AGROSCRE evaluates the contamination risk of superficial and groundwater by Active Ingredients (AIs), using GOSS Method, GUS index and US EPA criteria, while ARAquá Web estimates AI concentrations in water resources, indicating their suitability based on water quality requirements for different uses. Regarding pesticides used in coffee plantations, there is 44.7% chance of surface water and 23.7% chance of groundwater contamination. Results showed that ametryne, cyproconazole, diuron, epoxiconazole, flutriafol, triadimenol and triazophos pose contamination risk to both surface water and groundwater in the IRB region. Of these, 10.5% of the total AIs are triazoles and fall under environmental classes II and III (Product Very/Dangerous to the Environment). The AIs ametryne, thiamethoxam, iprodione, flutriafol, triazophos, endosulfan, triadimenol, cyproconazole, diuron, pendimethalin, chlorpyrifos, copper II hydroxide, etion, epoxiconazole and paraquat dichloride, were found to be potentially toxic, presenting environmental concentrations ranging from 123.40 µg L-1 to 0.14 µg L-1, which are higher than the safety standard for potable water (0.1 µg L-1). With respect to these AIs, chlorpyrifos, ethion and triazophos showed concentrations higher than EC50 values for aquatic invertebrates and ametryne and diuron for algae. Thus, local residents and environment may be at high risk of pesticide exposure, when these AIs are used in coffee plantations next to surface water or groundwater.

Genotoxicity assessment of pesticide profenofos in freshwater fish Channa punctatus (Bloch) using comet assay and random amplified polymorphic DNA (RAPD).

The present study explored the induced genotoxicity (DNA damage) due to organophosphate pesticide profenofos (PFF) after in vivo exposure in freshwater fish Channa punctatus by the use of Comet assay and Random amplified polymorphic DNA (RAPD). The fish specimens were exposed to sub-lethal concentration of 1.16 ppb (50% of LC50) in a semi-static system and the DNA damage was assessed in exposed and control fish. The DNA damage was measured in erythrocytes as the percentage of DNA damage in Comet tails and RAPD technique using oligonucleotide primers of fish specimens exposed to the sublethal concentrations of PFF. The most informative primers in terms of variation in RAPD profile were found to be OPA-01, OPA-03, OPB-02, OPB-01 and OPA-13. Appearance/disappearance of bands and increase/decrease in the band intensity were evident in the RAPD profile of fish specimens exposed to PFF as compared to the control. Findings from the present study suggest that the potential impacts of assessment of the genotoxic impact of pesticide on fish.

Assessment of Tomato (Solanum lycopersicum L.) Producers' Exposure Level to Pesticides, in Kouka and Toussiana (Burkina Faso).

To assess producers' exposure level to pesticides in vegetable production in Burkina Faso, a study was carried out in 2016 and 2017 among 30 tomato producers in the municipalities of Kouka and Toussiana. Eighteen (18) commercial formulations were identified, with more than 50% of pesticides destined for cotton production. Eleven active substances have been identified and the most frequently used are λ-cyhalothrin (35%), acetamiprid (22%) and profenofos (13%). The most commonly used chemical families are pyrethroids (28%) and organophosphates (18%). The study revealed a low level of training for producers, a high use of pesticides according to the Frequency Treatment Indicator, and a very low level of protection used by producers. The Health Risk Index shows that active substances such as methomyl, λ-cyhalothrin and profenofos present very high risk to operators' health. Based on the UK-POEM model, the predictive exposure levels obtained varied from 0.0105 mg/kg body weight/day to 1.7855 mg/kg body weight/day, which is several times higher than the Acceptable Operator Exposure Level. However, the study also shows that exposure can be greatly reduced if the required Personal Protective Equipment is worn. Producers' awareness and training on integrated pest management are necessary to reduce the risks linked to the pesticides use in Burkina Faso.

Risk assessment of agriculture impact on the Frío River watershed and Caño Negro Ramsar wetland, Costa Rica.

The Caño Negro Ramsar wetland is a conservation area of great natural and societal value, located in the lower part of the Frío River watershed in the north of Costa Rica. Its aquatic ecosystems may be considered vulnerable to pollution due to recent changes in land use toward agriculture. In 2011 and 2012, quarterly sampling was done at ten sites located in the middle and lower sections of the Frío River Basin that pass through crop areas and later drain into Caño Negro wetland. Pesticide residues, nitrates, sediment concentrations, and diversity of benthic macroinvertebrates and fish biomarkers were studied in the selected sites. Additionally, risk of toxicity was calculated in two different ways: (1) by using a ratio of MEC to hazard concentrations threshold for 5% of species (HC5) to calculate a risk quotient (RQ), and (2) by using a ratio of MEC to available ecotoxicity data of native fish and cladocera for diazinon and ethoprophos, to obtain a risk quotient for native species (RQns). Results indicated that three out of the ten sites (rivers Thiales, Mónico, and Sabogal) showed variable levels of pollution including six different active ingredients (a.i.) of pesticide formulations (herbicides ametryn, bromacil, and diuron; insecticides cypermethrin, diazinon, and ethoprophos). Moreover, potential adverse effects on fishes in Thiales and Mónico rivers were indicated by cholinesterase (ChE) inhibition and glutathione S-transferase (GST) enhancement. Risk evaluations indicated pesticide residues of ametryn, bromacil, and ethoprophos to be exceeding the limits set by MTR, also RQ was high (>1) in 70% of the positive samples for diuron (most frequently found pesticide in water samples), cypermethrin, diazinon, and ethoprophos, and RQns was high for diazinon. Therefore, these substances might be of major concern for the ecological health of aquatic ecosystems in the middle basin of the Frío River. The most critical site was Mónico River, which had the highest pollution (75% detection samples with 3-5 a.i.) and highest calculated risk (RQ > 1 in 75% of the samples). This is also the river that most directly drains into the protected wetland. Even though pesticide pollution in this area is not as severe as in other parts of Costa Rica, it is imperative that measures are taken, particularly in the surroundings of Mónico River, in order to diminish and mitigate possible detrimental effects to biota in Caño Negro Ramsar Site.

Sensitivity assessment of sea lice to chemotherapeutants: Current bioassays and best practices.

Traditional bioassays are still necessary to test sensitivity of sea lice species to chemotherapeutants, but the methodology applied by the different scientists has varied over time in respect to that proposed in "Sea lice resistance to chemotherapeutants: A handbook in resistance management" (2006). These divergences motivated the organization of a workshop during the Sea Lice 2016 conference "Standardization of traditional bioassay process by sharing best practices." There was an agreement by the attendants to update the handbook. The objective of this article is to provide a baseline analysis of the methodology for traditional bioassays and to identify procedures that need to be addressed to standardize the protocol. The methodology was divided into the following steps: bioassay design; material and equipment; sea lice collection, transportation and laboratory reception; preparation of dilution; parasite exposure; response evaluation; data analysis; and reporting. Information from the presentations of the workshop, and also from other studies, allowed for the identification of procedures inside a given step that need to be standardized as they were reported to be performed differently by the different working groups. Bioassay design and response evaluation were the targeted steps where more procedures need to be analysed and agreed upon.

Seasonal and occupational trends of five organophosphate pesticides in house dust.

Since 1998, the University of Washington's Center for Child Environmental Health Risks Research has followed a community-based participatory research strategy in the Lower Yakima Valley of Washington State to assess pesticide exposure among families of Hispanic farmworkers. As a part of this longitudinal study, house dust samples were collected from both farmworker and non-farmworker households, across three agricultural seasons (thinning, harvest and non-spray). The household dust samples were analyzed for five organophosphate pesticides: azinphos-methyl, phosmet, malathion, diazinon, and chlorpyrifos. Organophosphate pesticide levels in house dust were generally reflective of annual use rates and varied by occupational status and agricultural season. Overall, organophosphate pesticide concentrations were higher in the thinning and harvest seasons than in the non-spray season. Azinphos-methyl was found in the highest concentrations across all seasons and occupations. Farmworker house dust had between 5- and 9-fold higher concentrations of azinphos-methyl than non-farmworker house dust. Phosmet was found in 5-7-fold higher concentrations in farmworker house dust relative to non-farmworker house dust. Malathion and chlorpyriphos concentrations in farmworker house dust ranged between 1.8- and 9.8-fold higher than non-farmworker house dust. Diazinon showed a defined seasonal pattern that peaked in the harvest season and did not significantly differ between farmworker and non-farmworker house dust. The observed occupational differences in four out of five of the pesticide residues measured provides evidence supporting an occupational take home pathway, in which workers may bring pesticides home on their skin or clothing. Further, these results demonstrate the ability of dust samples to inform the episodic nature of organophosphate pesticide exposures and the need to collect multiple samples for complete characterization of exposure potential.

An extensive cocktail approach for rapid risk assessment of in vitro CYP450 direct reversible inhibition by xenobiotic exposure.

Acute exposure to environmental factors strongly affects the metabolic activity of cytochrome P450 (P450). As a consequence, the risk of interaction could be increased, modifying the clinical outcomes of a medication. Because toxic agents cannot be administered to humans for ethical reasons, in vitro approaches are therefore essential to evaluate their impact on P450 activities. In this work, an extensive cocktail mixture was developed and validated for in vitro P450 inhibition studies using human liver microsomes (HLM). The cocktail comprised eleven P450-specific probe substrates to simultaneously assess the activities of the following isoforms: 1A2, 2A6, 2B6, 2C8, 2C9, 2C19, 2D6, 2E1, 2J2 and subfamily 3A. The high selectivity and sensitivity of the developed UHPLC-MS/MS method were critical for the success of this methodology, whose main advantages are: (i) the use of eleven probe substrates with minimized interactions, (ii) a low HLM concentration, (iii) fast incubation (5min) and (iv) the use of metabolic ratios as microsomal P450 activities markers. This cocktail approach was successfully validated by comparing the obtained IC50 values for model inhibitors with those generated with the conventional single probe methods. Accordingly, reliable inhibition values could be generated 10-fold faster using a 10-fold smaller amount of HLM compared to individual assays. This approach was applied to assess the P450 inhibition potential of widespread insecticides, namely, chlorpyrifos, fenitrothion, methylparathion and profenofos. In all cases, P450 2B6 was the most affected with IC50 values in the nanomolar range. For the first time, mixtures of these four insecticides incubated at low concentrations showed a cumulative inhibitory in vitro effect on P450 2B6.

Dissipation pattern and risk assessment studies of triazophos residues on capsicum (Capsicum annuum L.) using GLC-FPD and GC-MS.

The present study was carried out to observe the dissipation pattern of triazophos on capsicum and risk assessment of its residues on human beings and to suggest a waiting period for the safety of consumers. Following two applications of triazophos (Truzo 40 EC) at 500 and 1000 g a.i. ha(-1), the average initial deposits were found to be 3.61 and 6.26 mg kg(-1), respectively. These residues dissipated below the limit of quantification (LOQ) of 0.05 mg kg(-1) in 10 and 15 days at the recommended and double the recommended dosages, respectively. The calculated values of half-life were 2.31 and 2.14 days at recommended and double the recommended dosages, respectively. Theoretical maximum residue contribution (TMRC) values were found to be 28.8 and 41.6 µg person(-1) day(-1) at 500 and 1000 g a.i. ha(-1), respectively, and found to be below the maximum permissible intake on capsicum fruit on the 7th day. Therefore, a waiting period of 7 days is suggested for consumption of capsicum sprayed with triazophos at the recommended dosages.

Mechanism of Resistance Acquisition and Potential Associated Fitness Costs in Amyelois transitella (Lepidoptera: Pyralidae) Exposed to Pyrethroid Insecticides.

The polyphagous navel orangeworm, Amyelois transitella (Walker) (Lepidoptera: Pyralidae), is the most destructive pest of nut crops, including almonds and pistachios, in California orchards. Management of this insect has typically been a combination of cultural controls and insecticide use, with the latter increasing substantially along with the value of these commodities. Possibly associated with increased insecticide use, resistance has been observed recently in navel orangeworm populations in Kern County, California. In studies characterizing a putatively pyrethroid-resistant strain (R347) of navel orangeworm, susceptibility to bifenthrin and ß-cyfluthrin was compared with that of an established colony of susceptible navel orangeworm. Administration of piperonyl butoxide and S,S,S-tributyl phosphorotrithioate in first-instar feeding bioassays with the pyrethroids bifenthrin and ß-cyfluthrin produced synergistic effects and demonstrated that cytochrome P450 monooxygenases and carboxylesterases contribute to resistance in this population. Resistance is therefore primarily metabolic and likely the result of overexpression of specific cytochrome P450 monooxygenases and carboxylesterase genes. Resistance was assessed by median lethal concentration (LC50) assays and maintained across nine generations in the laboratory. Life history trait comparisons between the resistant strain and susceptible strain revealed significantly lower pupal weights in resistant individuals reared on the same wheat bran-based artificial diet across six generations. Time to second instar was greater in the resistant strain than the susceptible strain, although overall development time was not significantly different between strains. Resistance was heritable and may have an associated fitness cost, which could influence the dispersal and expansion of resistant populations in nut-growing areas in California.

Longitudinal assessment of occupational exposures to the organophosphorous insecticides chlorpyrifos and profenofos in Egyptian cotton field workers.

Chlorpyrifos (CPF) and profenofos (PFF) are organophosphorus (OP) insecticides that are applied seasonally in Egypt to cotton fields. Urinary trichloro-2-pyridinol (TCPy), a specific CPF metabolite, and 4-bromo-2-chlorophenol (BCP), a specific PFF metabolite, are biomarkers of exposure, while inhibition of blood butyrylcholinesterase (BChE) and acetylcholinesterase (AChE) activities are effect biomarkers that may be associated with neurotoxicity. Urinary TCPy and BCP and blood BChE and AChE activities were measured in 37 adult Egyptian Ministry of Agriculture workers during and after 9-17 consecutive days of CPF application followed by an application of PFF (9-11 days), and a second CPF application (5 days) in 2008. During the OP applications, urinary TCPy and BCP levels were significantly higher than baseline levels, remained elevated following the application periods, and were associated with an exposure related inhibition of blood BChE and AChE. Analysis of blood AChE levels before and after the PFF application period suggests that individual workers with peak BCP levels greater than 1000 µg/g creatinine exhibited further inhibition of blood AChE with PFF application, demonstrating that PFF exposure had a negative impact on AChE activity in this highly exposed worker population. While large interindividual differences in exposure were observed throughout this longitudinal study (peak urinary BCP and peak TCPy levels for individuals ranging from 13.4 to 8052 and 16.4 to 30,107 µg/g creatinine, respectively), these urinary biomarkers were highly correlated within workers (r=0.75, p<0.001). This suggests that the relative exposures to CPF and PFF were highly correlated for a given worker. The variable exposures between job classification and work site suggest that job title and work location should not be used as the sole basis for categorizing OP exposures when assessing neurobehavioral and other health outcomes in Egyptian cotton field workers. Together, these findings will be important in educating the Egyptian insecticide application workers in order to encourage the development and implementation of work practices and personal protective equipment to reduce their exposure to CPF and PFF.

The combined toxicity assessment of carp (Cyprinus carpio) acetylcholinesterase activity by binary mixtures of chlorpyrifos and four other insecticides.

Mixtures of organophosphate (OP) and carbamate (CB) insecticides are commonly detected in freshwater habitats. These insecticides inhibit the activity of acetylcholinesterase (AChE) and have potential to interfere with behaviors that may be essential for survival of species. Although the effects of individual anticholinesterase insecticides on aquatic species have been studied for decades, the combined toxicity of mixtures is still poorly understood. In the present study, we assessed whether pesticides in a mixture act in isolation (resulting in additive AChE inhibition) or whether components interact to produce either antagonistic or synergistic toxicity. Brain AChE inhibition in carp (Cyprinus carpio L.) exposed to a series of concentrations of the OP (chlorpyrifos, malathion and triazophos) as well as the CB (fenobucarb and carbosulfan) were measured. The concentration addition (CA) model and the isobole method were used to determine whether toxicological responses to binary mixtures of pesticides. In 50:50 % effect mixtures, the observed combined toxicity of chlorpyrifos and malathion was significantly higher than observed and was considered as synergistic. For equivalent dose mixtures, when chlorpyrifos mixed with fenobucarb or malathion, the observed toxicities were significantly higher than predicted, suggesting synergistic joint actions. The rest five binary combinations exhibited concentration additive or slight antagonistic joint actions. The CA model and the isobole method provided estimates of mixture toxicity that did not markedly underestimate the measured toxicity, therefore these methods are suitable to use in ecological risk assessments of pesticide mixtures.

A QuEChERS-based extraction method for the residual analysis of pyraclofos and tebufenpyrad in perilla leaves using gas chromatography: application to dissipation pattern.

The objective of this work was to establish a simple extraction method for the residual analysis of pyraclofos and tebufenpyrad in Perilla leaves. A QuEChERS (quick, easy, cheap, effective, rugged and safe) method was used for extraction using ethyl acetate as an extraction solvent, and cleanup was carried out using dispersive solid-phase extraction technique. The samples were analyzed using gas chromatography with nitrogen phosphorous detector and confirmed by gas chromatography-mass spectrometry. The linearity was excellent (r(2) = 1.0) in matrix-matched calibration for both pesticides. The recoveries at two fortification levels were 80.76-95.38% with relative standard deviation lower than 5%. The limits of detection and limits of quantification were 0.01 and 0.033 mg/kg for both pesticides, respectively. The results revealed that the dissipation pattern of pyraclofos and tebufenpyrad followed first-order kinetics. The pyraclofos and tebufenpyrad residues declined to a level below the maximum residue limits within 14 day between the last application and harvesting. We suggest that pyraclofos and tebufenpyrad could be used efficiently on perilla leaves under the recommended dosage conditions.

Assessment of long-term subacute exposure to dimethoate by hair analysis of dialkyl phosphates DMP and DMTP in exposed rabbits: The effects of dose, dose duration and hair colour.

Hair analysis for dialkyl phosphates' (DAPs) residues could provide a measure of chronic exposure to organophosphate pesticides (OPs). The aim of this study was to determine whether these metabolites can be internally incorporated into the hair of rabbits exposed to dimethoate and also to investigate the influence of dose and dose duration of this OP, as well as the effect of hair colour on the concentrations of its DAPs in hair. Two-coloured rabbits were daily exposed to dimethoate (0, 12 or 24mgkg(-1) body weight) via their drinking water. Hair samples of both colours were obtained 4 and 6 months after the beginning of exposure from the back of all treated rabbits, and each hair colour sample was analyzed for dimethyl phosphate (DMP) and dimethyl thiophosphate (DMTP) by gas chromatography-mass spectrometry (GC-MS). Analysis revealed the incorporation of these metabolites into the rabbit hair in a dose-dependent manner. The mean concentrations found ranged from 0.18 to 0.77ngmg(-1) for DMP and from 0.43 to 1.53ngmg(-1) for DMTP. Mixed results for the significance of the relationship between dose duration and the levels of the two DAPs in hair are observed. Hair pigmentation does not appear to affect the concentration values of DMTP, whereas it seems to be a critical factor in the incorporation of DMP into hair. These data confirm the ability of hair testing to assess chronic OP exposure by the detection of DAPs.

A rapid, cost-effective method for analyzing organophosphorus pesticide metabolites in human urine for counter-terrorism response.

Organophosphorus (OP) pesticides are used as insecticides in agriculture and pest control and are often called "junior strength" nerve agents because they share the same mechanism of toxicity. OP pesticides are metabolized to dialkylphosphates and other metabolites, which are excreted in urine. In case of a terrorism incident involving widely available OP pesticides, an occurrence that may be likely given their widespread availability, a rapid, accurate, and cost-effective method for detecting exposure is required. We have evaluated several analytical methods to determine the most reliable and cost-effective methods for incident response. Our comparisons have included different internal standards (isotopically labeled standards versus chemically similar surrogate standards), different isolation techniques (some of which are automatable), and different analysis platforms. We found that isotopically labeled standards were a necessity to provide accurate quantification; the chemically similar surrogate was not suitable as an internal standard. The most sensitive and precise method uses isotopically labeled standards with gas chromatography-tandem mass spectrometry analysis. However, the most cost-effective method employed isotopically labeled standards with gas chromatography-single quadrupole-mass spectrometry using a less expensive mass selective detector. Because this method is lower in cost, it may be a more viable option for equipping multiple laboratories with chemical-terrorism response capabilities.