Comparison of supercritical fluid chromatography-tandem mass spectrometry and liquid chromatography-tandem mass spectrometry for the stereoselective analysis of chlorfenvinphos and dimethylvinphos in tobacco.

This study used reversed-phase liquid chromatography-tandem mass spectrometry and supercritical fluid chromatography-tandem mass spectrometry for determination of the stereoisomers of chlorfenvinphos and dimethylvinphos in tobacco. Tobacco samples were extracted and purified with a modified quick, easy, cheap, effective, rugged, and safe technique using spherical carbon. The performance of both methodologies was comprehensively compared in terms of methods validation parameters (separation efficiency, linearity, selectivity, recovery, repeatability, sensitivity, matrix effect, etc.). Under optimized conditions, the calibration curves of the stereoisomers of chlorfenvinphos and dimethylvinphos in the range of 10-500 ng/mL showed excellent linearity with R2 ≥ 0.997 in both methods. The adequate recoveries of analytes from three different spiked tobaccos were obtained using reversed-phase liquid chromatography-tandem mass spectrometry (86.1-95.7%) as well as supercritical fluid chromatography-tandem mass spectrometry (86.5-94.0%). The relative standard deviations for spiked samples were all below 7.0%. Compared with supercritical fluid chromatography-tandem mass spectrometry, lower matrix effects and LODs can be obtained in reversed-phase liquid chromatography-tandem mass spectrometry.

Development and Validation of a Gas Chromatography-Mass Spectrometry Method for Determining Acaricides in Bee Pollen.

Pesticides can be found in beehives for several reasons, including contamination from surrounding crops or for their use by beekeepers, which poses a risk to bee ecosystems and consumers. Therefore, efficient and sensitive methods are needed for determining pesticide residues in bee products. In this study, a new analytical method has been developed and validated to determine seven acaricides (atrazine, chlorpyrifos, chlorfenvinphos, α-endosulfan, bromopropylate, coumaphos, and τ-fluvalinate) in bee pollen using gas chromatography coupled to mass spectrometry. After an optimization study, the best sample treatment was obtained when using a modified QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) method employing an ethyl acetate and cyclohexane as the extractant mixture, and a mixture of salts for the clean-up step. A chromatographic analysis (<21 min) was performed in an Agilent DB-5MS column, and it was operated under programmed temperature conditions. The method was fully validated in terms of selectivity, limits of detection (0.2-3.1 µg kg-1) and quantification (0.6-9.7 µg kg-1), linearity, matrix effect (<20% in all cases), trueness (recoveries between 80% and 108%), and precision. Finally, the proposed method was applied to analyze commercial bee pollen samples, and some of the target pesticides (chlorfenvinphos, α-endosulfan, coumaphos, and τ-fluvalinate) were detected.

Evolution of acaricide resistance of Rhipicephalus decoloratus on commercial farms in South Africa.

The development of tick resistance to chemical control plays a major role in the increasing global economic impact of ticks on cattle farming. Reports on acaricide resistance of Rhipicephalus decoloratus, endemic to Africa and South Africa, are relatively few compared to the closely related and globally distributed Rhipicephalus microplus. In South Africa, ectoparasite control became the sole responsibility of each commercial producer when compulsory dipping was phased out from 1984. Different acaricidal management strategies resulted in the simultaneous development of resistance to various acaricide groups. The establishment of a Pesticide Resistance Testing Facility provided the opportunity to test Rhipicephalus (Boophilus) populations, submitted from all over South Africa, for resistance where failure of chemical control was experienced. The number of populations resistant to cypermethrin (CM) was significantly higher than those tested as resistant to amitraz (AM), or chlorfenvinphos (CFVP). No significant difference was found between the number of populations resistant to AM and CFVP. The evolution of R. decoloratus resistance at the end of a 12 year period indicated a stable but high prevalence of 90% overall resistance to CM. The same trend was seen for AM-resistant R. decoloratus populations but at a lower level of just over 40%. In contrast, CFVP resistant R. decoloratus populations showed a decreasing trend with near-total reversion to susceptibility. Multi-resistance was present in more than 50% of populations tested with the highest incidence in the Eastern Cape, KwaZulu-Natal, and Western Cape provinces.

The effect of two bromfenvinphos impurities: BDCEE and ß-ketophosphonate on oxidative stress induction, acetylcholinesterase activity, and viability of human red blood cells.

Numerous research works have shown that synthesis of pesticides leads to the formation of impurities that may substantially enhance pesticide toxicity. In this study, the effect of manufacturing impurities of pesticide bromfenvinphos (BFVF) such as 1-bromo-2-(2,4-dichlorophenyl)-2-ethoxy ethene (BDCEE) and diethyl [2-(2,4-dichlorophenyl)-2-oxo-ethyl] phosphonate (ß-ketophosphonate) on human erythrocytes, being significantly exposed to xenobiotics has been studied. The cells were treated with the compounds studied in the concentrations ranging from 0.1 µM to 250 µM for 4 h. In order to assess the effect of BDCEE and ß-ketophosphonate on red blood cells hemolytic changes, changes in cell size (FSC parameter) and oxidation of hemoglobin were studied. Moreover, alterations in reactive oxygen species (ROS) formation, reduced glutathione (GSH) level and acetylcholinesterase (AChE) activity were determined. BDCEE induced an increase in ROS level and caused strong oxidation of hemoglobin as well as a slight change in erythrocytes size and hemolysis, while it did not change GSH level and AChE activity. ß-ketophosphonate has not been shown to affect most parameters studied, but it strongly reduced AChE activity. Because changes in the parameters examined were noted at low concentrations of BFVF impurities (5-250 µM), those substances should not negatively affect on red blood cells of humans environmentally exposed to this pesticide.

High intensity of Tunga penetrans infection causing severe disease among pigs in Busoga, South Eastern Uganda.

BACKGROUND: Towards the improvement of stakeholders' awareness of animal tungiasis, we report 10 unusual severe clinical cases of pig tungiasis which were associated with very high infection intensities of T. penetrans in an endemic area. RESULTS: Morbidity of ten pigs with high sand flea intensities detected during high transmission seasons in an endemic area in Busoga sub region, Uganda is described in detail. The cases of pigs presented with a very high number of embedded sand fleas (median = 276, range = 141-838). Acute manifestations due to severe tungiasis included ulcerations (n = 10), abscess formation (n = 6) and lameness (n = 9). Chronic morphopathological presentations were overgrowth of claws (n = 5), lateral deviation of dew claws (n = 6), detachment (n = 5) or loss of dew claws (n = 1). Treatment of severe cases with a topical insecticidal aerosol containing chlorfenvinphos, dichlorvos and gentian violet resolved acute morbidity and facilitated healing by re-epithelialisation. CONCLUSIONS: The presentations of tungiasis highlighted in this report show that high intensities of embedded T. penetrans can cause a severe clinical disease in pigs. Effective tungiasis preventive measures and early diagnosis for treatment could be crucial to minimize its effects on animal health.

Bromfenvinphos induced suicidal death of human erythrocytes.

The organophosphorus pesticide bromfenvinphos ((E,Z)-O,O-diethyl-O-[1-(2,4-dichlorophenyl)-2-bromovinyl] phosphate) has been shown to decrease hematocrit and hemoglobin levels in blood presumably by triggering oxidative stress of erythrocytes. Oxidative stress is known to activate erythrocytic Ca(2+) permeable unselective cation channels leading to Ca(2+) entry and increase of cytosolic Ca(2+) activity ([Ca(2+)]i), which in turn triggers eryptosis, the suicidal death characterized by cell shrinkage and cell membrane scrambling with phosphatidylserine translocation to the erythrocyte surface. The present study explored, whether and how bromfenvinphos induces eryptosis. To this end, phosphatidylserine exposure at the cell surface was estimated from annexin-V-binding, cell volume from forward scatter, hemolysis from hemoglobin release, [Ca(2+)]i from Fluo3-fluorescence, and ROS formation from DCFDA dependent fluorescence. As a result, a 48hour exposure of human erythrocytes to bromfenvinphos (≥100µM) significantly increased the percentage of annexin-V-binding cells, significantly decreased forward scatter, significantly increased Fluo3-fluorescence, and significantly increased DCFDA fluorescence. The effect of bromfenvinphos on annexin-V-binding and forward scatter was significantly blunted, but not abolished by removal of extracellular Ca(2+). In conclusion, bromfenvinphos triggers cell shrinkage and phospholipid scrambling of the erythrocyte cell membrane, an effect in part due to stimulation of ROS formation and Ca(2+) entry.

Oxidative stress in human erythrocytes treated with bromfenvinphos and its impurities.

Bromfenvinphos (BFVF) is an organophosphorus (OP) pesticide which was widely used in agriculture and veterinary practice. During synthesis of this insecticide five main impurities are formed: dihydro-bromfenvinphos, dibromo-bromfenvinphos, 2,4-dichlorophenacyl bromide, 2,4-dichlorophenacylidene bromide and 2,4-dichlorophenacylidyne bromide, which can be present in technical grade bromfenvinphos in amounts from 0.1 to 4%. The aim of this study was to examine the influence of bromfenvinphos and its manufacturing impurities on parameters of oxidative stress, the activity of antioxidative enzymes and the level of reduced glutathione. Human erythrocytes were incubated with bromfenvinphos and its impurities in the concentrations range from 0.5 to 500 µM for 1 h. This study indicated that 2,4-dichlorophenacyl derivatives more strongly oxidized analyzed parameters in human erythrocytes than bromfenvinphos. Investigated compounds caused an increase in lipid peroxidation and oxidation of fluorescent probe DCFH2 - the strongest pro-oxidative changes were provoked by 2,4-dichlorophenacyl bromide. None of the compounds studied in the concentrations from 0.5 to 500 µM changed the activity of SOD and only 2,4-dichlorophenacyl decreased activity of CAT. The level of GSH was only altered by 2,4-dichlorophenacyl derivatives. It was observed that increasing number of bromine atoms in the side chain of those derivatives was associated with decreased GSH level.

Alterations in gills of Lepomis gibbosus, after acute exposure to several xenobiotics (pesticide, detergent and pharmaceuticals): morphometric and biochemical evaluation.

In recent decades, scientific research about the effects of anthropogenic xenobiotics on non-target organisms has increased. Among the likely effects, some studies reported the evaluation of biochemical and morphological changes in specific tissues or organs of fishes, such as gills, which are key organs for the direct action of pollutants in the aquatic environment. This work intended to assess biochemical [oxidative stress/phase II conjugation isoenzymes glutathione S-transferase (GSTs)] and morphological [secondary lamellar length (SLL), secondary lamellar width (SLW), interlamellar distance (ID), basal epithelial thickness (BET) and proportion of the secondary lamellae available for gas exchange (PAGE)] changes in gills, after acute exposure to the pesticide chlorfenvinphos, the detergent sodium dodecylsulphate (SDS) and to the anticholinesterasic pharmaceuticals (neostigmine and pyridostigmine). Our results point to a significant, eventually hormetic, effect in the activity of GSTs following exposure to chlorfenvinphos that significantly increased the activity of GSTs at concentration of 0.2 mg/L. The activity of GSTs increased significantly after exposure to 100 mg/L of neostigmine. Considering the morphometric analysis of the gills, the data obtained showed that chlorfenvinphos exerted mainly minor architectural alterations in gills, with the exception of the highest tested concentration of chlorfenvinphos that produced also a slight decrease of the PAGE. The overall conclusions point to a null or negligible toxicity of the selected toxicants towards L. gibbosus, which may be reverted if exposure is withdrawn.

[Serum glucose concentration in subacute intoxication with chlorpyrifos - organophosphate insecticide]. / Stezenie glukozy w surowicy krwi w podostrym zatruciu chlorpyrifosem - insektycydem fosforoorganicznym.

BACKGROUND: Epidemiological studies suggest that exposure to organophosphate insecticides enhances the risk of various diseases, including neurological disorders, e.g. Parkinson's or Alzheimer's disease, arteriosclerosis and diabetes mellitus. For this reason the aim of the presented study was to estimate serum concentration of glucose in subchronic intoxication with low doses of chlorpyrifos, an organophosphate insecticide. MATERIALS AND METHODS: The rats received chlorpyrifos at a daily dose of 0.2, 2 or 5 mg/kg b.w./day for 14 or 28 days. For biochemical determinations of serum glucose in the rats ready-to-use kit was applied. RESULTS: In subacute intoxication with chlorpyrifos the increased serum concentration of glucose was observed after 14 days of intoxication with the highest dose (5 mg/kg b.w.) and after 28 days of intoxication with all dose levels used. CONCLUSIONS: The results of this study showing the increased concentration of serum glucose in subacute intoxication with low doses of chlorpyrifos, as well as the literature data suggest that exposure to organophosphate insecticides can increase the risk of diabetes mellitus. It may thus be concluded that people occupationally exposed to these compounds should be subjected to diagnostic tests for early detection of diabetes.

Pesticide residues in bee bread, propolis, beeswax and royal jelly - A review of the literature and dietary risk assessment.

Due to pollinator decline observed worldwide, many studies have been conducted on the pesticide residue content of apicultural products including bee bread, propolis, beeswax and royal jelly. These products are consumed for their nutraceutical properties, although, little information is available on the human health risk posed by pesticides present in them. In our research, studies dealing with the pesticide contamination of the above-mentioned hive products are reviewed. Dietary exposures were calculated based on the recommended daily intake values and concentration data reported by scientific studies. Potential acute and chronic health risk of consumers were evaluated by comparing the exposure values with health-based guidance values. Available data indicate that a wide range of pesticide residues, especially acaricides may accumulate in bee bread, propolis and beeswax, up to concentration levels of more thousand µg/kg. Based on our observations, tau-fluvalinate, coumaphos, chlorfenvinphos, chlorpyrifos and amitraz are commonly detected pesticide active substances in beehive products. Our estimates suggest that coumaphos and chlorfenvinphos can accumulate in beeswax to an extent that pose a potential health risk to the consumers of comb honey. However, it appears that pesticide residues do not transfer to royal jelly, presumably due to the filtering activity of nurse bees during secretion.

Status of Acaricide Resistance and Detecting the Knockdown Resistance Mutation T2134A in the Cattle Tick Rhipicephalus microplus (Acari: Ixodidae) from Northeastern Mexico.

Rhipicephalus microplus is the most important tick in veterinary medicine, given its repercussions on animal production. The principal strategy to avoid adverse effects associated with R. microplus is the chemical control of tick populations through organosynthetic acaricides. Therefore, monitoring susceptibility to acaricides is paramount in any control program. This study aimed to analyze the resistance status of 2 populations of R. microplus from northeastern Mexico to the organochlorine (OC) lindane, organophosphates (OP) coumaphos, chlorfenvinphos, diazinon, and chlorpyrifos, and the synthetic pyrethroids (SPs) flumethrin, deltamethrin, and cypermethrin. Discriminating doses (DD) of each acaricide were used in the larval packet bioassay (LPT). Additionally, the presence of the knockdown resistance (kdr) mutation T2134A associated with pyrethroid resistance was evaluated using allele-specific polymerase chain reaction (PCR). The populations of R. microplus showed a high frequency of resistance to SP, with mortality rates of less than 5%; they also showed resistance to the OPs (diazinon and chlorpyrifos) with mortality rates ranging from 1.29% to 34.62%; meanwhile, they were susceptible to coumaphos and chlorfenvinphos. Mortality rates higher than 66% were observed for lindane, indicating susceptibility. The mutant allele of the kdr mutation T2134A was detected in 75% and 100% of the pools analyzed. The populations studied presented a highly resistant profile to pyrethroids, with the presence of the kdr mutant allele A2134. The susceptibility to the organophosphates such as coumaphos and chlorfenvinphos of R. microplus from northeastern Mexico should be noted.

Variation in effects of four OP insecticides on photosynthetic pigment fluorescence of Chlorella vulgaris Beij.

Effects of the insecticides quinalphos, chlorfenvinphos, dimethoate and phorate on photosystem activity of Chlorella vulgaris were investigated by different chlorophyll fluorescence measurements. Exposure to each of the insecticides increased the proportion of inactivated PS II reaction center. Quinalphos and chlorfenvinphos caused OJIP fluorescence reduction at all levels by decreasing the proportion of Q(A)-reducing PS II reaction centers (RCs). The other two insecticides affected OJIP fluorescence rise by hindering the electron transport beyond Q(A). Insecticide treatment resulted in decrease of the density of active RC and performance indices (PI) by enhanced dissipated energy flux per active RC. Antenna size was severely minimized by quinalphos and chlorfenvinphos treatment whereas other two insecticides had no such effect. Each insecticide treatment caused increase of photosystem antenna/core and PS II/PS I fluorescence ratios. Quinalphos and chlorfenvinphos affected the donor sides of photosystems whereas dimethoate and phorate inhibited electron transfer beyond Q(A) (acceptor side).

[Paraoxonase activity and lipid peroxides concentration in serum of rats subchronically intoxicated with chlorpyrifos--organophosphate insecticide]. / Atywnosc paraoksonazy i stezenie nadtlenków lipidów w surowicy krwi szczurów w podostrym zatruciu chlorpyrifosem--insektycydem fosforoorganicznym.

BACKGROUND: Toxicity of organophosphate insecticides is mainly due to the inhibition of acetylcholinesterase (AChE). However, organophosphate insecticides in acute, as well as in chronic and subchronic intoxication may lead to oxidative stress causing the enhancement of lipid peroxidation and changing the activities of antioxidative enzymes. Paraoxonase PON1 is synthesized by the liver. This enzyme hydrolyzes organophosphate compounds, phospholipid hydroperoxides and cholesterol ester hydroperoxides. Its role as an antioxidant has also been suggested. For this reason the aim of the work was to estimate the activity of paraoxonase and the level of serum lipid peroxides in the rats subchronically intoxicated with chlorpyrifos. MATERIALS AND METHODS: The animals received chlorpyrifos at a single daily dose of 0.2, 2 or 5 mg/kg b.w./day for 14 days. For biochemical determinations of paraoxonase activity in serum of rats, Aryloesterase/Paraoksonase Assay Kit (ZeptoMetrix Corporation Buffalo, USA) and for lipid peroxides level, LPO-586 (OXIS International, Foster City, Calif., USA) were used. RESULTS: Chlorpyrifos administration resulted in a decreased activity of paraoxonase in serum. The highest decrease was observed after administration of chlorpyrifos in doses 2 and 5 mg/kg b.w./day. In the intoxication with the highest insecticide dose under study the decreased paraoxonase activity was accompanied by the increased level of lipid peroxides. CONCLUSIONS: In view of the literature data, the finding that low doses of chlorpyrifos lead to statistically significant decrease in paraoxonase activity in serum of rats provides evidence that exposure to organophosphate insecticides induces oxidative stress. It also suggests the need to take into consideration a possible development of arteriosclerosis, hypercholesterolemia and diabetes mellitus in people exposed to these compounds.

Study of the chlorfenvinphos pesticide removal under different anodic materials and different reactor configuration.

The present manuscript focuses on the study of the electrochemical oxidation of the insecticide Chlorfenvinphos (CVP). The assays were carried out under galvanostatic conditions using boron-doped diamond (BDD) and low-cost tin dioxide doped with antimony (Sb-doped SnO2) as anodes. The influence of the operating variables, such as applied current density, presence or absence of a cation-exchange membrane and concentration of supporting electrolyte, was discussed. The results revealed that the higher applied current density the higher degradation and mineralization of the insecticide for both anodes. The presence of the membrane and the highest concentration of Na2SO4 studied (0.1 M) as a supporting electrolyte benefited the oxidation process of CVP using the BDD electrode, while with the ceramic anode the elimination of CVP was lower under these experimental conditions. Although the BDD electrode showed the best performance, ceramic anodes appear as an interesting alternative as they were able to degrade CVP completely for the highest applied current density values. Toxicity tests revealed that the initial solution of CVP was more toxic than the samples treated with the ceramic electrode, while using the BDD electrode the toxicity of the sample increased.

Acaricidal activity of carvacrol and thymol on acaricide-resistant Rhipicephalus microplus (Acari: Ixodidae) populations and combination with cypermethrin: Is there cross-resistance and synergism?

This study evaluated the acaricidal activity of thymol and carvacrol on Rhipicephalus microplus populations with different resistance profiles and investigated the synergistic effect of combinations of these monoterpenes with cypermethrin. The adult immersion test (AIT) was used to characterize the susceptibility of tick populations (45 field populations) to synthetic acaricides: deltamethrin, amitraz and chlorfenvinphos. The larval packet test (LPT) was used to determine the LC50 values for thymol (25 tick populations) and carvacrol (20 tick populations). The susceptible strain Porto Alegre (POA) was used as a reference for calculating the resistance ratio (RR). Subsequently, larval immersion tests (LIT) were performed with combinations of cypermethrin with thymol or carvacrol to assess a synergistic effect. In the AIT, deltamethrin showed efficacy > 90% in one (2.2%) population tested (mean: 12.1 and 11.1 for populations 1-25 and 26-40, respectively), whereas amitraz and chlorfenvinphos showed efficacy > 90% for two (4.4%) populations (mean: 61.3 and 47.3 for populations 1-25 and 26-40, respectively) and eight (17.7%) populations (mean: 69.7 and 59.7 for populations 1-25 and 26-40, respectively). In the LPT, the LC50 values for thymol and carvacrol varied from 0.67 to 2.12 mg/mL and 0.55-3.21 mg/mL, with an average LC50 for populations of 1.49 and 1.75 mg/mL, respectively. For thymol, no resistance was observed in any of the populations, values of RR50 > 1.5. There was no correlation between the LC50 values for thymol and the efficacy of the chemical acaricides tested. Regarding carvacrol, for only one tick population had the value of RR50 > 1.5, indicating an incipient resistance. No correlation was observed between the LC50 values for carvacrol and the efficacy of tested acaricides. The combination of thymol and carvacrol with cypermethrin showed a synergistic effect in the resistant population (Jaguar - thymol 4.19 and carvacrol 3.67), and no synergistic interaction were showed in the susceptible population. Answering the questions we conclude that: 1 - The comparison between the LC50 values for thymol and carvacrol in field populations and the susceptible strain POA suggests the absence of cross-resistance (ticks and terpenes), and the differences between the LC50 values for thymol and carvacrol in the different R. microplus populations are inherent to the characteristics of each population tested; 2 - the combination of thymol or carvacrol with cypermethrin showed a synergistic effect with different activity according to the population of ticks.

[Liver and serum glutathione concentration and liver hydrogen peroxide in rats subchronically intoxicated with chlorfenvinphos--organophosphate insecticide]. / Stezenie glutationu w watrobie i w surowicy krwi oraz nadtlenku wodoru w watrobie szczurów w podostrym zatruciu chlorfenwinfosem--insektycydem fosforoorganicznym.

BACKGROUND: Toxicity of organophosphate insecticides is mainly due to the inhibition of acetylcholinesterase (AChE). However organophosphate insecticides in acute as well as in chronic and subchronic intoxication may lead to oxidative stress causing enhancement of lipid peroxidation and changing the activities of antioxidative enzymes and concentration of non-enzymatic antioxidant. For this reason the aim of the work was to estimate glutathione and hydrogen peroxide levels in the liver, as well as the concentration of total glutathione in serum of rats in subchronic intoxication with chlorfenvinphos. MATERIALS AND METHODS: The animals received chlorfenvinphos, intragastrically with use of a stomach tube, at a one daily dose of 0.3 mg/kg/day for 14 or 28 days. For biochemical determinations BIOXYTECH GSH-400 and BIOXYTECH H2O2-560 Assay kit, OXIS International, Inc., Portland, U.S.A. (reduced glutathione and hydrogen peroxide), and Glutathione Assay Kit, Cayman Chemical Company, U.S.A. (determination of serum total glutathione level) were used. RESULTS: Chlorfenvinphos administration resulted in a decreased level of reduced glutathione in liver accompanied by an increase in liver hydrogen peroxide and serum total glutathione concentrations. The observed changes were more pronounced after 28 days of intoxication. CONCLUSIONS: The common use of organophosphate insecticides results in the environmental pollution, therefore, the decreased liver glutathione level is an additional risk factor for people treated with different medicine (e.g., paracetamol).

Assessment of acetylcholinesterase activity in Clarias gariepinus as a biomarker of organophosphate and carbamate exposure.

The objective of this study was to investigate the response of acetylcholinesterase (AChE) activities in Clarias gariepinus in response to Organophosphates (Ops) and carbamate exposure. The AChE activities were determined in plasma, and eye and brain homogenates of unexposed and exposed fish using Ellman's method and 5,5'-dithiobis-2-nitrobenzoic acid (DTNB) chromophore. The baseline AChE activities in plasma, eyes and brain tissues in unexposed fish were comparable between males and females (P > 0.05). Concentrations of pesticides that inhibited 50% (IC(50)) of AChE activities in brain homogenates following in vitro exposures were 0.003, 0.03, 0.15, 190, 0.2, 0.003 and 0.002 microM for carbaryl, chlorfenvinphos, diazinon, dimethoate, fenitrothion, pirimiphosmethyl and profenofos, respectively. The in vivo dose-effect relationships were assessed using chlorfenvinphos and carbaryl at different concentrations that ranged from 0.0003 to 0.06 microM and 0.0005 to 0.05 microM, respectively. Acetylcholinesterase activities were comparable in plasma, and eye and brain homogenates from control and carbaryl-exposed fish. Following exposure of fish to chlorfenvinphos at concentrations above 0.03 microM, a significant inhibition of AChE activities in plasma (84%) and eye homogenate (50%) was observed. The AChE activities in brain homogenate were comparable between chlorfenvinphos-exposed fish and controls. Because carbaryl cause reversible inhibition of AChE activities was found to be more potent than chlorfenvinphos that cause irreversible inhibition following in vitro exposure. Contrary, carbaryl was less potent than chlorfenvinphos after in vivo exposure possibly due to more rapid biotransformation of carbaryl than chlorfenvinphos. Findings from this study have demonstrated that inhibition of AChE activity in C. gariepinus is a useful biomarker in assessing aquatic environment contaminated by anticholinesterases.

Effect of processing on 14C-chlorfenvinphos residues in maize oil and bioavailability of its cake residues on rats.

Maize seeds obtained from 14C-chlorfenvinphos treated plants contained 0.12% of the applied dose. The insecticide residues in crude oil, methanol and cake amounted to 10%, 6% and 69%, respectively of original residues inside the seeds. The 14C-activity in the crude oil could be a gradually reduced by the refining processes. The alkali treatment and bleaching steps are the most effective steps in these processes. The refined oil contained small amount of the 14C-residues originally present. The major residues in processed oil contain the parent compound, in addition to five metabolites of the insecticide. When rats fed the extracted seeds (cake), the bound residues were found to be considerably bioavailability. After feeding rats for five days with the cake, a substantial amount of 14C-residues was eliminated in the urine (59.5%), while about 20% excreted in the feces. About 15% of the radioactive residues were distributed among various organs.

Combined toxicities of binary mixtures of alachlor, chlorfenvinphos, diuron and isoproturon.

Pesticides are the chemicals of increased concern regarding their adverse environmental effects. In particular, the reports on their joint toxicity effects are scarce in the literature. Therefore, this paper describes the experiments on toxicities of four pesticides: alachlor, chlorfenvinphos, diuron, and isoproturon, toward Vibrio fischeri. In particular, the joint toxicity effects for all possible binary combinations of the pesticides were analyzed. The analysis included the application of concentration addition and independent action models at two toxicity levels: EC10 and EC50. The analysis revealed additive behavior between all pesticide pairs. The only exception was isoproturon and chlorfenvinphos whose combination resulted in synergistic toxic activity. The original form of the logistic function was given preference over the linearized form in describing the response-dose relationships of investigated pesticides.