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PubMed2005

Changes in salmonid communities associated with pesticide runoff events.

Two agricultural runoff events involving the pesticide azinphos-methyl occurred in July 2002 on the Wilmot River, Prince Edward Island, Canada, resulting in the death of thousands of fish. The fish communities from three sites on this river had been sampled in 2001, permitting comparisons of brook trout (Salvelinus fontinalis) and rainbow trout (Oncorhynchus mykiss) populations before and after the events. Samples taken immediately after the runoff events suggested that brook trout suffered higher mortality than rainbow trout. Young-of-the-year fish were more affected than older age classes for both species. Sampling in 2003, a year after the pesticide runoff events, revealed salmonid communities that were still skewed towards rainbow trout, and a decrease in the 1+ age class density (2002's young of the year) at affected sites. These results suggest a differential effect of the pesticide azinphos-methyl on salmonid species and age classes under natural conditions, and a subsequent change in population and community structure. The possibility of these pesticide runoff events selecting for rainbow trout, an exotic species, is a consideration in management of agriculturally impacted rivers.

Animals↗
PubMed1996

Interaction of ethylazinphos with the physical organization of model and native membranes.

The interaction of ethylazinphos with the physical organization of model and native membranes was investigated by means of fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene (DPH) and of its propionic acid derivative (DPH-PA). Ethylazinphos shifts the phase transition midpoint to lower temperature values and broadens the phase transition profile of bilayers reconstituted with dimyristoyl-, dipalmitoyl- and distearoylphosphatidylcholines (DMPC, DPPC, DSPC), as detected by DPH and DPH-PA. Additionally, both probes detect significant effects of ethylazinphos in the fluid phase of the above lipid bilayers. The insecticide perturbations are more pronounced in bilayers of short-chain lipids, e.g., DMPC, in correlation with the higher partition in these membranes. On the other hand, the insecticide increases to some extent the ordering promoted by cholesterol in the fluid phase of DMPC, but high cholesterol concentrations (> or = 30 mol%) almost prevent insecticide interaction, as revealed by DPH and DPH-PA. In agreement with the results in models of synthetic lipids, the increase of intrinsic cholesterol in fluid native membranes depresses the partition values of ethylazinphos and consequently its effects.

Azinphosmethyl↗
PubMed1987

Metabolic activation of the pesticide azinphos-methyl by perfused mouse livers.

Perfusion of mouse livers in situ with the phosphorodithioate pesticide azinphos-methyl (O,O-dimethyl S-[4-oxo-1,2,3-benzotriazin-3(4H)-ylmethyl] phosphorodithioate; Guthion) resulted in the appearance of the cholinesterase inhibitor azinphos-methyl oxon in effluent perfusate. Since mouse whole blood did not have the capacity to detoxify this toxic oxon rapidly enough to prevent its passage to extrahepatic tissues in vivo, the liver is likely a major source of azinphos-methyl oxon in the mouse following exposure to azinphos-methyl. Alterations in perfusate flow rates in situ had little effect on the hepatic disposition of azinphos-methyl. Conversely, significant increases in the free fraction of azinphos-methyl in perfusate led to marked changes in hepatic distribution and biotransformation of this pesticide. Phenobarbital pretreatment of mice induced hepatic cytochrome P-450 content, as well as microsomal activation of azinphos-methyl in vitro, yet antagonized the acute toxicity of this pesticide in vivo. Interestingly, perfused livers from phenobarbital-pretreated mice produced less azinphos-methyl oxon than perfused livers from saline-pretreated mice, thereby accounting for the antagonism of the acute toxicity of azinphos-methyl afforded by phenobarbital pretreatment. The mechanism of this phenobarbital-dependent decrease in appearance of azinphos-methyl oxon in effluent perfusate is unclear. However, it must be emphasized that the hepatic biotransformation of azinphos-methyl is complex, involving several sequential and simultaneous pathways, all of which could be affected by phenobarbital. The metabolic profile observed in effluent perfusate is the net result of all these pathways operating in the intact liver.

Animals↗
PubMed1988

The role of glutathione in the detoxification of the insecticides methyl parathion and azinphos-methyl in the mouse.

The dimethyl-substituted organothiophosphate insecticides methyl parathion and azinphos-methyl are thought to undergo glutathione-mediated detoxification in mammals. In the present study, depletion of hepatic glutathione in the mouse by pretreatment with diethyl maleate potentiated the acute toxicities of methyl parathion and azinphos-methyl, whereas depletion of hepatic glutathione by pretreatment with buthionine sulfoximine did not. Furthermore incubation of 50 microM methyl parathion with mouse hepatic microsomes for 5 min in the presence of 1 mM diethyl maleate led to significantly greater (p less than 0.05) production of methyl paraoxon, compared to incubations in the absence of diethyl maleate. Conversely, 1 mM diethyl maleate had no effect on metabolic activation of azinphos-methyl by mouse hepatic microsomes, while 10 mM inhibited slightly production of azinphos-methyl oxon from azinphos-methyl. These results suggest normal levels of hepatic glutathione are not required for detoxification of methyl parathion or azinphos-methyl in the mouse. Moreover the potentiation of the acute toxicity of methyl parathion following diethyl maleate pretreatment could result, at least in part, from enhanced production of methyl paraoxon. However, diethyl maleate likely acts through another mechanism(s) as well since it did not enhance the metabolic activation of azinphos-methyl in vitro. These data raise serious doubts about the participation of glutathione in the detoxification of methyl parathion and azinphos-methyl in vivo in the mouse.

Animals↗
PubMed1983

In vivo induction of sister-chromatid exchange in Umbra limi by the insecticides endrin, chlordane, diazinon and guthion.

Central mudminnows, Umbra limi, were exposed to the insecticides endrin, chlordane, diazinon and guthion at concentrations of 5.4 X 10(-12) M to 5.4 X 10(-9) M in the aquaria water. Endrin, chlordane and diazinon caused significant increase in the frequencies of SCE. The results of these tests in part are in contrast to previous work which did not find endrin to be mutagenic. Our results suggest that the in vivo SCE test is an efficacious method of detecting mutagenic pesticides in water.

Animals↗
PubMed1994

Genotoxicity assay of five pesticides and their mixtures in Saccharomyces cerevisiae D7.

Four organophosphorus pesticides (azinphos-methyl, diazinone, dimethoate, and pirimiphos-methyl), and one carbamate (benomyl) were tested for cytotoxicity, reverse mutation and gene conversion in Saccharomyces cerevisiae D7, with and without the S9 metabolic system. Furthermore, two mixtures of the above compounds, namely benomyl + pirimiphos-methyl (6/1 ratio) and dimethoate + diazinone + azinphos-methyl (10/4/6 ratio) were tested in the same experimental model. Azinphos-methyl, benomyl, and pirimiphos-methyl alone did not induce any genotoxic effect, whereas azinphos-methyl and diazinone were active in inducing reversion and gene conversion. The benomyl + pirimiphos-methyl mixture did not show any genotoxic activity. The dimethoate + diazinone + azimphos-methyl mixture was genotoxic, although an antagonistic effect between the components was observed. The addition of S9 post-mitochondrial liver fraction decreased the activity of both single and mixed genotoxic agents.

Animals↗
PubMed1982

Sister-chromatid exchanges and cell-cycle delay in Chinese hamster V79 cells treated with 9 organophosphorus compounds (8 pesticides and 1 defoliant).

Significant increase of sister-chromatid exchanges (SCE) in V79 cells treated with 2 organophosphorus pesticides (OPP), fenthion and oxydemeton-methyl, was observed. The other 7 compounds (6 OPP and 1 defoliant) namely, amaze, azinphos-methyl, bolstar, DEF-defoliant, fensulfothion, monitor and nemacur caused no increase of SCE frequencies at the doses tested. All the compounds except fensulfothion and oxydemeton-methyl induced cell-cycle delay in varying degrees. Cell-cycle delay caused by an OPP was found to be dose-dependent. Based on these data as well as others reported, it would appear that OPP which induce no SCE increase and no or slight cell-cycle delay could be considered as good candidates to substitute the pesticides that have been found to be harmful to the environment.

Animals↗
PubMedDate not supplied

Mixtures of benomyl, pirimiphos-methyl, dimethoate, diazinon and azinphos-methyl affect protein synthesis in HL-60 cells differently.

Dimethoate, azinphos-methyl, diazinon and pirimiphos-methyl, widely used organophosphorous insecticides, and benomyl, a benzimidazole fungicide, induce different cytotoxic effects on the human leukemia cell line HL-60. Among the insecticides tested, only azinphos and diazinon induced a dose-related inhibition of protein synthesis in HL-60 cells at 24 h, at 60 and 40 micrograms/ml medium, respectively. Dimethoate and pirimiphos were not active up to 100 micrograms/ml. Benomyl strongly inhibited protein synthesis at 50 micrograms/ml and the polymerisation of actin to give cytoskeletal microfilaments (F-actin) at 30 micrograms/ml. Mixtures of benomyl-pirimiphos and dimethoate azinphos-diazinon were also investigated. Pirimiphos, when present in equal concentration, antagonized the inhibitory effect of benomyl on protein synthesis at 4 h, but not at 24 h. The effect of the other insecticide mixture on the same parameter was greater than that of the two active components, diazinon and azinphos given singly.

Actins↗
PubMed1995

Long vs. short monitoring intervals for peach harvesters exposed to foliar azinphos-methyl residues.

A dermal monitoring study of peach harvesters exposed to azinphos-methyl (AM) residues was conducted in Sutter County, California. Harvesters were paid by piecework, which allowed characterization of the relationship between dermal exposure (DE) and time or production. Workers wore 2 long-sleeved knit T-shirts for each monitoring interval and also provided a hand residue sample. Dislodgeable foliar residue (DFR) samples were also collected. The highest correlations were found for inner shirts vs. production and DE vs. time worked (r2 = 0.67, P < 0.01). DE was greatest after 2-h exposures and reached equilibrium after 3 h, indicating that exposure estimates from shorter intervals would overestimate exposure.

Agriculture↗
PubMed1991

Elevated esterase activity in resistant tufted apple bud moth, Platynota idaeusalis (Walker) (Lepidoptera: Tortricidae).

1. Esterase activity in the tufted apple bud moth was measured spectrophotometrically by the hydrolysis of alpha-naphthyl acetate. 2. Resistant populations from both laboratory and field exhibited significantly greater esterase activity than did the respective susceptible populations. 3. The resistant laboratory population had significantly higher esterase activity than the resistant field population, suggesting that this field population contained a mixture of resistant and susceptible individuals.

Animals↗
PubMed2004

Different susceptibility of two aquatic vertebrates (Oncorhynchus mykiss and Bufo arenarum) to azinphos methyl and carbaryl.

We studied the effect of two insecticides azinphos methyl and carbaryl on two resident aquatic species (Oncorhynchus mykiss and Bufo arenarum). Juvenile trout and larval stages of toad were used for exposure and recovery assays. O. mykiss was more sensitive to azinphos methyl exposure than B. arenarum larvae, with a mean 96-h LC50 of 0.007 mg/l. Carbaryl is markedly less toxic than the organophosphate and the differences in potency, expressed as LC50, for both species varies only by five-fold. The relationship between cholinesterase (ChE) inhibition and lethality is not straightforward: O. mykiss survives with an almost complete inhibition of the brain enzyme when exposed to azinphos methyl and carbaryl. Their IC50 values are one or two orders of magnitude lower than the corresponding 96-h LC50 value. In B. arenarum larvae, the IC50 values for azinphos methyl and carbaryl are one half and one third of their 96-h LC50s, respectively. The time courses of enzyme inhibition and recovery also points out differences between both types of pesticides and species. Identifying the key features conferring species selectivity can be exploited to minimize the incidence and severity of intoxication of non-target organism. The data presented here highlight the necessity of including several species and endpoint analyses in the pesticide risk evaluations of aquatic ecosystems.

Animals↗
PubMed2005

Mitigation of azinphos-methyl in a vegetated stream: comparison of runoff- and spray-drift.

The effectiveness of aquatic macrophytes in reducing runoff- and spray-drift-induced azinphos-methyl (AZP) input was compared in a vegetated stream. Water, sediment and plant samples were taken at increasing distances from a point of input during a spray-drift event and two runoff (10 and 22 mm/day) events. Peak concentrations of AZP decreased significantly (R2=0.99; p<0.0001; n=5) from 0.24 microg/l to 0.11 microg/l during the 10mm runoff event. No reduction took place during the 22 mm event. AZP concentrations were reduced by 90% following spray-drift input, with peak concentrations decreasing significantly (R2=0.93; p=0.0084; n=5) from 4.3 microg/l to 1.7 microg/l with increasing distance from the point of input. Plant samples taken after the spray-drift event showed increased AZP concentrations in comparison to before the event indicating sorption of the pesticide to the macrophytes. Although peak concentrations of AZP were as effectively mitigated during the 10mm runoff event as during the spray-drift event, predictive modelling revealed that maximum concentrations expected during a worst-case scenario 10mm runoff event (0 days after application) are an order of magnitude lower than what can be expected for a worst-case spray-drift and 22 mm runoff event, suggesting that spray-drift-derived pesticide concentrations are more effectively mitigated than those of runoff.

Azinphosmethyl↗
PubMed2006

Photodegradation of organophosphorus insecticides - investigations of products and their toxicity using gas chromatography-mass spectrometry and AChE-thermal lens spectrometric bioassay.

Four organophosphorus compounds: azinphos-methyl, chlorpyrifos, malathion and malaoxon in aqueous solution were degraded by using a 125 W xenon parabolic lamp. Gas chromatography-mass spectrometry (GC-MS) was used to monitor the disappearance of starting compounds and formation of degradation products as a function of time. AChE-thermal lens spectrometric bioassay was employed to assess the toxicity of photoproducts. The photodegradation kinetics can be described by a first-order degradation curve C=C0e(-kt), resulting in the following half lives: 2.5min for azinphos-methyl, 11.6 min for malathion, 13.3 min for chlorpyrifos and 45.5 min for malaoxon, under given experimental conditions. During the photoprocess several intermediates were identified by GC-MS suggesting the pathway of OP degradation. The oxidation of chlorpyrifos results in the formation of chlorpyrifos-oxon as the main identified photoproduct. In case of malathion and azinphos-methyl the corresponding oxon analogues were not detected. The formation of diethyl (dimethoxy-phosphoryl) succinate in traces was observed during photodegradation of malaoxon and malathion. Several other photoproducts including trimethyl phosphate esters, which are known to be AChE inhibitors and 1,2,3-benzotriazin-4(3H)-one as a member of triazine compounds were identified in photodegraded samples of malathion, malaoxon, and azinphos-methyl. Based on this, two main degradation pathways can be proposed, both result of the (P-S-C) bond cleavage taking place at the side of leaving group. The enhanced inhibition of AChE observed with the TLS bioassay during the initial 30 min of photodegradation in case of all four OPs, confirmed the formation of toxic intermediates. With the continuation of irradiation, the AChE inhibition decreased, indicating that the formed toxic compounds were further degraded to AChE non-inhibiting products. The presented results demonstrate the importance of toxicity monitoring during the degradation of OPs in processes of waste water remediation, before releasing it into the environment.

Acetylcholinesterase↗
PubMed2005

The impact of organophosphate pesticides in orchards on earthworms in the Western Cape, South Africa.

Earthworm population density was measured in and adjacent to an orchard in an agricultural area in the Western Cape, South Africa. Worm densities were very low in orchards (22/m(2)) compared to adjacent uncultivated fields (152/m(2)) at a distance from the orchards. The possible effect of organophosphate pesticides on the earthworms was investigated. Background soil concentrations of chlorpyrifos prior to the start of the spraying season were low (0.2-2.7 microg/kg) but persistent for up to 6 months after the last spraying event, and the pesticide was, as a result of rainfall, transported to nontarget areas by runoff. Background concentrations of azinphos methyl were higher than those of chlorpyrifos (1.6-9.8 microg/kg) but not detectable 2 weeks after a spraying event. Azinphos methyl was mostly transported by wind (spray drift) to adjacent areas. A microcosm study indicated effects of chlorpyrifos on earthworms as determined by measuring biomass change and Cholinesterase inhibition. It is concluded that earthworms were affected detrimentally by the pesticides due to chronic (chlorpyrifos) and intermittent (azinphos methyl) exposure.

Agriculture↗
PubMed2006

A sub-second fast Fourier transform-adsorptive voltammetric technique for the nano-level determination of guthion at a gold microelectrode in flowing solutions.

This research demonstrates the quick guthion monitoring with the help of a sensitive method called fast Fourier transformation continuous cyclic voltammetry (FFTCV). Fortunately, FFTCV illustrates the benefits of precision, determination speed, cost-effectiveness, accuracy and simplicity, in comparison with formerly reported techniques. In particular, this method was applied to a gold microelectrode in flowing solutions to detect the guthion concentration in its formulations. The effects of several parameters were examined regarding the sensitivity of the method. After a series of experiments, the detection limit of the method was found to be equal to 1.27 pg/mL, when the optimum conditions were imposed, which is a scan rate value of 40V/s, an accumulation time of 0.4s, an accumulation potential of 0mV and a pH value of 2. During the measurements performance, the integration range of currents included all the potential scan ranges, even the oxidation and reduction of the Au surface electrode, for the achievement of a sensitive determination. Then, the potential waveform, consisting of the potential steps for cleaning, accumulation and the step for the potential ramp, was applied to an Au disk microelectrode in a continuous way. It is also important to refer to the positive points, presented only by the use of this technique. Firstly, it is no longer necessary to remove the oxygen from the test solution. Furthermore, the quick determination of any such compound in many chromatographic methods is possible. Thirdly, the corresponding detection limit is of nanomolar level.

Azinphosmethyl↗