Diazinon selectivity

Forgash, A.J. and Rily, R.C., Mechanisms of resistance in diazinon-selected multi-resistant Musca domestica, /. Econ. EntomoL, 55, 544,1962. 

The organophosphorons insecticides dimethoate and diazinon are mnch more toxic to insects (e.g., housefly) than they are to the rat or other mammals. A major factor responsible for this is rapid detoxication of the active oxon forms of these insecticides by A-esterases of mammals. Insects in general appear to have no A-esterase activity or, at best, low A-esterase activity (some earlier stndies confnsed A-esterase activity with B-esterase activity) (Walker 1994b). Diazinon also shows marked selectivity between birds and mammals, which has been explained on the gronnds of rapid detoxication by A-esterase in mammals, an activity that is absent from the blood of most species of birds (see Section 23.23). The related OP insecticides pirimiphos methyl and pirimiphos ethyl show similar selectivity between birds and mammals. Pyrethroid insecticides are highly selective between insects and mammals, and this has been attributed to faster metabolic detoxication by mammals and greater sensitivity of target (Na+ channel) in insects. 

Although the inhibition-based biosensors are sensitive, they are poor in selectivity and are rather slow and tedious since the analysis involves multiple steps of reaction such as measuring initial enzyme activity, incubation with inhibitor, measurement of residual activity, and regeneration and washing. Biosensors based on direct pesticide hydrolysis are more straightforward. The OPH hydrolyzes ester in a number of organophospho-rus pesticides (OPPs) and insecticides (e.g. paraoxon, parathion, coumaphos, diazinon) and chemical warfare agents (e.g. sarin) [53], For example, OP parathion hydrolyzes by the OPH to form p-nitrophenol, which can be measured by anodic oxidation. Rainina... 

Table 16.8 Sublethal Effects of Diazinon in Selected Mammals... 

Lopez-Avila et al. [36] used a stable isotope dilution gas chromatography-mass spectrometric technique to determine down to O.lppb of pentachlorophenol (also Atrazine, Diazinon and lindane) in soil. Soil samples are extracted with acetone and hexane. Analysis is performed by high-resolution gas chromatography-mass spectrometry with mass spectrometer operated in the selected ion monitoring mode. Accuracy greater than 86% and a precision better than 8% were demonstrated by use of spiked samples. 

The supercritical fluid chromatographic procedure [20] described in section 9.1.1.5 for the determination of organochlorine insecticides in soils has also been applied to river sediments. Snyder et al. [20] compared supercritical fluid extraction with classical sonication and Soxhlet extraction for selected organochlorine insecticides. Samples of sediments extracted with supercritical carbon dioxide modified with 3% methanol at 350atm and 50°C gave =85% recovery of organochlorine insecticides including Dichlorvos, Diazinon, Endrin, Endrin aldehyde, decachlorobiphenyl, p,p -DDT and Mirex. 

Snyder et al. [94] compared supercritical extraction with classical sonication and Soxhlet extraction for the extraction of selected organophosphorus insecticides from soil. Samples extracted with supercritical carbon dioxide modified with 3% methanol at 350atm and 50°C gave a =85% recovery of Diazinon (diethyl-2-isopropyl-6-methyl-4-pyrimidinyl phosphorothiodate or 0,0 diethyl-0-(2-isopropyl-6-methyl-4-pyrimidyl) phosphorothioate). Ronnel (or Fenchlorphos) 0,0-dimethyl-0-2,4,5 trichlorophenol phosphorothiodate), Parathion ethyl (diethyl-p-nitrophenyl (phosphorothioate), Tetrachlorovinphos (trans,-2-chloro-l-(2,4,5 trichlorophenyl) vinyl (chlorophenyl-O-methylphenyl phosphorothioate) and Methiadathion. Supercritical fluid extraction with methanol modified carbon dioxide has been applied to the determination of organophosphorus insecticides in soil [260]. 

These experts collectively have knowledge of diazinon s physical and chemical properties, toxicokinetics, key health end points, mechanisms of action, human and animal exposure, and quantification of risk to humans. All reviewers were selected in conformity with the conditions for peer review specified in Section 104(i)(13) of the Comprehensive Environmental Response, Compensation, and Liability Act, as amended. 

Exposure Registries. No exposure registries for diazinon were located. This substance is not currently one of the compounds for which a subregistry has been established in the National Exposure Registry. The substance will be considered in the future when chemical selection is made for subregistries to be established. The information that is amassed in the National Exposure Registry facilitates the epidemiological research needed to assess adverse health outcomes that may be related to exposure to this substance. 

Control of cattle ticks has followed a similar transition from broad spectrum organophosphates to more selective agents with novel mode of action. In 1956 diazinon (81) was introduced into Australia as the first organophosphate for tick control. Evidence of OP resistance was first detected in 1963 and in 1966 chlordimeform (84) was demonstrated to control the OP-resistant strains. 

Sometimes it is necessary to use different substrates, cofactors and mediators in order to increase the sensitivity. Due to the irreversible nature of many analyte-enzyme interactions, sensing elements must either be reactivated or should be disposable elements. An example is the determination of diazinon and dichlorvos that uses tyrosinase immobilized on screen printed electrodes, and a redox mediator (l,2-naphtaquinone-4-sulfonate) (Everett and Rechnitz, 1998). For other systems a further drawback is the lack of selectivity of some of the enzymes involved. 

Keizer, J., G. D Agostino, R. Nagel, T. Volpe, P. Gnemi and L. Vittozzi. Enzymological differences of AChE and diazinon hepatic metabolism correlation of in vitro data with the selective toxicity of diazinon to fish species. Sci. Total Environ. 171 213—220, 1995. 

The observed concentrations are compared with the model predictions to establish how well the model can simulate the actual situation. Prior to the initiation of such an experiment (5 lysimeter columns 60 cm ID by 200 cm height), a small-scale experiment (3 columns 4.8 cm ID by 50 cm height) was performed to establish breakthrough volumes of the test chemicals, whether or not the selection of the test chemicals was appropriate, and to determine if the analytical methodologies were adequate. The purpose of this paper is to summarize the results of the small-scale experiment. The six test chemicals selected for investigation were dicamba, 2,4-D, atrazine, diazinon, pentachlorophenol, and lindane. Their physico-chemical properties are presented in Table I. Dicamba and... 

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