Dimethoate appears as a white crystalline solid, with a camphor-like odor, white to grayish crystals for technical product. This material is a contact and systemic organophosphate insecticide effective against a broad range of insects and mites when applied on a wide range of crops. It has not been produced in the U.S. since 1982. (EPA, 1998)
... Detoxification pathway ... involves the hydrolysis of carboxyester or carboxyamide linkages in some insecticides by tissue or plasma carboxylesterases (sometimes called aliesterase). Malathion and dimethoate are examples.
After dimethoate was administered to rats, the following compounds were found in urine: 1. dimethoate, 2. dimethoxon, 3. dimethoate carboxylic acid, 4. dimethylphosphorodithioate, 5. dimethyl phosphorothioate, 6. dimethylphosphate, 7. monomethylphosphate, 8. phosphorothioate, 9. formate, and 10. N-methyl 2-glucuronate acetamide.
Oxidative desulfuration of dimethoate to give O-analog took place rapidly in rabbits and rats. Both dimethoate and O-analog underwent subsequent oxidative N-dealkylation coupled with formation of N-hydroxymethyl intermediates.
Dimethoate is a cholinesterase or acetylcholinesterase (AChE) inhibitor. A cholinesterase inhibitor (or 'anticholinesterase') suppresses the action of acetylcholinesterase. Because of its essential function, chemicals that interfere with the action of acetylcholinesterase are potent neurotoxins, causing excessive salivation and eye-watering in low doses, followed by muscle spasms and ultimately death. Nerve gases and many substances used in insecticides have been shown to act by binding a serine in the active site of acetylcholine esterase, inhibiting the enzyme completely. Acetylcholine esterase breaks down the neurotransmitter acetylcholine, which is released at nerve and muscle junctions, in order to allow the muscle or organ to relax. The result of acetylcholine esterase inhibition is that acetylcholine builds up and continues to act so that any nerve impulses are continually transmitted and muscle contractions do not stop. Among the most common acetylcholinesterase inhibitors are phosphorus-based compounds, which are designed to bind to the active site of the enzyme. The structural requirements are a phosphorus atom bearing two lipophilic groups, a leaving group (such as a halide or thiocyanate), and a terminal oxygen.
来源:Toxin and Toxin Target Database (T3DB)
毒理性
致癌性证据
癌症分类：C组可能的人类致癌物
Cancer Classification: Group C Possible Human Carcinogen
Acute exposure to cholinesterase inhibitors can cause a cholinergic crisis characterized by severe nausea/vomiting, salivation, sweating, bradycardia, hypotension, collapse, and convulsions. Increasing muscle weakness is a possibility and may result in death if respiratory muscles are involved. Accumulation of ACh at motor nerves causes overstimulation of nicotinic expression at the neuromuscular junction. When this occurs symptoms such as muscle weakness, fatigue, muscle cramps, fasciculation, and paralysis can be seen. When there is an accumulation of ACh at autonomic ganglia this causes overstimulation of nicotinic expression in the sympathetic system. Symptoms associated with this are hypertension, and hypoglycemia. Overstimulation of nicotinic acetylcholine receptors in the central nervous system, due to accumulation of ACh, results in anxiety, headache, convulsions, ataxia, depression of respiration and circulation, tremor, general weakness, and potentially coma. When there is expression of muscarinic overstimulation due to excess acetylcholine at muscarinic acetylcholine receptors symptoms of visual disturbances, tightness in chest, wheezing due to bronchoconstriction, increased bronchial secretions, increased salivation, lacrimation, sweating, peristalsis, and urination can occur. Certain reproductive effects in fertility, growth, and development for males and females have been linked specifically to organophosphate pesticide exposure. Most of the research on reproductive effects has been conducted on farmers working with pesticides and insecticdes in rural areas. In females menstrual cycle disturbances, longer pregnancies, spontaneous abortions, stillbirths, and some developmental effects in offspring have been linked to organophosphate pesticide exposure. Prenatal exposure has been linked to impaired fetal growth and development. Neurotoxic effects have also been linked to poisoning with OP pesticides causing four neurotoxic effects in humans: cholinergic syndrome, intermediate syndrome, organophosphate-induced delayed polyneuropathy (OPIDP), and chronic organophosphate-induced neuropsychiatric disorder (COPIND). These syndromes result after acute and chronic exposure to OP pesticides.
来源:Toxin and Toxin Target Database (T3DB)
毒理性
暴露途径
这种物质可以通过吸入、皮肤接触和摄入被身体吸收。
The substance can be absorbed into the body by inhalation, through the skin and by ingestion.
来源:ILO-WHO International Chemical Safety Cards (ICSCs)
Qualitatively, metabolism of dimethoate in mammals is essentially identical to that occurring in insects. There are... quantitative differences. In general, dimethoate, is much more rapidly degraded in mammals and eliminated via urine. For example, 87-90% of oral dose given cattle was found in urine after 24 hr, mainly as hydrolysis products.
... Dimethoate rapidly penetrated isolated sections of /mouse/ small intestine, colon, and rectum, with the highest rates of penetration occurring in the colon and rectum. The age of the mice had no significant effects on the extent of penetration. /Initial dose not specified/
... Following aerial spraying with 38% dimethoate animal tissues contained higher concentrations of dimethoate than did soil, water or plants. ... The tissue containing the highest concentrations were brain and intially, lung. ...
The effects of substrate orientation on the mechanism of a phosphotriesterase
作者：Colin J. Jackson、Jian-Wei Liu、Michelle L. Coote、David L. Ollis
DOI：10.1039/b512399b
日期：——
While the underlying chemistry of enzyme-catalyzed reactions may be almost identical, the actual turnover rates of different substrates can vary significantly. This is seen in the turnover rates for the catalyzed hydrolysis of organophosphates by the bacterial phosphotriesterase OpdA. We investigate the variation in turnover rates by examining the hydrolysis of three classes of substrates: phosphotriesters, phosphothionates, and phosphorothiolates. Theoretical calculations were used to analyze the reactivity of these substrates and the energy barriers to their hydrolysis. This information was then compared to information derived from enzyme kinetics and crystallographic studies, providing new insights into the mechanism of this enzyme. We demonstrate that the enzyme catalyzes the hydrolysis of organophosphates through steric constraint of the reactants, and that the equilibrium between productively and unproductively bound substrates makes a significant contribution to the turnover rate of highly reactive substrates. These results highlight the importance of correct orientation of reactants within the active sites of enzymes to enable efficient catalysis.
Rapid TiO 2 /SBA-15 synthesis from ilmenite and use in photocatalytic degradation of dimethoate under simulated solar light
作者：Ge Li、Baodong Wang、Wayne Qiang Xu、Yifan Han、Qi Sun
DOI：10.1016/j.dyepig.2018.03.058
日期：2018.8
activity and good stability during four cycles, with a dimethoatedegradation rate greater than 94%. The byproducts generated during photocatalysis were identified using gas chromatography-mass spectrometry. The photocatalytic degradation of dimethoate followed first-order kinetics. The mechanism of the photocatalytic degradation of dimethoate was investigated.
The invention relates to novel substituted 1,3,5-oxadiazin-2-ones of the formula ##STR1## wherein R.sub.1 and R.sub.4 are each independently of the other C.sub.1 -C.sub.8 alkyl, C.sub.3 -C.sub.6 -cycloalkyl, C.sub.3 -C.sub.4 alkenyl, C.sub.3 -C.sub.4 alkynyl, phenyl, or benzyl; R.sub.2 and R.sub.3 are each independently of the other hydrogen, C.sub.1 -C.sub.4 alkyl, or R.sub.2 and R.sub.3, together with the carbon atom to which they are attached, are C.sub.3 -C.sub.6 cycloalkyl; and n is 0, 1 or 2; to the preparation of these compounds and to compositions containing them for use in pest control, in particular for controlling insects and representatives of the order Acarina that attack plants and animals. In particular, the novel compounds are very effective against plant-destructive sucking and feeding insects.
Estimation of dioxin emission from fires in chemicals
作者：J Vikelsøe、E Johansen
DOI：10.1016/s0045-6535(99)00231-3
日期：2000.1
The formation of the 17 toxic 2,3,7,8-substituted PCDDs and PCDFs during combustion of selected chemicals were measured by high-resolution GC/MS. The 16 chemicals studied were commonly used chlorinated pesticides, industrial chemicals, and PVC. In a series of experiments carried out in a DIN 53,436 furnace, 2.5 g of these compounds were burned at 500 degrees C and 900 degrees C, respectively. The resultant yields ranged from 740 ng ITEQ/g for pentachlorophenol, to below 0.01 ng ITEQ/g for PVC and dichlobenil. The results show that some chemicals generate PCDD/F in very high possibly dangerous - amounts during burning, whereas others generate insignificant amounts. The influence of scale were studied for chlorobenzene and 4-chloro-3-nitro-benzoic acid in additional experiments, carried out in a cone calorimeter burning 20 g substance, and in ISO 9705 room test burning about 50 kg. A good agreement between the results for large and small scale indicated that formation of PCCD/F during a fire may be estimated from laboratory experiments. This suggest laboratory test may be used to screen for chemicals posing a hazard for release of PCDD/F during fires. (C) 1999 Elsevier Science Ltd. All rights reserved.
