Pesticides demeton

Metasystox A trade name for demeton-methyl, C[Pg.257]

Mechanism of action can be an important factor determining selectivity. In the extreme case, one group of organisms has a site of action that is not present in another group. Thus, most of the insecticides that are neurotoxic have very little phytotoxicity indeed, some of them (e.g., the OPs dimethoate, disyston, and demeton-5 -methyl) are good systemic insecticides. Most herbicides that act upon photosynthesis (e.g., triaz-ines and substituted ureas) have very low toxicity to animals (Table 2.7). The resistance of certain strains of insects to insecticides is due to their possessing a mutant form of the site of action, which is insensitive to the pesticide. Examples include certain strains of housefly with knockdown resistance (mutant form of Na+ channel that is insensitive to DDT and pyrethroids) and strains of several species of insects that are resistant to OPs because they have mutant forms of acetylcholinesterase. These... 

Each pesticide used in the USSR had the same history permit, realization that a mistake was made, ban. The only variable in all of these histories was the length of time required to understand that a mistake had been made when the permit was issued. When removing the pesticide from circulation, officials dted several reasons wen/ high toxicity (aldrin, dieldrin, parathion, demeton,... 

The first day after cotton fields in Uzbekistan were treated with the OPPs demeton and DEF, the average daily concentration of these pesticides were tenths of a mg/m3 at a distance of 500-1000 m from the edge of the treated field, i.e. many times higher than levels that are safe for humans. 

World Health Organization Data Sheets on Pesticides No. 60. Demeton. pp 1-12. http //vrvrw. inchem. org/documents/pds/pds/ pest60 e.htm... 

Demeton, or Systox, was one of the most interesting and challenging pesticides studied. Demeton consists of two isomers, Demeton-S and Demeton-0. The vapor pressures of both isomers are reported to be nearly the same. When gas chromatographed, the isomers are completely resolved and easily quantitated separately. 

Air analysis for some of the individual pesticides of this class has been published by NIOSH. These pesticides include mevinphos, TEPP, ronnel, malathion, parathion, EPN, and demeton (NIOSH Methods 2503, 2504, 1450). In general, pesticides in air may be trapped over various filters, such as Chro-mosorb 102, cellulose ester, XAD-2, PTFE membrane (1 pm), or a glass fiber filter. The analyte(s) are extracted from the filter or the sorbent tube with toluene or any other suitable organic solvent. The extract is analyzed by GC (using a NPD or FPD) or by GC/MS. The column conditions and the characteristic ions for compound identifications are presented in the preceding section. Desorption efficiency of the solvent should be determined before the analysis by spiking a known amount of the analyte into the sorbent tube or filter and then measuring the spike recovery. 

Fig. 15.5 Comparison of gas chromatogram obtained with (i) a phosphorus detector and (ii) an electron capture detector (a) an extract equivalent to IL of Thames water and (b) the same extract fortified with pesticides. Peaks correspond to 5ng of each compound 1, Demeton-S-methyl ...

Gas chromatography has been used [183] to determine the following at organophosphorus insecticides at the microgram per litre level in water and waste water samples Azinphos-methyl, Demeton-O, Demeton-S, Diazinon, Disulfoton, Malathion, Parathion-methyl and Parathion-ethyl. This method is claimed to offer several analytical alternatives, dependent on the analyst s assessment of the nature and extent of interferences and the complexity of the pesticide mixtures found. Specifically, the procedure uses a mixture of 15% v/v methylene chloride in hexane to extract... 

The following OPPs were taken off the U.S. National Pesticide Survey list due to significant losses when stored at 4°C parathion-ethyl, parathion-methyl, azinphos-methyl, fenitrothion, demeton, fenthion, diazinon, fonofos, malathion, disulfoton, terbufos, phosmet, and ethion. ... 

Of the 19 pesticides grouped in Table II, all were negative in five Phase I bioassays and the Phase 2 bioassays performed. These compounds included insecticides (I), fungicides (F), and herbicides (H). Malath ion, parathion, pentachloronitrobenzene (PCNB), and phorate were also negative for heritable chromosomal effects in the mouse dominant lethal test. The six compounds grouped in Table III that were positive in three or more bioassays were acephate, captan, demeton, folpet, monocrotophos, and trichlorfon. Positive results were seen for demeton in all in vitro tests in Phase 1 and Phase 2. Folpet and captan were positive in all Phase 1 and all Phase 2 in vitro assays except the test for unscheduled DNA synthesis in WI-38 cells. Trichlorfon was positive in all Phase 1 and Phase 2 in vitro tests, with the exclusion of relative toxicity tests with E coli and subtiI is. 

The second group, persistent pesticides, includes certain triazine herbicide derivatives, 2,4-dichlorophenoxycarbonic acids, and others (Buslovich 1986, Popovich and Burkatskaya 1986). Moderately persistent pesticides, the third class, include some systemic organophosphorus pesticides (such as demeton, demeton-methyl, Ekatin, and dimethoate), many synthetic pyrethroids, carbamates, and others. Examples of the fourth division, slightly persistent pesticides, are certain contact organophosphorus chemicals like parathion, methyl-para-thion, and others (Kagan 1977, 1981). 

The organophosphorus pesticides oxydemeton-methyl, trichlorfon, dimethoate, dichlorvos, demeton-j-methyl, fenitrooxon, and fenamiphos (and two metabolites)... 

---