Pesticides organophosphorus insecticides

Environmental Defence recently released Toxic Nation A Report on Pollution in Canadians (Environmental Defence 2005). Samples were collected from 11 people for the presence of 88 chemicals, including heavy metals, PBDEs, PCBs, perfluorinated chemicals, organochlorine pesticides, organophosphorus-insecticide metabolites, and VOCs. The study objectives included determining whether pollutants were present at measurable concentrations in Canadians, identifying chemicals of concern, and creating public awareness of methods for avoiding exposure. 

The reagent sequence is specific for endosulfan and phosphamidon. Other insecticides, e.g. organochlorine insecticides, such as endrin, aldrin, dieldrin, DDT and BHC, organophosphorus insecticides, such as malathion, parathion, dimethoate, quinalphos, phorate and fenitrothion, or carbamate insecticides, such as baygon, car-baryl and carbofuran do not react. Neither is there interference from amino acids, peptides or proteins which might be extracted from the biological material together with the pesticides. 

Organophosphorus insecticides, 19 47 Organophosphorus monomers, 11 496 Organophosphorus pesticide analysis of water, 26 44... 

Snyder et al. [20] have compared supercritical fluid extraction with classical sonication and Soxhlet extraction for the extraction of selected pesticides from soils. Samples extracted with supercritical carbon dioxide modified with 3% methanol at 350atm and 50°C gave a =85% recovery of organochlorine insecticides including Dichlorvos, Endrin, Endrin aldehyde, p,p -DDT mirex and decachlorobiphenyl (and organophosphorus insecticides). 

Studies were initiated at Iowa State University in 1977 to determine if pesticides would be contained and degraded when deposited in water/soil systems. Although the addition of known amounts of the selected pesticides was controlled, the physical environment was not temperature, humidity, wind speed, etc. were normal for the climate of Central Iowa. Four herbicides and two insecticides were chosen on the basis of three factors. Firstly, they represented six different families of pesticides. The four herbicides, alachlor, atrazine, trifluralin, and 2,4-D ester, represent the acetanilides, triazines, dinitroanilines, and phenoxy acid herbicides, respectively. The two insecticides, carbaryl and para-thion, represent the carbamate and organophosphorus insecticides, respectively. Secondly, the pesticides were chosen on the basis of current and projected use in Iowa Q) and the Midwest. Thirdly, the chosen pesticides were ones for which analytical methodology was available. 

Mihara K, Isobe N, Ohkawa H, et al. 1981. Effects of organophosphorus insecticides on mitochondrial and microsomal functions in the liver of rat with special emphasis on fenitrothion. Journal of Pesticide Science 6(3) 307-316. 

Wan Mt, Szeto S, Price P. 1994. Organophosphorus insecticide residues in farm ditches of the lower Fraser Valley of British Columbia. J Environ Science and Health Part B, Pesticides Foods Contaminants and Agricultural Waste, 29(5) 917-949. 

Organophosphorus insecticides are not considered to be persistent pesticides because they are relatively unstable and break down in the environment. As a class they are considered to have a small impact on the environment in spite of their acute effects on organisms. 

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... 

Another organophosphorus insecticide, Bayrusil (XIII) becomes fluorescent upon heat treatment but the fluorescence yield is less than with coumaphos (around 0.01 yg/spot) (4 4). This pesticide has also been analysed in foodstuffs at the 0.02 ppm level (46 ). ... 

The increased use of derivatisation reactions is evident from the gradual increase in the number of publications dealing with the subject. Figure 1 shows the yearly variation in numbers of publications dealing with derivatisation in pesticide analysis over the period 1963 to 1978. While the interest in derivatisation techniques in organophosphorus insecticide analysis has remained fairly constant and a low level of activity, the OC insecticides underwent an increased period of attention from 1968-1972 which has stablized over the last few years. It is in the insecticidal carbamate and herbicide areas that an overall steady increase in the use of derivatisation reactions for quantitative and con-... 

Henry s law constant is an important property in understanding environmental fate of substances. Henry s law constant for a set of organophosphorus insecticides has been collected from The Pesticide Manual (Tomlin, 2000) and is reported in Table 4.5. 

Until now, many substances including pesticides, extracts of plants, and microbial metabolites have been bioassayed to find inhibitory activity on AF production. Organophosphorus insecticides with cholinesterase inhibitory activity, such as dichlorvos (116 in Figure 26), can inhibit AF production by inhibiting the esterase... 

Of the 750 million pounds of pesticides used in 1964, insecticides accounted for nearly half, with herbicides and fungicides comprising most of the balance (23). The markets for fungicides and chlorinated hydrocarbon insecticides have apparently reached a peak while the markets for organophosphorus insecticides and herbicides are increasing. It is predicted that the domestic use of herbicides will far surpass that of insecticides within a few years. 

The first of the organophosphorus insecticides to gain widespread use was parathion which is still an important commercial pesticide. This compound (Figure 9) is converted to the S-ethyl isomer by heating whereas paraoxon, a more toxic compound, is formed by enzymic action in plants. In animals, the additional products, p-nitrophenol and p-amino-phenol, are also formed. At present, little information appears to be available regarding the decomposition products of parathion in soils. 

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