Pesticides pyrethroids

T. Cairns and J. Sherma, eds.. Comprehensive Analytical Profiles of Important Pesticides, CRC Press, Boca Raton, Fla., 1992, 304 pp. From the series ModemMethods for Pesticide Analysis, provides detailed information on properties and analytical methodology for nine prominent pesticides, pyrethroids, and fumigants in food. Includes formulations and uses, chemical and physical properties, toxicity data, and tolerances on various foods and feeds. Analytical information may be given in enough detail for methods to be carried out without having to consult additional Hterature sources. 

Pesticide) Pyrethroids European continent Soil and water - Total pesticide use - Spatial distribution of crops - Crop types (cereal, maize, oilseeds, citrus, etc.) - Runoff and soil moisture - Fate and transport parameters [52]... 

POM particulate organic matter >380 pesticides (pyrethroids), polycyclic aromatic hyciocarbons, phthalates and organophosphates having high boiling points (e.g., TCP, DEHP)... 

These chemorational techniques have generated great interest in, and high expectations for, the acceleration of development of innovative pesticides. However, many purportedly successful appHcations of QSAR procedures have reHed on the quaHtative insights traditionally associated with art-based pesticide development programs. Retrospective QSAR analyses have, however, been helpful in identifying the best compounds for specific uses (17). Chemorational techniques have also found some appHcations in the development of pesticides from natural product lead compounds, the best known examples being the synthetic pyrethroid insecticides (19) modeled on the plant natural product, pyrethmm. 

Carboyylic acid ester hydrolysis is frequendy observed as the initial reaction for pesticides with ester bonds, such as 2,4-D esters, pyrethroids, and DCPA (dacthal) (8) (eq. 11) (16). 

Since 1945 the use of synthetic pesticides in the United States has grown 33-fold. The amounts of herbicides, insecticides, and fungicides used have changed with time due, in large part, to changes in agricultural practices and cosmetic standards (14, 15). At the same time, the toxicity and biological effectiveness of these pesticides have increased at least 10-fold (15). For example, in 1945 DDT was applied at a rate of about 2 kg/ha. With the more potent insecticides available now, similar effective insect control is achieved with pyrethroids and aldicarb applied at 0.1 kg/ha and 0.05 kg/ha, respectively. 

Amweg EL, Weston DP, Ureda NM (2005) Use and toxicity of pyrethroid pesticides in the Central Valley, California, USA. Environ Toxicol Chem 24(4) 966-972... 

Weston DP, Holmes RW, Lydy MJ (2009) Residential runoff as a source of pyrethroid pesticides to urban creeks. Environ Pollut 157(l) 287-294... 

In a study of 135 workers in the ehemical industry who handle methyl parathion, the methyl parathion concentration in plasma, the 4-nitrophenol concentration in urine, and the cholinesterase and acetylcholinesterase activities were determined to assess the pesticide burden in such workers (Leng and Lewalter 1999). The mean concentration of methyl parathion in the plasma of the workers was 233 pg/L no clinical symptoms were reported by the workers. In an additional group of 19 workers handling methyl parathion, who were also exposed to the pyrethroid cyfluthrin, the mean concentrations of methyl parathion in plasma were 269 and 241 pg/L (for groups without and with clinical S5miptoms, respectively), and 7 of the workers exhibited skin paraesthesia, while none of the 427 workers exposed only to the pyrethroid experienced the symptom (Leng and Lewalter 1999). 

Many pesticides are not as novel as they may seem. Some, such as the pyre-throid and neonicotinoid insecticides, are modeled on natural insecticides. Synthetic pyrethroids are related to the natural pyrethrins (see Chapter 12), whereas the neo-nicotinoids share structural features with nicotine. In both cases, the synthetic compounds have the same mode of action as the natural products they resemble. Also, the synthetic pyrethroids are subject to similar mechanisms of metabolic detoxication as natural pyrethrins (Chapter 12). More widely, many detoxication mechanisms are relatively nonspecific, operating against a wide range of compounds that... 

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... 

The other major mechanism of pyrethroid resistance found in some field strains of Heliothis virescens was enhanced detoxication due to a high rate of oxidative detoxication, mediated by a form of cytochrome P450 (McCaffery 1998). Some strains, such as PEG 87, which was subjected to a high level of field and laboratory selection, possessed both mechanisms. Other example of pyrethroid resistance due to enhanced detoxication may be found in the literature on pesticides. 

Jaensson, A., Scott, A.P., and Moore, A. et al. (2007). Effects of a pyrethroid pesticide on endocrine responses to female odours and reproductive behaviour in male parr of brown trout (Salmo trutta L.). Aquatic Toxicology 81, 1-9. 

Pilling, E.D., Bromley-ChaUenor, K.A.C., and Walker, C.H. et al. (1995). Mechanism of synergism between the pyrethroid insecticide lambda cyhalothrin and the imidazole fungicide prochloraz in the honeybee. Pesticide Biochemistry and Physiology 51, 1-11. 

The use of SPE with porous materials such as alumina, diatomaceous earth, Horisil and silica for the cleanup of fat-soluble organochlorine pesticides in fatty foods such as meat, flsh, shellfish, milk and vegetable oils has been well documented. The choice of elution solvents is critical because relatively small amounts of lipid in the final extract can cause rapid deterioration of GC capillary columns and also contaminate the gas chromatograph. A number of workers have used a porous material in tandem with Cig to effect an improved cleanup.Di Mucchio employed a multicartridge system comprising Extrelut, silica and Cig to extract organophosphorus pesticides from oils and fatty extracts. Relatively few literature applications include the pyrethroids, but Ramesh and Balasubramanian reported a simple carbon-based SPE method for the analysis of pyrethroids in vegetable oil. 

For an individual pesticide (e.g., carbendazim) or a limited class of pesticides (e.g., carbamates, benzoylphenylureas, pyrethroids ), it may be possible to optimize the SPE conditions so that the pesticide(s) are selectively retained on the cartridge. A wash step can be introduced to elute the matrix selectively, thus producing an extremely clean extract. For example, when cleaning up sample extracts for carbendazim analysis, a cation-exchange (SCX) cartridge may be used and the pH carefully controlled to retain the carbendazim firmly, whilst the co-extractives are washed to waste. The carbendazim residues can then be eluted from the column by adjusting the pH. 

Feo ML, Eljarrat E, Ginebreda A et al (2010) Presence of pyrethroid pesticides in water and sediments of Ebro River Delta. J Hydrol doi 10.1016/j.jhydrol.2010.08.012... 

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