Pesticides organophosphates

Suggest an enzyme electrode-based procedure for detecting organophosphate pesticides. 

Mice that were exposed dermally to residues of methyl parathion in emulsifiable concentrate on foliage, and were muzzled to prevent oral intake, developed inhibition of plasma cholinesterase and erythrocyte cholinesterase after two 10-hour exposures (Skinner and Kilgore 1982b). For the organophosphate pesticides tested in this study, cholinergic signs generally were seen in mice with cholinesterase inhibition >50% results for this end point were not broken down by pesticide. 

The lymphocytes from 31 patients exposed to various organophosphate pesticides were examined for chromosomal aberrations (Van Bao et al. 1974). Five of the patients were exposed to methyl parathion only. Blood samples were taken 3-6 days after exposure and again at 30 and 180 days. A significant (p<0.05) increase was noted in the frequency of stable chromosomal aberrations in acutely intoxicated persons (although such cells are eventually lost from the cell population). Two of the methyl parathion-exposed persons had taken large doses orally in suicide attempts. The study limitations include small sample size, absence of a control group, lack of quantification of exposure levels, and possible... 

A recent method to screen the urine for alkyl phosphates as an indicator of exposure to organophosphate insecticides shows that the method can be used to determine environmental exposure to a specific organophosphate pesticide. The method was found to be sensitive, identifying low levels of exposure to insecticides in the environment by quantitation of urinary phosphates (Davies and Peterson 1997). The test is limited in that it is only useful for assessing recent exposure, due to the short half-life of the organophosphate pesticides. 

Cowart RP, Bonner FL, Epps EA Jr. 1971. Rate of hydrolysis of seven organophosphate pesticides. 

Davies JE, Peterson JC. 1997. Surveillance of occupational, accidental, and incidental exposure to organophosphate pesticides using urine alkyl phosphate and phenolic metabolite measurements. Aim NY Acad Sci 837 257-268. 

FosterRL. 1974. Detection and measurement of ambient organophosphate pesticides. ProcAnnuInd Air Pollut Control Conf 4 66-98. 

Nakagawa M, Uchiyama M. 1974. Effect of organophosphate pesticides on lecithin-cholesterol acyltransferase in human plasma. Biochem Pharmacol 23 1641-1645. 

Somara S, Siddavattam D. 1995. Plasmid mediated organophosphate pesticide degradation by Flavobactrium balustinum. Biochem Molec Biol Int 36 627-631. 

Fournier E. Sonnier, M, Dally S (1978) Detection and assay of organophosphate pesticides in human blood by gas chromatography. Clin Toxicol 12 457-462. 

The OPMBS was sponsored by a task force, consisting of major registrants of organophosphate pesticides, and utilized three contract organizations to carry out study management, design and conduct of sample collection, and quality assurance (QA). Four analytical laboratories performed the necessary residue analyses. 

In the OPMBS, all compounds were determined that occurred in the tolerance expression for organophosphate pesticides being supported by the registrants in each of the 13 commodities. Thus, compounds to be determined were those that might occur as residues of organophosphate pesticides whose continued use was supported by members of the OPMBS Task Force. 

Organophosphate Pesticides Revised OP Cumulative Risk Assessment USEPA, Washington, DC (2002). Also available ontheWorld Wide Web http //www.epa.gov/pesticides/cumulative/ rra-op/, accessed September 2002. 

The purpose of this chapter is not to discuss the merits, or lack thereof, of using plasma cholinesterase inhibition as an adverse effect in quantitative risk assessments for chlorpyrifos or other organophosphate pesticides. A number of regulatory agencies consider the inhibition of plasma cholinesterase to be an indicator of exposure, not of toxicity. The U.S. Environmental Protection Agency, at this point, continues to use this effect as the basis for calculating the reference doses for chlorpyrifos, and it is thus used here for assessing risks. 

Chemicals degraded by WRF include pesticides such as organochlorines DDT and its very toxic metabolite DDE [8, 9] and organophosphate pesticides such as chlorpyrifos, fonofos and terbufos [10] polychlorinated biphenyls (PCBs) of different degrees of chlorine substitution [11-13], some even to mineralization [14, 15] diverse polycyclic aromatic hydrocarbons (PAHs) in liquid media and from contaminated soils or in complex mixtures such as creosote [16-18] components of munition wastes including TNT and its metabolites DNT [19-23], nitroglycerin [24] and RDX [25]. 

Enzymes can be used not only for the determination of substrates but also for the analysis of enzyme inhibitors. In this type of sensors the response of the detectable species will decrease in the presence of the analyte. The inhibitor may affect the vmax or KM values. Competitive inhibitors, which bind to the same active site than the substrate, will increase the KM value, reflected by a change on the slope of the Lineweaver-Burke plot but will not change vmax. Non-competitive inhibitors, i.e. those that bind to another site of the protein, do not affect KM but produce a decrease in vmax. For instance, the acetylcholinesterase enzyme is inhibited by carbamate and organophosphate pesticides and has been widely used for the development of optical fiber sensors for these compounds based on different chemical transduction schemes (hydrolysis of a colored substrate, pH changes). 

Janotta M., Karlowatz M., Vogt F., Mizaikoff B., Sol-gel based mid-infrared evanescent wave sensors for detection of organophosphate pesticides in aqueous solution, Anal. Chim. Acta 2003 496 339-348. 

A. Mulchandani, W. Chen, P. Mulchandani, J. Wang, and K.R. Rogers, Biosensors for direct determination of organophosphate pesticides. Biosens. Bioelectron. 16, 225-230 (2001). 

S. Ozaki, H. Nakagawa, K. Fukuda, S. Asakura, H. Kiuchi, T. Shigemori, and S. Takahashi, Re-activation of an amperometric organophosphate pesticide biosensor by 2-pyridinealdoxime methochloride. Sens. 

K.A. Law and S.PJ. Higson, Sonochemically fabricated acetylcholinesterase micro-electrode arrays within a flow injection analyser for the determination of organophosphate pesticides. Biosens. Bioelectron. 20, 1914-1924 (2005). 

A. Vakurov, C.E. Simpson, C.L. Daly, T.D. Gibson, and P.A. Millner, Acetylcholinesterase-based biosensor electrodes for organophosphate pesticide detection I. Modification of carbon surface for immobilization of acetylcholinesterase. Biosens. Bioelectron. 20, 1118-1125 (2004). 

R.P. Deo, J. Wang, I. Block, A. Mulchandani, K.A. Joshi, M. Trojaowicz, F. Scholz, W. Chen, and Y. Lin, Determination of organophosphate pesticides at a carbon nanotube/organophosphorus hydrolase electrochemical biosensor. Anal. Chim. Acta 530, 185—189 (2005). 

The following factors have been suggested as alternatives to consider when presented with a potential case of exposure to nerve agents carbamate and organophosphate pesticides alkaloids such as nicotine or coniine ingestion of mushrooms containing muscarine and... 

Freed, V.H., C.T. Chiou, and D.W. Schmedding. 1979. Degradation of selected organophosphate pesticides in water and soil. Jour. Agric. Food Chem. 27 706. 

Allison, D.T. 1977. Use of Exposure Units for Estimating Aquatic Toxicity of Organophosphate Pesticides. 

McLean, S., M. Sameshina, T. Katayama, J. Iwata, C.E. Olney, and K.L. Simpson. 1984. A rapid method to determine microsomal metabolism of organophosphate pesticides. Bull. Japan. Soc. Sci. Fish. 50 1419-1423. 

Powell, G.V.N. and D.C. Gray. 1980. Dosing free-living nestling starlings with an organophosphate pesticide, famphur. Jour. Wildl. Manage. 44 918-921. 

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