Organophosphorus chemical specific

Methods for Determining Biomarkers of Exposure and Effect. Section 2.6.1 reported on biomarkers used to identify or quantify exposure to diazinon. Some methods for the detection of the parent compound in biological samples were described above. The parent chemical is quickly metabolized so the determination of metabolites can also serve as biomarkers of exposure. The most specific biomarkers will be those metabolites related to 2-isopropyl-6-methyl-4-hydroxypyrimidine. A method for this compound and 2-(r-hydroxy-l -methyl)-ethyl-6-methyl-4-hydroxypyrimidine in dog urine has been described by Lawrence and Iverson (1975) with reported sensitivities in the sub-ppm range. Other metabolites most commonly detected are 0,0-diethylphosphate and 0,0-diethylphosphorothioate, although these compounds are not specific for diazinon as they also arise from other diethylphosphates and phosphorothioates (Drevenkar et al. 1993 Kudzin et al. 1991 Mount 1984 Reid and Watts 1981 Vasilic et al. 1993). Another less specific marker of exposure is erythrocyte acetyl cholinesterase, an enzyme inhibited by insecticidal organophosphorus compounds (see Chapter 2). Methods for the diazinon-specific hydroxypyrimidines should be updated and validated for human samples. Rapid, simple, and specific methods should be sought to make assays readily available to the clinician. Studies that relate the exposure concentration of diazinon to the concentrations of these specific biomarkers in blood or urine would provide a basis for the interpretation of such biomarker data. 

Although several chemicals, e.g. arsenicals and organophosphorus compounds, had been used with some effect to treat specific helminth infections, the introduction in 1930 of phenothiazine (1) was a revolutionary event in the control of gastrointestinal worms. Although its spectrum of activity was narrow compared to modern anthelmintics and its dose level was rather high (600-800 mg kg-1), it was the veterinary anthelmintic of choice until the 1960s. 

P=0 Thomas and Chittenden (5,38 441 have carried out a thorough series of studies on the identification of organophosphorus compounds. The group frequency tables in these studies enable interpretation of many of the characteristic features in the spectra of nerve agents and related chemicals. Several structure-spectrum relationships give specific information on the molecule. One very valuable relation discovered by Thomas is the dependence of the position of the P=0 bond stretching vibration, vp=0, on the substituents on the phosphorus, represented by n constants ... 

Reactive chemicals enhance toxicity in relation to reactions with chemical structures found in biomolecules (e.g., epoxides) or to metabolism into more toxic compounds [65], Toxicity of specifically acting chemicals has turned out to be due to their interactions with certain receptors such as inhibition of acetylcholinesterase by organophosphorus compounds [65], A survey of the... 

The environmental significance of organic sulfoxides results primarily from their importance as agrochemicals specifically, the organophosphorus and carbamate insecticides containing sulfoxide moieties. Studies suggest that reduction of these chemicals can be the primary pathway for their transformation in anoxic sediments. For example, reduction of phorate sulfoxide to phorate in anoxic pond sediments occurred with half-lives ranging from 2 to 41 days (Equation 3.38) (Tratnyek and Wolfe, 1988). 

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