Aldicarb study

Dierberg, F. E., Aldicarb Studies in Groundwaters from Citrus Groves in Indian River County, Florida, Florida Water Resources Research Center Publication Ho. 76, 1984. 

In this study, the preliminary findings showed that the HPLC/fluorescence data were in agreement for all 12 carbamates with HPLC/ESI-MS/MS for most of the nine fruits and vegetables at the 1.0 ng g fortification level. The recoveries were generally within 70-120% however, at the 1.0 ng g level in each commodity, HPLC/ESI-MS (single-stage MS) had difficulty with interferences for three out of the 12 carbamate pesticides (aldicarb sulfoxide, aldicarb sulfone, and 3-hydroxycarbofuran), which made quantification impossible for these three compounds. 

Three compounds marketed as insecticides have been widely studied in this regard, namely Aldicarb, Phorate, and Disulfoton [93,164,190]. 

Banks and Tyrrell (1985) studied the Cu -promoted decomposition of aldicarb in aqueous solution in the pH region 2.91-5.51. 2-Methyl-2-(methylthio)propionitrile and 2-methyl-2-(meth-ylthio)propanal formed at yields of 82 and 18%, respectively. 

Hansen, J.L. and Spiegel, M.H. Hydrolysis studies of aldicarb, aldicarb sulfoxide and aldicarb sulfone. Environ. Toxicol. Chem., 2(2) 147-153, 1983. 

Jones, R.E., Hansen, J.L., Romine, R.R., and Marquardt, T.E. Unsaturated zone studies of the degradation and movement of aldicarb and aldoxycarb residues, Environ. Toxicol Chem., 5 361-372, 1986. 

Nucleophilic cleavage, acid catalyzed hydrolysis, and oxidation of aldicarb in dilute solution were achieved in batch and/or column experiments using macroporous reactive ion exchange resins. As in solution, nucleophilic cleavage proceeds faster than acid catalyzed hydrolysis. The basis for pursuing study of the latter mechanism is discussed. 

The first objective has been accomplished by the development of an HPLC procedure as reported by Spalik et al. ( 5) and GC/NPD procedures developed by Lemley and Zhong ( ). The second and third objectives are being accomplished by fundamental solution studies and reactive ion exchange experiments conducted in parallel. Lemley and Zhong (7) determined recently the solution kinetics data for base hydrolysis of aldicarb and its oxidative metabolites at ppm concentrations and for acid hydrolysis of aldicarb sulfone. They have since ( ) reported similar results for ppb solutions of aldicarb and its metabolites. In addition, the effect on base hydrolysis of temperature and chlorination was studied and the effect of using actual well water as compared to distilled water was determined. Similar base hydrolysis data for carbofuran, methomyl and oxamyl will be presented in this work. 

Materials. Aldicarb standards were obtained from the United States Environmental Protection Agency (USEPA), Quality Assurance Section and from Union Carbide Corporation. Crystalline samples of carbofuran and 3-hydroxycarbofuran were supplied by the Agricultural Chemical Group of FMC Corporation. Reference standards of methomyl (99% pure) and oxamyl (99% pure) were obtained from USEPA. HPLC grade methanol was purchased from Burdick and Jackson, Inc. Methylene chloride used for bulk extractions of the carbamate pesticides in solution was recovered, distilled and reused. Analytical reagent grade chemicals and solvents were used in all experiments. Doubly distilled deionized water was used for solution rate studies. Deionized distilled water (DDW) was used for dilutions in reactive ion exchange experim ts., , ... 

The UK Pesticide Safety Directorate (PSD) has decided to use the TEF approach for assessment of combined risk from exposure to mixtures of acetyl cholinesterase inhibitors (organophosphate (OP) compounds and carbamates) (PSD 1999). Despite clear differences in the action of carbamates and OP compounds, the index compounds selected for all acetyl cholinesterase inhibitors were either aldicarb (carbamate) or chlorpyrifos (OP). The POD for determining relative potency was predetermined as the dose level that produced 20% inhibition of red blood cell cholinesterase in a 90-day dietary study in rats. 

The application of the above method to the syntheses of insecticides carbamates Carbofuran (entry 4, table 3-27) and Aldicarbe was briefly studied. Thus, Carbofuran was readily obtained in 79% yield from 1-chloroethyl benzofu-ranyl carbonate which was itself obtained in 89% yield from the corresponding hydroxy benzofuran. 

Aldicarb is readily absorbed from all routes of exposure. Oxidation reactions rapidly convert aldicarb to aldicarb sulfoxide, of which a small portion may then be slowly oxidized to aldicarb sulfone. Both the parent compound and its oxidized metabolites can be converted to their respective oximes and nitriles, which may ultimately be converted to aldehydes, acids, and alcohols. Animal studies have indicated aldicarb and its metabolites are distributed to many different tissues but no evidence of accumulation has been found. In the various tissues examined, aldicarb residues were not detected more than 5 days after exposure. The presence of aldicarb in fetal tissue indicates placental transfer in pregnant rats. Various aldicarb metabolites have been found in the milk of cows acutely treated with aldicarb. 

Animal studies have indicated the major route of excretion to be urinary with at least 80% of the original dose generally eliminated within 24 h. Aldicarb is excreted primarily as aldicarb sulfoxide and sulfoxide oxime the parent compound is excreted only in trace amounts. Biliary metabolites have been shown to undergo resorption and urinary excretion. 

Toxicity of organophosphates can be potentiated 15-20-fold in rats and mice by pretreatment with a metabolite of tri-O-cresylphosphate, CBDP (2-0-cresyl)-4H-l,3,2-benzodioxa-phosphorin-2-oxide), which is an irreversible inhibitor of CarbEs. In similar studies, tetraisopropylpyrophosphoramide (iso-OMPA), or mipafox, an organophosphate-irreversible inhibitor of CarbEs, potentiates three-to fivefold the toxicity of several OPs (soman, DFP, and methylparathion) and carbamates (carbofuran, aldicarb, propoxur, and carbaryl). Inhibition of CarbEs by CBDP, iso-OMPA, or mipafox pretreatment, particularly in plasma, liver, heart, brain, and skeletal muscles, is a major contributory factor in the potentiation of toxicity of organophosphates and carbamates. Thus, the toxicity of any drug, pesticide, or other type of agent that is normally detoxified by CarbEs, could be potentiated by pre-exposure to an organophosphorus or other carboxylesterase inhibitor. 

M. L. Dourson, L. K. Teuschler, P. R. Durkin and W. M. Stiteler, Categorical Regression of Toxicity Data A Case Study using Aldicarb, Regulatory Toxicology and Pharmacology, 25, 121-129 (1997). 

A laboratory study on mice found that there was little or no observed effect when water containing nitrates (-4.39) alone, aldicarb (1.13) alone, or atrazine (2.61) alone at groundwater MCL levels were consumed. When consumed together, however, in drinking water at the MCLs for groundwater, the mixture altered immune, endocrine, and nervous system parameters. I26... 

Farmer Farm Family Exposure. Last year, the U. S. Environmental Protection Agency warned women of childbearing age to avoid farm fields recently treated with the herbicide dinoseb because the chemical might cause birth defects. Another study, conducted by a team of medical scientists, found that Kansas farmers exposed to a widely-used corn and wheat herbicide for 20 days or more a year had a sixfold increase in a certain kind of lymph cancers compared to non-farmers. And a third study from Wisconsin noted possible immune-system suppression due to aldicarb exposure. 

Aldicarb. The insecticide/nematicide aldicarb and its mobile degradation products ("aldicarb residues ) reportedly have been found in the groundwaters of 13 states (2). In general, aldicarb residues were highest for wells sampled nearest the field application sites. The influence of soil differences on the pattern of aldicarb movement is well illustrated in a recent study (61-2). Potato fields in northeastern Florida were located on sandy soil underlain at 1-2 m by an impervious clay layer (61). Residues leached downward, then laterally, emerging into drainage ditches at concentrations of ca. 

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