Pesticides labeling

Fig. 8.6 Cumulative volatilization of " C-labeled pesticides and metabolites after soil surface application on Gleyic Cambisol. (after Wolters et al. 2003)...

Maibach and co-workers (18) have reported the percutaneous absorption of a number of pesticides using a technique they developed, in which 14C labelled pesticide is applied to the skin, and the total urine output is collected until all the radioactivity has been excreted. These data are corrected for incomplete excretion by using the excretion data obtained following intravenous or intramuscular injection. 

Atkins, D.H.R and Eggleton, A.E.J. 1971. Studies of atmospheric wash-out and deposition of A-BHC, dieldrin and p,p -DDT using radio-labelled pesticides, lnt. Atomic Energy Agency Symp., Vienna, SM-142a/32, pp. 521-533. 

Bioaccumulatlon of some pesticides (fenitrothion, aminocarb, permethrin) with real or potential application in forestry in Canada has been examined in laboratory experiments using larval rainbow trout and common duckweed. Bioaccumulation of an aromatic hydrocarbon, fluorene, has also been examined since some commercial formulations employ hydrocarbon solvents. Laboratory exposures of fish or plants were carried out by placing the organisms in dilute aqueous solutions of C labelled pesticide or hydrocarbon, and by measuring transfer of radioactivity from water to fish or plants. After transfer of fish or plants to untreated water, loss of radioactivity was measured similarly. These measures allowed calculation of uptake and depuration rate constants which were used to predict residue accumulations under various exposure conditions. Predicted residue accumulations agreed substantially with other predictive equations in the literature and with reported field observations. 

Finally, we have encountered situations where carbon-14 from a labeled pesticide has been incorporated into normal natural products including amino acids. We were interested in seeing if we could separate the normal amino acids from a protein hydrolysate on a single column with sufficient resolution to identify separate amino acids. Figure 11 shows a radiochromatogram of the separation of sixteen standard C-amino acids. Were this a product of a metabolism study, we could then isolate any of these fractions, convert the residual amino acid to the N-trifluoroacetyl 0-butyl derivative for gas chromatography ar.d further confirmation of structure. 

Figure 4. Distribution of [1 ]C—DDT in larval M. sexta hemolymph. 19 h after topical application, hemoTymph was subjected to density gradient ultracentrifugation as shown in Figure 3. Following centrifugation the tube was fractionated and the radioactivity in each fraction determined. Most of the labeled pesticide was found in the lipophorin fraction.

I. Scheunert, R. Schroll, G. Cao, A Microcosm System to Evaluate the Fate of C-labelled Pesticides in Soils from Different Climate Zones, in Proceedings of a Symposium Environmental Behavior of Crop Protection Chemicals. IAEA-SM-343/ 21, Vienna, Austria, 1997, pp. 18I-I86. 

J.-L. Wolfender, S. Rodriguez, K. Hostettmann, LC coupled to MS and NMR spectroscopy for the screening ofplant constituents, J. Chromatogr. A, 794 (1998) 299. D.M. Drexler, P.R. Tiller, S.M. Wilbert, F.W. Bramble, J.C. Schwartz, Automated identification of isotopically labeled pesticides and metabolites by intelligent real time LC-MS-MS using a bench-top ion trap MS, Rapid Commun. Mass Spectrom., 12 (1998) 1501. 

Xenobiotics are frequently metabolized in plants by mechanisms that lead to the incorporation or inclusion of the xenobiotic into biological polymers or tissue residues that are not soluble in commonly used nonreactive solvents. These residues are frequently refered to as bound, insoluble, or nonextractable residues (2 ). Bound residues in plants have most commonly been detected in plant tissues treated with radloactlvely-labeled pesticides. These residues were an important topic of a symposium held in Vail, Colo, in 1975 (17) they have been discussed in mauiy more recent papers (11,154-1577"and they were discussed at a symposium at the l88th ACS National Meeting, 1984 "Non-extractable Pesticide Residues Characteristics, Bioavailability and Toxicological Significance". 

Degradation Studies. Some laboratory studies on enhanced biodegradation have involved use of gas chromatographic analyses while lather studies have included measurement of CO2 resulting from C-labeled pesticide degradation to assess the severity of the problem, delineate the impact of environmental factors, or determine cross-adaptation Qi)- In our soil... 

Measurements of the incorporation of 14C-labeled pesticides tend to support the concept of limited microbial growth from pesticide degradation. In order for a pesticide to support support substantial growth, concomitant levels of mineralization and incorporation into biomass should be observed. Studies with 14C-2,4-D, labeled in either the acetic acid or ring structures show that more 14C from the acetic acid is incorporated into biomass than from ring-labeled, depending upon soil type and the time after addition of the 14C to the soil (Table 1). Even lower amounts of carbofuran were incorporated into biomass than were observed for 2,4-D. There was not a strong relationship between mineralization and incorporation into biomass. 

Kubiak, Maurer and Eichhom (1993) presented a new laboratory chamber constructed for studying the volatilization of " C-labeled pesticides from plant and soil surfaces. An air-conditioning system provides for temperature and relative humidity conditions between 10 °C and 30 °C and 35 % to 90 %, respectively. Wind speed simulation between... 

Although laboratory studies have value for specific purposes, it is in the natural ecosystem that we must determine the behavior of a pesticide and its possible effect. Studies of the cycling of radionuclide-labeled pesticides in natural ecosystems are limited, since introduction of radionuclides into the environment involves public-health and public-relations issues as well as possibly difficult technical considerations. However, an ecosystem study was conducted by spraying a 4-acre marsh in western Sandusky Bay, Ohio, with Cl-labeled DDT. One aspect of the study involved the incorporation of the pesticide in some invertebrates of this aquatic ecosystem as determined by autoradiography (Webster, 1967). An amount of the pesticide suitable for mosquito control was applied to the study area by helicopter. Samples of leeches (Erpobdella punctata), am-phipods (Hyallela sp.), and copepods (Cyclops bicuspidatus, Diaptomus orga-nensis) were collected, fixed, sectioned, and autoradiographed. It was observed that leeches contained the pesticide or a Cl-compound, but none was detected in amphipods or copepods. 

The pesticide lindane has been widely used in agriculture as a seed dressing. Using C-labeled lindane, Saha (1975) studied its biodegradation in plants and animals. He studied the residue distribution over time in chicks and eggs of pheasants fed the labeled pesticide in gelatin capsules. Pheasants were also fed treated wheat seeds. In addition, the occurrence of residue was determined in samples of brain, liver, breast muscle, and fat from five hen pheasants. 

Directed Public Health Sawice to provide grants for industrial waste studies and construction of treatment works Restricted sale and distribution of pesticides aU pesticides must be registeed with USEPA and be propCTly labeled pesticide may have no advCTse effect on the environment when properly used... 

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