Pesticide toxicological characteristics

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". 

Polychlorinated biphenyls (PCB), while not pesticides, are chlorinated hydrocarbons. Many chemical and toxicological characteristics of PCB s are similar to those of the chlorinated hydrocarbon pesticides (2). PCB s are distributed widely, but their significance as residues has not been established. 

Technology providers use quantitative immunoassays to determine expression data of field material for regulatory submissions. Regulatory authorities require that expression levels of introduced proteins in various plant parts be determined by quantitative, validated methods. Immunoassays are also used to generate product characterization data, to assess food, feed and environmental characteristics, to calculate concentrations for toxicology studies and to obtain tolerance exemption or establish tolerances for pesticidal proteins. 

Selection criteria include toxicology, physical/chemical characteristics, and environmental fate information. These data are used to evaluate individual chemicals and estimate the degree of hazard associated with each site. For nonpoint source contamination from pesticide application, rating values include the amount of chemical applied. Final ranking is based on well logs, hydrogeology, and other data derived from on-site reconnaissance. 

Percutaneous absorption studies utilizing rhesus monkeys have one Important single advantage. That is, their skin type and absorption characteristics seem to be similar to humans. This is of utmost concern since the purpose of this study is to simulate the human case. This is not a toxicology study, and it should not be the purpose of this study to estimate a worst case scenario as in a hazard identification study. Thus, in spite of the many shortcomings of the described procedures, monkey percutaneous absorption studies could play an important role in pesticide risk assessments. 

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