Sandermann Heinrich
GSF - National Research Centre for Environment and Health, Institute for Biochemical Plant Pathology, D-85764 Neuherberg, Germany.
Pest Manag Sci. 2004 Jul;60(7):613-23. doi: 10.1002/ps.888.
Plants are well known to incorporate pesticides into bound and unextractable residues that resist solubilization in common laboratory solvents and are therefore not accessible to standard residue analysis. A characterization of such residues has been proposed for incorporation rates above trigger values of 0.05 mg kg(-1) parent pesticide equivalents, or percentage values of 10% (United States Environmental Protection Agency, 1995) or 25% (Commission of the European Communities, 1997) of the total radioactive residue. These trigger values are often exceeded. The present review describes the current status of the chemical characterization and animal bioavailability of bound and unextractable residues that may be xenobiotic in nature or result from natural recycling of simple degradation products. The latter case represents a mechanism of detoxification. Bound residues have been shown to be covalent or non-covalent in nature. With regard to the plant matrix molecules involved, incorporation into proteins, lignins, pectins, hemicelluloses and cutins has been demonstrated, and four covalent linkage types are known. Animal feeding experiments have revealed cases of low as well as high bioavailability. Many of the studies are limited by experimental uncertainties and by results only being reported as relative percentage values rather than absolute exposure. A preliminary value of absolute exposure from bound and unextractable residues is derived here for the first time from eight case studies. The mean exposure (ca 1.5 mg kg(-1) pesticidal equivalents) exceeds some of the existing maximum residue levels (MRLs) of residual free pesticides that are typically in the range of 0.05-1 mg kg(-1). A mathematical framework for the correction of current maximum residue levels is presented for cases of highly bioavailable bound residues. As bound pesticidal residues in food plants could represent a source of significant consumer exposure, an experimental test scheme is proposed here. It consists of basic chemical characterization, model digestibility tests and, in exceptional cases, animal bioavailability and additional toxicological studies.
众所周知，植物会将农药纳入结合态和不可提取的残留物中，这些残留物在常见实验室溶剂中难以溶解，因此无法通过标准残留物分析进行检测。对于结合态残留物的特性描述，是在母体农药当量的掺入率超过触发值0.05 mg kg⁻¹，或总放射性残留物的10%（美国环境保护局，1995年）或25%（欧洲共同体委员会，1997年）的百分比值时进行的。这些触发值经常被超过。本综述描述了结合态和不可提取残留物的化学特性及动物生物利用度的现状，这些残留物可能本质上是外源性的，或者是简单降解产物自然循环的结果。后一种情况代表了一种解毒机制。结合态残留物已被证明本质上是共价或非共价的。关于所涉及的植物基质分子，已证明农药会掺入蛋白质、木质素、果胶、半纤维素和角质中，并且已知有四种共价连接类型。动物喂养实验揭示了生物利用度低和高的情况。许多研究受到实验不确定性的限制，而且结果仅以相对百分比值报告，而非绝对暴露量。这里首次从八个案例研究中得出结合态和不可提取残留物的绝对暴露初步值。平均暴露量（约1.5 mg kg⁻¹农药当量）超过了一些残留游离农药的现有最大残留限量（MRLs），这些限量通常在0.05 - 1 mg kg⁻¹范围内。针对生物利用度高的结合态残留物情况，提出了一个校正当前最大残留限量的数学框架。由于食用植物中的结合态农药残留可能是消费者大量暴露的一个来源，这里提出了一个实验测试方案。它包括基本化学特性分析、模型消化率测试，以及在特殊情况下的动物生物利用度和额外的毒理学研究。
