境中的化学组分.ppt

Chapter 3 Partition of Chemicals in environmental media 3.2 Estimation and modeling 1 Estimation of KH, KOW Basic Idea 目标化合物的某一活性是组成化合物分子的一个或n个碎片或二级结构对于某种活性的贡献或贡献之和，而同一碎片能作出的贡献在不同化合物中是相同的，与它所处的不同化合物无关。 理想的情况是，模型中的每一碎片与研究的活性之间有清楚的机理的关系，即在分子水平上基团或碎片对某种活性的贡献有明确的定量关系。但是目前尚无法实现。 从数学方法的角度看，（i）我们有足够量的一系列测量值（训练系列）可用于建造模型，（ii）可分辩一系列结构碎片与活性之间的关系，从而理性化地理解其作用。因此，采用基团贡献法，可以预测未知物质的构效关系。 HLC：Bond Contribution Method 通过大量已有的数据获得有机化合物的各种化学键对HLC的基本贡献值； 贡献值没有绝对的物理意义，但是相对值反映了不同化学键对化合物HLC的影响趋势； 提出一些设定值（人为定义值）； 规定一些基团在化学键中的表示方法。 2 Pollution Prevention (P2) Framework Models Overview Chemicals in Commerce Challenge: Evaluating Chemicals in the Absence of Data under TSCA EPA’s Approach to the Evaluation of New Chemicals in the Absence of Data Nearest analogue analysis (Are there data on a closely related structure?) Structure Activity Relationships (SAR) Cancer Expert System Computational approaches for estimating toxicity, fate, exposure from structure Physical / chemical properties Environmental fate Aquatic toxicity Exposure (general population, consumer, occupational, and aquatic, etc.) EPA’s P2 Framework EPA has automated many of the SARs, computational methods, expert systems, etc., used to predict hazard, exposure and associated risk, based on an analysis of structure and combined them into the P2 Framework. RD Process - Status Quo EPA Is Making the P2 Framework Available to Industry Models helped industry: Pre-screen chemical alternatives Understand potential risks of product alternatives under consideration at RD Understand potential risk trade-offs of alternatives under consideration Reduce product development costs Stimulate development of environmentally preferable products and processes P2 Framework Models Screening models: NOT replacing measured data! P2 Models predict information in 4 areas: Physical / chemical properties Environmental fate properties Hazard to humans and aquatic environment Exposure / risk Risk-related Information From P2 Framework Models Once rele