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Syntheticpolymerstypically have high molecular weights(5000e1000000 million u) and therefore their biological availabilityis negligible. However, due to the use of lower molecular
weight (<1000u) additives in these polymers as well as thepresence of trace levels of unreacted monomers, there isa finite potential for human exposure to these lower molecularweight components. （1）Substances that may migrate from plastic materials include monomers and startingsubstances, catalysts, solvents and additives.(2) This latter classincludes antioxidants, antistatics, antifogging agents, slip additives, plasticizers, heat stabilisers, dyes and pigments. 合成聚合物一般具有较高的分子量（5000--1000000U），因此他们的生物有效性是可以忽略的。然而，由于使用较低的分子重量（小于1000u）在这些聚合物添加剂以及微量未反应单体的存在，这是人类接触这些低分子量组分有限的潜力。可以从塑料材料中迁移的物质包括单体和起始物质、催化剂、溶剂和添加剂。这一类包括抗氧化剂、抗静电剂、防雾剂、滑剂、增塑剂、热稳定剂、染料和颜料。
（1）为原因状语从句，due to为介词短语，同样可以表示原因的短语有because of; thanks to; owing to等。
（2）that为关系代词， 引导定语从句，修饰substances。
Paper and boardare essentially composed of pulp fromdifferent vegetable sources and are most often employed incontact with dry foods. Additives used in this type of materialinclude fillers, starch and derivatives, wet strength sizingagents, retention aids, biocides, fluorescent whitening agentsand grease-proofing agents.（3） Paper and board may also becoated with polymers as polyethylene or waxes. Recycled fibre is considered a major source of migrants.（4）This route of contamination is officially recognised in the Resolution RESAP(2002)1 of the Council of Europe for paper and board in contact with foods, which lists DIPNs, benzophenone, partiallyhydrogenated terphenyls, solvents, phthalates, azo-colourants,primary aromatic amines and polycyclic aromatic hydrocarbons as being relevant.Corrugated board is most often used as transport packaging system and thus notanticipated to come into directcontact with food. （5）However, volatile substances in this typeof material used as a secondary package may be transferredthrough the primary packaging into the food .
（3）(5)（6）过去分词作定语，放在被修饰词后。
过去分词作定语，在语态上，表被动；在时间上，表示动作已经发生或完成，与它所修饰的名词有逻辑（意义）上的动宾关系。
过去分词作定语表示动作在谓语动作之前发生，已经完成并具有被动意义。
过去分词作定语既可以放在所修饰的词之前，作前置定语，也可以放在所修饰的词后面，作后置定语。表示被动和完成意义,其作用相当于一个定语从句。过去分词作后置定语可分为限制性（紧跟在所修饰的中心词之后）和非限制性（用逗号与其所修饰的中心词分开）两种，其作用分别相当于一个限制性定语从句和非限制性定语从句。如果被修饰的词是由every/some/any/no + thing/body/one所构成的复合代词或指示代词those等时，即使一个单一的分词作形容词用，也要放在被修饰词的后面。 过去分词作定语时与定语从句的关系：
(1) 及物动词的过去分词可改为动词为被动形式的定语从句。 lost time—time which is lost a well-known writer—a writer who is well- known a beaten team—a team which is beaten
(2) 部分不及物动词的过去分词作定语时可改为动词为完成式或动词为表示状态的定语从句。
a returned soldier-------a soldier who has returned retired workers------workers who have retired
a learned man—a man who is of much learning （4）为which引导的定语从句 which与that引导定语从句的区别
首先,that可指人和物,which则一般指物.,在限定性定语从句中两者的区别不大,但在非限定性定语从句中有以下区别： 一、以下情况不能用that,只能用which：1、在非限定性定语从句中,逗号之后不能用that；2、介词后面不能用that.
二、以下情况不能用which,只能用that：
1、前面的先行词是不定代词时,如 all ,anything ,nothing,the one 等； 2、如果先行词出现了the only ,the very 时；
3、如果先行词出现了序数词和形容词最高级时；
4、如果先行词中既有人又有物时,如：They are talking about the school and the teachers that they visited yesterday.
纸和纸板基本上是由不同的蔬菜来源的纸浆组成，最常接触干燥的食品。使用这种类型的材料的添加剂包括填料、淀粉及其衍生物、湿强度施胶剂、助留剂、杀菌剂、荧光增白剂、防油剂。纸和纸板也可作为聚乙烯或蜡的聚合物涂覆。再生纤维被认为是移民的主要来源。这条路线的污染都是官方承认的分辨率RESAP（2002）1接触食品的纸和纸板的欧洲议会，其中列出了dipns、苯甲酮、部分氢化三联苯，溶剂，邻苯二甲酸盐、偶氮染料、芳香胺、多环芳香族碳氢化合物作为相关。瓦楞纸板是最常被用作运输包装系统，因此没有被期望直接接触食品。然而，在这种类型的材料中，作为二次包装的挥发性物质可以通过主包装转移到食品。
Metal cansare made of tin-plate (steel coated with tin),tin-free steel (steel coated with chromium and chromiumoxides) or aluminium. Tin-plate is most used for foodcans and aluminium for beverage cans. Most cans are internally coated with a polymeric layer, and thus the layer offood contact is not the metal but the lacquer. The substances of concern in can systems are therefore not onlythe metals involved, but also components migrating fromthe coatings, such as starting substances and their potentialderivatives. Migrants from can coatings, namely phenolicresins, often contain only small amounts of monomers,oligomers and additives, but a large amount of otherunknown or undescribed components . 金属cansare采用马口铁（镀锡钢），无锡钢（涂有铬和铬的氧化物钢）或铝。锡板是最常用的食品罐和铝饮料罐。大多数罐在内部涂有聚合物层，因此，该层的食品接触不是金属，但漆。因此，可以系统的物质，因此不仅涉及的金属，但也从涂料中迁移的组件，如起始物质和它们的潜在的衍生物。移民可以涂层，即酚醛树脂，通常只含有少量的单体、低聚物和添加剂，但大量的其它未知或未描述的组件。
Glass packaginghas as its major components, silica,sodium and calcium oxides. These components are unlikelyto have any significant effect on the safety of foods since theyare natural constituents of many foods. Silica is also the major component of food-contactceramics. Clays, another major raw material of ceramics, is composed of alumina, silicaand water. Substances of concern may, however, originatefrom glazes and printing inks. Thus lead and cadmium arefrequently controlled in such materials since they may bepresent as contaminants. (6)The Food Standards Agency (UK)promoted a comprehensive overview of the potential for elemental migration from different glass types used in food-contact applications in a range of conditions of use.
玻璃包装为主要成分，二氧化硅，钠和钙的氧化物。这些成分是不可能有任何显着的影
响，因为它们是天然成分的食品安全的许多食物。硅也是食品接触陶瓷的主要成分。粘土，另一种主要的陶瓷原料，是由氧化铝、二氧化硅和水组成的。物质的关注，然而，来自釉和印刷油墨。因此，铅和镉经常被控制在这些材料中，因为它们可能存在的污染物。食品标准局（英国）促进了一个全面的概述，从不同的玻璃类型，在使用的条件下，使用在食品接触应用的元素迁移的潜力。
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2022-09-23
