Van Zorge J A
Ministry of Housing, Spatial Planning and Environment, The Hague, The Netherlands.
Food Chem Toxicol. 1996 Nov-Dec;34(11-12):1033-6. doi: 10.1016/s0278-6915(97)00071-9.
The setting of standards for individual substances is an important tool in the protection of human health. However, it has been a topic of discussion for many years whether only this type of standard-setting will meet common goals for health protection, since humans are exposed to a large variety of chemical substances from many different sources in variable concentrations and by different routes of exposure. The complexity of this problem makes it difficult to answer this question and almost impossible to quantify the answer. It is common knowledge that combined exposure to chemical substances may cause synergism. However, these examples are referring to relatively high levels of exposure. In present environmental and occupational practice, exposure to individual chemicals has usually been reduced to acceptable levels. The key question is whether exposure to mixtures at levels of the single components near or below no-observed-adverse-effect levels can still cause adverse effects. Few countries have incorporated procedures concerning combination toxicity in their policy regarding chemical substances. If so, the uncertainty in these procedures is considerable because of lack of relevant data. This usually leads to a conservative approach. Roughly two approaches can be distinguished for systemic toxicants: introduction of an (extra) uncertainty factor or application of the additivity principle. In the Netherlands, for systemic toxicants a safety factor was introduced in 1989 to account for combination effects. Problems related to this approach have led to adaptations in procedures and a reconsideration of the chosen safety factor.
为个别物质设定标准是保护人类健康的一项重要手段。然而，多年来一直存在一个讨论话题，即仅靠这种标准设定方式是否能实现健康保护的共同目标，因为人类会通过多种不同途径、以不同浓度接触来自众多不同来源的大量化学物质。这个问题的复杂性使得难以回答，几乎不可能量化答案。众所周知，化学物质的联合接触可能会产生协同作用。然而，这些例子通常指的是相对较高的接触水平。在当前的环境和职业实践中，对单一化学品的接触通常已降至可接受水平。关键问题在于，在单一成分的接触水平接近或低于未观察到有害效应水平时，接触混合物是否仍会产生有害影响。很少有国家在其化学品政策中纳入有关联合毒性的程序。即便有，由于缺乏相关数据，这些程序中的不确定性也相当大。这通常会导致采取保守做法。对于全身毒性物质，大致可区分出两种方法：引入一个（额外的）不确定性系数或应用相加性原则。在荷兰，1989年针对全身毒性物质引入了一个安全系数，以考虑联合效应。与这种方法相关的问题促使程序进行了调整，并对所选安全系数进行了重新审视。
