Farmer weed crop International Institute of Tropical Agriculture/Flickr

安全的物质怎样变得危险

帕洛阿尔托——自从16世纪毒理学诞生后,其指导原则一直是“剂量决定毒性。”这是每天都要在全球患者身上适用多达成百上千亿次的药理规则。恰当剂量的阿司匹林可以成为治病的天赐之物,但服用过量却可以致人死亡。该原则甚至适用于食品:高剂量的肉豆蔻甘草的毒性众所周知。

物质带来的广义风险取决于两大要素:其固有的伤害能力和人能否接触到它。这是个简单的理念,但就连某些假定的专业人士似乎也无法掌握——世卫组织下属的国际癌症研究机构(IARC)将常用的 2,4-D除草剂划为“可能的人类致癌物质”就是这方面的例证。

在除草剂的问题上,国际癌症研究机构似乎正在创造连败记录。该组织最近将另一种常用除草剂草甘膦也划归“可能的”致癌物质,这与世界各地监管机构的结论严重不符。

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