通常人们所说的毒物是一些能导致人急性中毒并产生严重症状的物质。其实毒物不只这些、按现代毒理学观点来看,某种物质是否具有毒性主要取决于其摄入量。所以,通常认为没有毒的一些物质,如氧气在大量摄入后,就会成为毒物了。将两种不同剂量的致癌物注入动物体内,一种引起癌症,另一种则不引起。如何确定对人引起癌症的剂量呢?在美国,认为人是对毒物反应最敏感的,所以在确定接触极限值时,都带有20％至1000％ Often people call poisonous substances that can cause acute poisoning and cause serious symptoms. In fact, not only poison these, according to modern toxicology point of view, whether a substance is toxic depends mainly on its intake. Therefore, some substances that are generally considered non-toxic, such as oxygen, become toxic when consumed in large amounts. Two different doses of carcinogens are injected into animals, one causing cancer and the other not causing it. How to determine the dose of cancer causing cancer? In the United States, people are considered the most sensitive to toxic reactions, so in determining the exposure limit, with 20% to 1000%