有毒污染物指的是进入生物体后累积到一定数量能使体液和组织发生生化和生理功能的变化，引起暂时或持久的病理状态，甚至危及生命的物质。如重金属和难分解的有机污染物等。污染物的毒性与摄入机体内的数量有密切关系。同一污染物的毒性也与它的存在形态有密切关系。价态或形态不同，其毒性可以有很大的差异。如Cr（Ⅵ）的毒性比Cr（Ⅲ）大；As（Ⅲ）的毒性比As（Ⅴ）大；甲基汞的毒性比无机汞大得多。另外污染物的毒性还与若干综合效应有密切关系。从传统毒理学来看，有毒污染物对生物的综合效应有三种：⑴相加作用，即两种以上毒物共存时，其总效果大致是各成分效果之和。⑵协同作用，即两种以上毒物共存时，一种成分能促进另一种成分毒性急剧增加。如铜、锌共存时，其毒性为它们单独存在时的8倍。⑶拮抗作用，两种以上的毒物共存时，其毒性可以抵消一部分或大部分。如锌可以抑制镉的毒性；又如在一定条件下硒对汞能产生拮抗作用。总之，除考虑有毒污染物的含量外，还须考虑它的存在形态和综合效应，这样才能全面深入地了解污染物对水质及人体健康的影响。
Toxic pollutants refer to substances that accumulate to a certain amount after entering organisms, which can change the biochemical and physiological functions of body fluids and tissues, cause temporary or lasting pathological state, and even endanger life. Such as heavy metals and refractory organic pollutants. The toxicity of pollutants is closely related to the amount of pollutants taken into the body. The toxicity of the same pollutant is also closely related to its existing form. The toxicity can vary greatly with the valence or morphology. For example, the toxicity of chromium (VI) is greater than that of chromium (III); the toxicity of As (III) is greater than that of As (V); and the toxicity of methylmercury is much greater than that of inorganic mercury. In addition, the toxicity of pollutants is closely related to some comprehensive effects. From the point of view of traditional toxicology, there are three kinds of comprehensive effects of toxic pollutants on organisms: (1) additive effect, that is, shusongdaid.07858.net shusongdaie.07858.net shusongdaig.07858.netshiyanjii.07858.net juanlianji.07858.net falan.71ix.comwhen more than two kinds of toxicants coexist, the total effect is roughly the sum of the effects of each component. (2) Synergism, that is, when more than two toxicants coexist, one component can promote the toxicity of another component to increase sharply. When copper and zinc coexist, their toxicity is 8 times as high as that when they exist alone. (3) Antagonism. When more than two kinds of poisons coexist, their toxicity can offset part or most of them. For example, zinc can inhibit the toxicity of cadmium, and selenium can antagonize mercury under certain conditions. In a word, besides the content of toxic pollutants, the existing forms and comprehensive effects of toxic pollutants should also be considered, so as to fully and thoroughly understand the impact of pollutants on water quality and human health.