Styrene was listed as “reasonably anticipated to be a human carcinogen” in the twelfth edition of the National Toxicology Program's Report on Carcinogens based on what we contend are erroneous findings of limited evidence of carcinogenicity in humans, sufficient evidence of carcinogenicity in experimental animals, and supporting mechanistic data. The epidemiology studies show no consistent increased incidence of, or mortality from, any type of cancer. In animal studies, increased incidence rates of mostly benign tumors have been observed only in certain strains of one species (mice) and at one tissue site (lung). The lack of concordance of tumor incidence and tumor type among animals (even within the same species) and humans indicates that there has been no particular cancer consistently observed among all available studies. The only plausible mechanism for styrene-induced carcinogenesis—a non-genotoxic mode of action that is specific to the mouse lung—is not relevant to humans. As a whole, the evidence does not support the characterization of styrene as “reasonably anticipated to be a human carcinogen,” and styrene should not be listed in the Report on Carcinogens.

在第十二版国家毒理学计划致癌物报告中，苯乙烯被列为“合理预期为人类致癌物”，这是基于我们认为对人类致癌性证据有限、对实验动物致癌性证据充分的错误发现，以及支持机械数据。流行病学研究表明，任何类型的癌症的发病率或死亡率均没有持续增加。在动物研究中，仅在一种物种（小鼠）和一种组织部位（肺）的某些品系中观察到大多数良性肿瘤的发病率增加。动物（即使在同一物种内）和人类之间肿瘤发病率和肿瘤类型缺乏一致性，这表明在所有现有研究中没有一致观察到特定的癌症。苯乙烯诱发致癌的唯一可能机制——一种针对小鼠肺部的非基因毒性作用模式——与人类无关。总体而言，证据并不支持将苯乙烯描述为“合理预期为人类致癌物”，并且苯乙烯不应被列入致癌物报告中。