铀和钍是重金属，它们的所有同位素都具有放射性，因此不可能完全独立地研究化学效应。在这项研究中，我们试图比较两种金属的化学和放射毒性，考虑到急性放射病和慢性健康损害（例如肿瘤诱发）所反映的确定性辐射损伤和随机辐射损伤。我们首先对可能由化学效应引起的急性中位致死剂量进行了文献搜索，因为即使作为急性放射毒性的表现，急性放射病也存在潜伏期。通过基于国际放射防护委员会的生物动力学模型和使用集成生物分析模块软件的模拟，我们确定了不同浓缩等级的铀和钍-232的量，导致短期红骨髓相当剂量为3.5 Sv，被认为可导致50％的人类死亡率。考虑了不同的摄入途径和与化学毒性的平均致死剂量进行了比较。为了评估随机辐射毒性，我们计算了导致承诺有效剂量为200 mSv的铀和钍的量，这通常被认为是关键的。铀和钍的平均致死值处于相同数量级，因此数据不支持急性化学毒性存在显着差异的观点。在比较放射毒性时，必须考虑参考单位（以Bq或g为活度或重量）。红骨髓的平均致死剂量相当于3.5 Sv的铀活度比钍的活度低。然而，对于铀和钍-232，只有摄入超过化学毒性的平均致死剂量的数量才会导致急性放射病。因此，急性放射病对于任何一种金属都不是一个相关的临床问题。关于随机辐射损伤，如果摄入相同的活度，钍-232比铀更具辐射毒性。使用重量单位进行比较表明，对于可溶性化合物，当摄入时，钍-232比低浓缩铀更具辐射毒性，但在吸入或静脉注射后，钍-232比高浓缩铀更具毒性。对于不可溶性化合物，情况则不同，钍-232的随机辐射毒性范围在贫化和自然铀之间。对于急性效应，即使在高浓缩等级下，铀的化学毒性以及钍-232超过确定性放射毒性。模拟表明，以活度单位表示，钍-232比铀更具辐射毒性。如果比较基于重量单位，则排名取决于铀的浓缩等级和摄入途径。©2023. 作者。

Uranium and thorium are heavy metals, and all of their isotopes are radioactive, so it is impossible to study chemical effects entirely independent of the radiation effects. In the present study, we tried to compare the chemo- and radiotoxicity of both metals, taking into account deterministic radiation damages reflected by acute radiation sickness and stochastic radiation damages leading to long-term health impairments (e.g., tumor induction). We made at first a literature search on acute median lethal doses that may be expected to be caused by chemical effects, as even acute radiation sickness as a manifestation of acute radiotoxicity occurs with latency. By simulations based on the biokinetic models of the International Commission on Radiological Protection and using the Integrated Modules for Bioassay Analysis software, we determined the amounts of uranium at different enrichment grades and thorium-232 leading to a short-term red bone marrow equivalent dose of 3.5 Sv considered to cause 50% lethality in humans. Different intake pathways for incorporation were considered, and values were compared to the mean lethal doses by chemotoxicity. To assess stochastic radiotoxicity, we calculated the uranium and thorium amounts leading to a committed effective dose of 200 mSv that is often considered critical. Mean lethal values for uranium and thorium are in the same order of magnitude so that the data do not give evidence for substantial differences in acute chemical toxicity. When comparing radiotoxicity, the reference units (activity in Bq or weight in g) must always be taken into account. The mean lethal equivalent dose to the red bone marrow of 3.5 Sv is reached by lower activities of thorium compared to uranium in soluble compounds. However, for uranium as well as thorium-232, acute radiation sickness is expected only after incorporation of amounts exceeding the mean lethal doses by chemotoxicity. Thus, acute radiation sickness is not a relevant clinical issue for either metal. Concerning stochastic radiation damages, thorium-232 is more radiotoxic than uranium if incorporating the same activities. Using weight units for comparison show that for soluble compounds, thorium-232 is more radiotoxic than low-enriched uranium in the case of ingestion but even more toxic than high-enriched uranium after inhalation or intravenous administration. For insoluble compounds, the situation differs as the stochastic radiotoxicity of thorium-232 ranges between depleted and natural uranium. For acute effects, the chemotoxicity of uranium, even at high enrichment grades, as well as thorium-232 exceeds deterministic radiotoxicity. Simulations show that thorium-232 is more radiotoxic than uranium expressed in activity units. If the comparison is based on weight units, the rankings depend on the uranium enrichment grades and the route of intake.© 2023. The Author(s).