Several exposure limits for perchlorate have been developed based on an early key event, inhibition of radioactive iodide uptake (RAIU) by the thyroid. These assessments have used a variety of definitions of the point of departure. The current assessment revisited the modeling for inhibition of RAIU, using state of the science methods. Bayesian hierarchical modeling was used to account for the repeated measures on the same individuals in the key dataset, and the underlying Beta distribution used for the modeling correctly reflected the bounding of RAIU between 0 and 1. We defined the BMR as a point value of 8% RAIU (rather than a change in RAIU), based on descriptions in the medical literature that RAIU below this value is considered abnormal. Because a definition of the BMR based on the mean response would correspond to about 50% of the population with a response below the BMR at the benchmark dose, we used a hybrid definition of the BMR. That is, the BMD was defined as the dose at which it was estimated that there would be a 10% extra risk in the population of having RAIU of 8% or lower. The resulting point of departure based on the BMDL was 0.03 mg/kg-day.

中文翻译：

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更新的 BMD 建模方法对人类健康危害的高氯酸盐和氯酸盐评估的影响

基于早期的关键事件，即甲状腺对放射性碘摄取 (RAIU) 的抑制，已经制定了若干高氯酸盐暴露限值。这些评估使用了各种出发点的定义。当前的评估使用科学方法的状态重新审视了抑制 RAIU 的模型。贝叶斯分层建模用于解释关键数据集中相同个体的重复测量，用于建模的基础 Beta 分布正确反映了 RAIU 在 0 和 1 之间的边界。我们将 BMR 定义为点值为 8 % RAIU（而不是 RAIU 的变化），基于医学文献中的描述，即 RAIU 低于此值被认为是异常的。因为基于平均反应的 BMR 定义对应于大约 50% 的人群的反应低于基准剂量的 BMR，所以我们使用了 BMR 的混合定义。也就是说，BMD 被定义为估计在 RAIU 为 8% 或更低的人群中将有 10% 额外风险的剂量。根据 BMDL 得出的出发点为 0.03 mg/kg-day。