Terrestrial toxicology data are limited for comprehensive ecotoxicological risk assessment of ecosystems contaminated by per- and polyfluoroalkyl substances (PFAS) partly because of their existence as mixtures in the environment. This complicates logistical dose–response modeling and establishment of a threshold value characterizing the chronic toxicity of PFAS to ecological receptors. We examined reproduction, growth, and survival endpoints using a combination of hypothesis testing and logistical dose–response modeling of northern bobwhite quail (Colinus virginianus) exposed to perfluorohexanoic acid (PFHxA) alone and to PFHxA in a binary mixture with perfluorooctane sulfonic acid (PFOS) via the drinking water. The exposure concentration chronic toxicity value (CTV) representative of the lowest-observable–adverse effect level (LOAEL) threshold for chronic oral PFAS toxicity (based on reduced offspring weight and growth rate) was 0.10 ng/mL for PFHxA and 0.06 ng/mL for a PFOS:PFHxA (2.7:1) mixture. These estimates corresponded to an adult LOAEL average daily intake CTV of 0.0149 and 0.0082 µg × kg body weight^–1 × d^–1, respectively. Neither no-observable–adverse effect level threshold and representative CTVs nor dose–response and predicted effective concentration values could be established for these 2 response variables. The findings indicate that a reaction(s) occurs among the individual PFAS components present in the mixture to alter the potential toxicity, demonstrating that mixture affects avian PFAS toxicity. Thus, chronic oral PFAS toxicity to avian receptors represented as the sum of the individual compound toxicities may not necessarily be the best method for assessing chronic mixture exposure risk at PFAS-contaminated sites. Environ Toxicol Chem 2021;40:2601–2614. © 2021 SETAC

中文翻译：

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暴露于全氟己酸 (PFHxA) 和全氟辛烷磺酸 (PFOS) 和 PFHxA 混合物的北方大白鹌鹑 (Colinus virginianus) 的慢性生殖毒性阈值

陆地毒理学数据在对被全氟和多氟烷基物质 (PFAS) 污染的生态系统进行全面的生态毒理学风险评估方面受到限制，部分原因是它们作为混合物存在于环境中。这使逻辑剂量反应模型和建立表征 PFAS 对生态受体的慢性毒性的阈值变得复杂。我们结合使用假设检验和北方鹌鹑 ( Colinus virginianus)的逻辑剂量反应模型来检查繁殖、生长和生存终点) 单独暴露于全氟己酸 (PFHxA) 和通过饮用水与全氟辛烷磺酸 (PFOS) 形成二元混合物的 PFHxA。代表慢性口服 PFAS 毒性的最低可观察不良反应水平 (LOAEL) 阈值的暴露浓度慢性毒性值 (CTV) 为 0.10 纳克/毫升，全氟己烷磺酸为 0.10 纳克/毫升，0.06 纳克/毫升对于 PFOS:PFHxA (2.7:1) 混合物。这些估计值对应于成人 LOAEL 平均每日摄入量 CTV 为 0.0149 和 0.0082 µg × kg 体重^–1  × d ^–1， 分别。对于这两个反应变量，既不能建立不可观察的不良反应水平阈值和代表性 CTV，也不能建立剂量反应和预测的有效浓度值。研究结果表明，混合物中存在的各个 PFAS 成分之间会发生反应以改变潜在毒性，这表明混合物会影响禽类 PFAS 毒性。因此，以单个化合物毒性总和表示的对禽类受体的慢性口服 PFAS 毒性可能不一定是评估 PFAS 污染地点慢性混合物暴露风险的最佳方法。环境毒物化学2021；40:2601–2614。© 2021 SETAC