Harlequin Ducks (Histrionicus histrionicus) were adversely affected by the Exxon Valdez oil spill (EVOS) in Prince William Sound (PWS), Alaska, and some have suggested effects continue two decades later. We present an ecological risk assessment evaluating quantitatively whether PWS seaducks continue to be at-risk from polycyclic aromatic hydrocarbons (PAHs) in residual Exxon Valdez oil. Potential pathways for PAH exposures are identified for initially oiled and never-oiled reference sites. Some potential pathways are implausible (e.g., a seaduck excavating subsurface oil residues), whereas other pathways warrant quantification. We used data on PAH concentrations in PWS prey species, sediments, and seawater collected during 2001–2008 to develop a stochastic individual-based model projecting assimilated doses to seaducks. We simulated exposures to 500,000 individuals in each of eight age/gender classes, capturing the variability within a population of seaducks living in PWS. Doses to the maximum-exposed individuals are ∼400–4,000 times lower than chronic toxicity reference values established using USEPA protocols for sea- ducks. These exposures are so low that no individual-level effects are plausible, even within a simulated population that is orders-of-magnitude larger than exists in PWS. We conclude that toxicological risks to PWS seaducks from residual Exxon Valdez oil two decades later are essentially non-existent.

Harlequin Ducks ( Histrionicus histrionicus)受到阿拉斯加威廉王子湾 (PWS)的埃克森瓦尔迪兹石油泄漏 (EVOS) 的不利影响，有些人认为这种影响会在 20 年后继续存在。我们提出了一项生态风险评估，定量评估 PWS 海鸭是否继续面临埃克森瓦尔迪兹石油残留中多环芳烃 (PAH) 的风险。确定了最初上油和从未上油的参考点的 PAH 暴露的潜在途径。一些潜在的途径是难以置信的（例如，一只海鸭挖掘地下油渣），而其他途径需要量化。我们使用 2001 年至 2008 年期间收集的 PWS 猎物物种、沉积物和海水中 PAH 浓度的数据来开发一个基于个体的随机模型，预测海鸭的同化剂量。我们模拟了八个年龄/性别类别中每个类别的 500,000 个人的暴露情况，捕捉生活在 PWS 中的海鸭种群的变异性。最大暴露个体的剂量比使用 USEPA 协议为海鸭建立的慢性毒性参考值低约 400-4,000 倍。这些暴露是如此之低，以至于个人水平的影响是不合理的，即使在比 PWS 中存在的数量级大的模拟人群中也是如此。我们得出的结论是，残留对 PWS 海鸭的毒理学风险二十年后的埃克森瓦尔迪兹石油基本上不存在了。