Per- and polyfluoroalkyl substances along the St Louis River and in the Duluth, MN area 2019-2021

Tree swallow nest boxes were deployed at sites proximal to two putative aqueous film forming foam (AFFF) sources in the Duluth, MN area, as well as along the St. Louis River and a reference lake for comparative purposes. The two AFFF sites were the current Duluth Air National Guard Base (ANG) and the Lake Superior College Emergency Response Training Center. Concentrations of between 13 and 40 per- and polyfluoroalkyl substances (PFAS), depending on year, were quantified in tree swallow egg, nestling carcasses, and stomach contents. Assessments were made for oxidative stress and ethoxyresorufin-O-dealkylase biomarker responses in liver tissue, thyroid hormone levels in plasma and thyroid glands, DNA damage in red blood cells, and two measures of immune response (haptoglobin-like activity and immunoglobulin) in plasma of the nestlings. Additionally, other contaminants such as polychlorinated biphenyls, other legacy organochlorine pesticides, and trace elements were assessed at sites with no previous data. Total egg PFAS concentrations at the ANG site and north of there were 30 – 40 times higher than at the reference lake while nestling PFAS concentrations were 10 – 15 times higher than at the reference lake. In contrast, although the St. Louis River sites had slightly elevated egg and nestling PFAS concentrations relative to the reference lake (2 – 5 times higher), although those concentrations were not significantly higher. One PFAS, perfluorohexane sulfonate (PFHxS), was proportionately higher, as a proportion of total PFAS, at sites with a known AFFF source compared to the reference lake, but also compared to sites along the St. Louis River with mainly urban and industrial sources of PFAS. The ratio of total carboxylates to total sulfonates also distinguished between PFAS sources. There were few to no differences in biomarker responses among sites, and no association with PFAS exposure.

本研究在明尼苏达州德卢斯地区两处推定水成膜泡沫液（aqueous film forming foam, AFFF）污染源附近、圣路易斯河沿岸以及一处参照湖泊布设树燕巢箱，用于开展对比研究。两处AFFF污染源分别为当前运营的德卢斯空军国民警卫队基地（Duluth Air National Guard Base, ANG）与苏必利尔湖学院应急响应训练中心。
研究人员对树燕卵、雏鸟尸体及胃容物中的13至40种全氟和多氟烷基物质（per- and polyfluoroalkyl substances, PFAS）浓度进行了定量分析，具体数量因年份而异。同时针对雏鸟肝脏组织开展氧化应激与乙氧基试卤灵-O-脱烷基酶生物标志物响应评估，检测血浆与甲状腺中的甲状腺激素水平、红细胞DNA损伤情况，并测定血浆中两项免疫应答指标：结合珠蛋白样活性与免疫球蛋白。此外，研究还对此前无相关监测数据的点位开展了其他污染物检测，涵盖多氯联苯、其他持久性有机氯农药及微量元素。
德卢斯空军国民警卫队基地及其以北点位的卵PFAS总浓度为参照湖泊的30至40倍，雏鸟体内PFAS总浓度则为参照湖泊的10至15倍。与之形成对照的是，圣路易斯河沿岸点位的卵与雏鸟PFAS浓度虽较参照湖泊略有升高（为其2至5倍），但差异未达到统计学显著性水平。
与参照湖泊相比，已知AFFF污染源点位中，全氟己烷磺酸（perfluorohexane sulfonate, PFHxS）在总PFAS中的占比更高；同时相较于以城市与工业PFAS污染源为主的圣路易斯河沿岸点位，该占比同样更高。总羧酸盐与总磺酸盐的比值也可用于区分PFAS污染源类型。
各监测点位间的生物标志物响应差异极小，甚至无显著差异，且未观察到其与PFAS暴露存在关联。