Ecotoxicology & Wildlife Health Division, Science & Technology Branch, Environment and Climate Change Canada, Burlington, Ontario, Canada L7R 1A2.
Ecotoxicology & Wildlife Health Division, Science & Technology Branch, Environment and Climate Change Canada, Burlington, Ontario, Canada L7R 1A2.
Environ Res. 2019 Feb;169:464-475. doi: 10.1016/j.envres.2018.11.031. Epub 2018 Nov 22.
In the Canadian Athabasca Oil Sands Region (AOSR), nestling tree swallows (Tachycineta bicolor) raised near mining-related activities accumulated greater concentrations of polycyclic aromatic compounds (PACs) that contributed to their poorer condition, growth, and reproductive success. Here, we report changes in thyroid function of the same 14 day old (do) nestlings (N ≤ 68) at these mining-related sites (OS1, OS2) compared to reference nestlings (REF1), and in relation to multiple environmental stressors that influence avian thyroid function. Thyroid function was compromised for OS1 nestlings but generally comparable between OS2 and REF1 chicks. In 2012, circulating total triiodothyronine (TT3) and thyroxine (TT4) were similar among all nestlings. The OS1 chicks had more active thyroid glands based on histological endpoints. Hepatic T4 outer-ring deiodinase (T4-ORD) activity was suppressed in OS1 and OS2 chicks. Despite inter-annual differences, OS1 chicks continued experiencing compromised thyroid function with significantly higher circulating TT4 and more active thyroid glands in 2013. The OS2 chicks had less active thyroid glands, which conceivably contributed to their suppressed growth (previously reported) relative to the heavier OS1 nestlings with more active thyroid glands. Thyroid gland activity was more influenced by the chicks' accumulation of (muscle), than exposure (feces) to naphthalene, C2-naphthalenes, and C1-fluorenes. Of four major volatile organic contaminants, sulfur dioxide (SO) primarily influenced thyroid gland activity and structure, supporting previous findings with captive birds. When collectively considering environmental-thyroidal stressors, chicks had a greater thyroidal response when they experienced colder temperatures, accumulated more C2-naphthalenes, and consumed aquatic-emerging insects with higher PAC burdens than terrestrial insects (carbon (δC)). We hypothesize that the more active thyroid glands and higher circulating TT4 of the OS1 chicks supported their growth and survival despite having the highest PAC burdens, whereas the lack of thyroid response in the OS2 chicks combined with high PAC burdens, contributed to their smaller size, poorer condition and poorer survival.
在加拿大阿萨巴斯卡油砂区（AOSR），在与采矿相关的活动附近饲养的巢燕（Tachycineta bicolor）积累了更多的多环芳烃（PAC），这导致它们的状况、生长和繁殖成功率更差。在这里，我们报告了同一窝（OS1、OS2）和参考窝（REF1）14 天大的雏鸟的甲状腺功能变化，以及影响鸟类甲状腺功能的多种环境胁迫因素。OS1 雏鸟的甲状腺功能受损，但 OS2 雏鸟和 REF1 雏鸟的甲状腺功能基本相当。2012 年，所有雏鸟的循环总三碘甲状腺原氨酸（TT3）和甲状腺素（TT4）相似。OS1 雏鸟的甲状腺更活跃，基于组织学终点。OS1 和 OS2 雏鸟的肝外 T4 外环脱碘酶（T4-ORD）活性受到抑制。尽管存在年度差异，但 OS1 雏鸟在 2013 年继续经历甲状腺功能受损，其循环 TT4 显著升高，甲状腺更活跃。OS2 雏鸟的甲状腺活动较少，这可能导致其生长受到抑制（先前报道），而 OS1 雏鸟体重较重，甲状腺活动更活跃。甲状腺活动受雏鸟肌肉中（而非粪便中）萘、C2-萘和 C1-芴的积累影响大于暴露。在四种主要挥发性有机污染物中，二氧化硫（SO）主要影响甲状腺活动和结构，支持之前对笼养鸟类的研究。当综合考虑环境甲状腺应激源时，当雏鸟经历更冷的温度、积累更多的 C2-萘并食用水生昆虫时，它们的甲状腺反应更大，这些昆虫的多环芳烃（PAC）负荷比陆生昆虫（碳（δC））更高。我们假设，尽管 OS1 雏鸟的多环芳烃（PAC）负荷最高，但它们更活跃的甲状腺和更高的循环 TT4 支持它们的生长和生存，而 OS2 雏鸟缺乏甲状腺反应，加上高多环芳烃（PAC）负荷，导致它们体型更小，状况更差，生存能力更差。
