U.S. Fish and Wildlife Service, 2651 Coolidge Road, Suite 101, East Lansing, Michigan 48823, USA.
Environ Toxicol Chem. 2010 Jul;29(7):1581-92. doi: 10.1002/etc.195.
Chlorinated hydrocarbon concentrations in eggs of fish-eating birds from contaminated environments such as the Great Lakes of North America tend to be highly intercorrelated, making it difficult to elucidate mechanisms causing reproductive impairment, and to ascribe cause to specific chemicals. An information- theoretic approach was used on data from 197 salvaged bald eagle (Haliaeetus leucocephalus) eggs (159 clutches) that failed to hatch in Michigan and Ohio, USA (1986-2000). Contaminant levels declined over time while eggshell thickness increased, and by 2000 was at pre-1946 levels. The number of occupied territories and productivity increased during 1981 to 2004. For both the entire dataset and a subset of nests along the Great Lakes shoreline, polychlorinated biphenyls (SigmaPCBs, fresh wet wt) were generally included in the most parsimonious models (lowest-Akaike's information criterion [AICs]) describing productivity, with significant declines in productivity observed above 26 microg/g SigmaPCBs (fresh wet wt). Of 73 eggs with a visible embryo, eight (11%) were abnormal, including three with skewed bills, but they were not associated with known teratogens, including SigmaPCBs. Eggs with visible embryos had greater concentrations of all measured contaminants than eggs without visible embryos; the most parsimonious models describing the presence of visible embryos incorporated dieldrin equivalents and dichlorodiphenyldichloroethylene (DDE). There were significant negative correlations between eggshell thickness and all contaminants, with SigmaPCBs included in the most parsimonious models. There were, however, no relationships between productivity and eggshell thickness or Ratcliffe's index. The SigmaPCBs and DDE were negatively associated with nest success of bald eagles in the Great Lakes watersheds, but the mechanism does not appear to be via shell quality effects, at least at current contaminant levels, while it is not clear what other mechanisms were involved.
受污染环境（如北美的五大湖）中的食鱼鸟类的蛋中的氯化烃浓度往往高度相关，这使得难以阐明导致生殖障碍的机制，并将原因归咎于特定的化学物质。在密歇根州和俄亥俄州（1986-2000 年）未能孵化的 197 枚白头海雕（Haliaeetus leucocephalus）蛋（159 窝）的数据上，使用了一种信息论方法。随着时间的推移，污染物水平下降，蛋壳厚度增加，到 2000 年已达到 1946 年之前的水平。1981 年至 2004 年，占区数量和生产力增加。对于整个数据集和五大湖沿岸的巢子集，多氯联苯（ΣPCBs，新鲜湿重）通常被包括在描述生产力的最简约模型（最低 Akaike 信息准则 [AIC]）中，在 ΣPCBs（新鲜湿重）超过 26μg/g 时观察到生产力显著下降。在 73 枚有可见胚胎的蛋中，有 8 枚（11%）异常，包括 3 枚喙歪斜，但它们与包括 ΣPCBs 在内的已知致畸原无关。有可见胚胎的蛋中所有测量污染物的浓度均高于无可见胚胎的蛋；描述有可见胚胎存在的最简约模型纳入了狄氏剂当量和二氯二苯二氯乙烯（DDE）。蛋壳厚度与所有污染物之间存在显著的负相关，ΣPCBs 被纳入最简约模型。然而，生产力与蛋壳厚度或 Ratcliffe 指数之间没有关系。ΣPCBs 和 DDE 与五大湖流域白头鹰的巢成功率呈负相关，但在当前污染物水平下，机制似乎不是通过蛋壳质量的影响，而目前尚不清楚还涉及哪些其他机制。
