Department of Physical and Environmental Sciences, University of Toronto, Toronto, Ontario, M1C 1A4, Canada.
Department of Physical and Environmental Sciences, University of Toronto, Toronto, Ontario, M1C 1A4, Canada; Ontario Ministry of Environment, Conservation and Parks, Toronto, Ontario, M9P 3V6, Canada.
Chemosphere. 2018 Nov;210:1193-1206. doi: 10.1016/j.chemosphere.2018.07.070. Epub 2018 Jul 17.
Polychlorinated biphenyl (PCB) contamination has historically posed constraints on the recreational and commercial fishing industry in the Great Lakes. Empirical evidence suggests that PCB contamination represents a greater health risk from fish consumption than other legacy contaminants. The present study attempts a rigorous assessment of the spatio-temporal PCB trends in multiple species across the Canadian waters of the Great Lakes. We applied a Bayesian modelling framework, whereby we initially used dynamic linear models to delineate PCB levels and rates of change, while accounting for the role of fish length and lipid content as covariates. We then implemented Bayesian hierarchical modelling to evaluate the temporal PCB trends during the dreissenid pre- and post-invasion periods, as well as the variability among and within the water bodies of the Great Lakes system. Our analysis indicates that Lake Ontario is characterized by the highest PCB levels among nearly all of the fish species examined. Historically contaminated local areas, designated as Areas of Concern, and embayments receiving riverine inputs displayed higher concentrations within each of the water bodies examined. The general temporal trend across the Great Lakes was that the high PCB concentrations during the early 1970s followed a declining trajectory throughout the late 1980s/early 1990s, likely as a result of the reductions in industrial emissions and other management actions. Nonetheless, after the late 1990s/early 2000s, our analysis provided evidence of a decline in the rate at which PCB concentrations in fish were dropping, accompanied by a gradual establishment of species-specific, steady-state concentrations, around which there is considerable year-to-year variability. The overall trends indicate that reduced contaminant emissions have brought about distinct beneficial changes in fish PCB concentrations, but past historical contamination along with other external or internal stressors (e.g., invasive species, climate change) continue to modulate the current levels, thereby posing potential risks to humans through fish consumption.
多氯联苯（PCB）污染历来对大湖地区的娱乐和商业捕鱼业构成限制。实证证据表明，与其他遗留污染物相比，鱼类消费中的 PCB 污染代表着更大的健康风险。本研究试图严格评估加拿大大湖水域多种鱼类的时空 PCB 趋势。我们应用了贝叶斯建模框架，最初使用动态线性模型来描绘 PCB 水平和变化率，同时考虑了鱼长和脂质含量作为协变量的作用。然后，我们实施了贝叶斯层次模型来评估在双壳类动物入侵前后时期的时间 PCB 趋势，以及大湖系统内各个水体之间和内部的可变性。我们的分析表明，安大略湖是在所检查的几乎所有鱼类中 PCB 水平最高的湖泊。历史上受污染的当地地区，被指定为关注区，以及接收河流输入的港湾，在每个检查的水体中都显示出更高的浓度。大湖地区的总体时间趋势是，20 世纪 70 年代初期的高 PCB 浓度在整个 20 世纪 80 年代末/90 年代初呈下降趋势，这可能是由于工业排放减少和其他管理措施的结果。尽管如此，20 世纪 90 年代末/21 世纪初以后，我们的分析提供了证据表明鱼类中 PCB 浓度下降的速度下降，同时伴随着特定物种的稳定状态浓度逐渐建立，其中存在相当大的年际变异性。总体趋势表明，减少污染物排放带来了鱼类 PCB 浓度的明显有益变化，但过去的历史污染以及其他外部或内部胁迫因素（例如，入侵物种，气候变化）继续调节当前水平，从而通过鱼类消费对人类构成潜在风险。
