School of Environmental Studies, Queen's University, Kingston, ON, Canada.
Institut national de la recherche scientifique (INRS), Centre Eau Terre Environnement, Quebec City, QC, Canada.
Environ Pollut. 2020 Nov;266(Pt 2):115165. doi: 10.1016/j.envpol.2020.115165. Epub 2020 Jul 9.
Ecological risk assessments (ERAs) of polycyclic aromatic compounds (PACs), as single congeners or in mixtures, present technical challenges that raise concerns about their accuracy and validity for Canadian environments. Of more than 100,000 possible PAC structures, the toxicity of fewer than 1% have been tested as individual compounds, limiting the assessment of complex mixtures. Because of the diversity in modes of PAC action, the additivity of mixtures cannot be assumed, and mixture compositions change rapidly with weathering. In vertebrates, PACs are rapidly oxygenated by cytochrome P450 enzymes, often to metabolites that are more toxic than the parent compound. The ability to predict the ecological fate, distribution and effects of PACs is limited by toxicity data derived from tests of a few responses with a limited array of test species, under optimal laboratory conditions. Although several models are available to predict PAC toxicity and rank species sensitivity, they were developed with data biased by test methods, and the reported toxicities of many PACs exceed their solubility limits. As a result, Canadian Environmental Quality Guidelines for a few individual PACs provide little support for ERAs of complex mixtures in emissions and at contaminated sites. These issues are illustrated by reviews of three case studies of PAC-contaminated sites relevant to Canadian ecosystems. Interactions among ecosystem characteristics, the behaviour, fate and distribution of PACs, and non-chemical stresses on PAC-exposed species prevented clear associations between cause and effect. The uncertainties of ERAs can only be reduced by estimating the toxicity of a wider array of PACs to species typical of Canada's diverse geography and environmental conditions. Improvements are needed to models that predict toxicity, and more field studies of contaminated sites in Canada are needed to understand the ecological effects of PAC mixtures.
多环芳烃 (PAC) 的生态风险评估 (ERA)，无论是作为单一同系物还是混合物，都存在技术挑战，这引起了人们对其在加拿大环境中准确性和有效性的关注。在超过 10 万种可能的 PAC 结构中，只有不到 1%的毒性作为单一化合物进行了测试，这限制了对复杂混合物的评估。由于 PAC 作用模式的多样性，不能假设混合物的加和性，并且混合物成分会随着风化而迅速变化。在脊椎动物中，PAC 会被细胞色素 P450 酶迅速氧化，通常会转化为比母体化合物毒性更大的代谢物。由于毒性数据来自对少数几种反应和有限的测试物种在最佳实验室条件下进行的测试，因此预测 PAC 的生态命运、分布和影响的能力受到限制。尽管有几种模型可用于预测 PAC 毒性和物种敏感性等级，但它们是使用测试方法存在偏差的数据开发的，并且许多 PAC 的报告毒性超过了它们的溶解度极限。因此，加拿大环境质量指南中针对几种个别 PAC 提供的信息很少，无法支持排放物和污染地点复杂混合物的 ERA。这三个 PAC 污染地点案例研究的综述说明了这些问题，这些案例研究与加拿大生态系统有关。生态系统特征、PAC 的行为、命运和分布以及 PAC 暴露物种的非化学压力之间的相互作用，使得 PAC 因果关系之间无法建立明确的联系。只有通过估计更广泛的 PAC 对加拿大多样化地理和环境条件下典型物种的毒性，才能降低 ERA 的不确定性。需要改进预测毒性的模型，并在加拿大污染地点进行更多的实地研究，以了解 PAC 混合物的生态影响。
