Franklin James
CLF-Chem Consulting SPRL, Grez-Doiceau, Belgium.
Integr Environ Assess Manag. 2016 Jan;12(1):6-20. doi: 10.1002/ieam.1642. Epub 2015 Jun 16.
This review examines the usefulness of the metrics BMF (biomagnification factor) and TMF (trophic magnification factor), derived from field measurements of the levels of contaminants in naturally occurring biota, for characterizing the bioaccumulation potential ("B") of chemicals. Trophic magnification factor and BMF values greater than 1.0 are often considered to be the most conclusive indicators of B status, and the TMF criterion has been referred to as the "gold standard" for B categorization. Although not wishing to dispute the theoretical primacy of field-derived BMFs and TMFs as B metrics, we make the case that, in practice, the study-to-study (and even within-study) variability of the results is so great that they are of very restricted usefulness for assessing B status, at least in the case of the per- and polyfluoroalkyl substances (PFASs), on which we focus here. This conclusion is based on an analysis of the results of 24 peer-reviewed studies reporting field-derived BMFs or TMFs for 14 PFASs, for which BMF values often range over several orders of magnitude from <<1.0 to >>1.0, sometimes even in the same study. For TMFs, the range is a factor of approximately 20 for the most intensely studied PFASs (perfluorooctanoic acid [PFOA] and perfluorooctanesulfonic acid [PFOS]). We analyze the possible causes for such variability: To some extent it results from the differing ways in which the metrics are expressed, but most of the scatter is likely attributable to such factors as nonachievement of the tacitly assumed steady-state conditions, uncertainties in the feeding ecology, the impact of metabolism of precursor compounds, and so forth. As more trustworthy alternatives to field-derived BMFs and TMFs, we suggest the implementation of dietary BMF studies performed under strictly controlled conditions on aquatic, terrestrial, and avian species, as well as the consideration of measured elimination half-lives, which have been demonstrated to be directly related to BMF values.
本综述探讨了生物放大因子（BMF）和营养级放大因子（TMF）这两个指标的实用性，它们源自对天然生物群中污染物水平的实地测量，用于表征化学物质的生物累积潜力（“B”）。营养级放大因子和BMF值大于1.0通常被认为是B状态最具决定性的指标，TMF标准被称为B分类的“黄金标准”。尽管我们并不想质疑源自实地的BMF和TMF作为B指标的理论首要地位，但我们认为，在实际应用中，研究之间（甚至在同一研究中）结果的变异性非常大，以至于它们在评估B状态方面的实用性非常有限，至少在我们在此重点关注的全氟和多氟烷基物质（PFAS）方面是这样。这一结论基于对24项同行评审研究结果的分析，这些研究报告了14种PFAS的源自实地的BMF或TMF，其BMF值通常在几个数量级范围内变化，从远小于1.0到远大于1.0，有时甚至在同一研究中也是如此。对于TMF，在研究最深入的PFAS（全氟辛酸[PFOA]和全氟辛烷磺酸[PFOS]）中，范围约为20倍。我们分析了这种变异性的可能原因：在某种程度上，它源于指标表达方式的不同，但大部分离散可能归因于诸如未达到默认的稳态条件、摄食生态学中的不确定性、前体化合物代谢的影响等因素。作为源自实地的BMF和TMF更可靠的替代方法，我们建议对水生、陆地和鸟类物种在严格控制的条件下进行膳食BMF研究，并考虑测量的消除半衰期，已证明其与BMF值直接相关。
