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Pathway-based approaches for assessing biological hazards of complex mixtures of contaminants: A case study in the Maumee River
Citation:
Ankley, G., J. Berninger, B. Blackwell, J. Cavallin, Tim Collette, D. Ekman, K. Fay, D. Feifarek, K. Jensen, M. Kahl, J. Mosley, S. Poole, E. Randolph, D. Rearick, A. Schroeder, J. Swintek, AND Dan Villeneuve. Pathway-based approaches for assessing biological hazards of complex mixtures of contaminants: A case study in the Maumee River. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY. Society of Environmental Toxicology and Chemistry, Pensacola, FL, 40(4):1098–1122, (2021). https://doi.org/10.1002/etc.4949
Impact/Purpose:
The Maumee River and associated tributaries are an example of a system influenced by a mosaic of contaminant inputs from point and nonpoint sources along a gradient of land uses. To assess the potential effects of contaminants on aquatic biota in a system this complex requires a combination of targeted and nontargeted analytical and biological monitoring techniques to provide data that can be assembled and interpreted in an integrated manner. The aim of the current paper was to provide a practical demonstration of this type of approach using a variety of state-of-the-science pathway-based tools. Studies conducted in 2012 and 2106 showed that contaminants in the upper part of the Maumee River reflect agricultural practices, while downstream, the suite of chemicals present includes those from agriculture in conjunction with contaminants more indicative of a general urban setting, influenced in some areas by WWTP inputs. Biological responses using in vitro assays with surface water samples, and measures of biological responses in caged fish deployed a various sites in the Maumee River were used to assess the potential for perturbation of specific biological pathways. Overall there was little evidence for contaminant effects on endocrine pathways involved is reproduction or development. However, multiple lines of evidence suggested the presence of contaminants that could inhibit or induce cytochrome P450-based enzymes thereby influencing biological pathways/processes associated with these ubiquitous proteins.
Description:
Assessment of the ecological risks of chemicals at many field sites involves complex mixtures of known and unknown compounds. In recent years there has been substantial progress in the development of databases and tools that enable the integration of chemical and biological methods for complex mixture assessment based on observed or potential perturbation of different biological pathways. Herein we describe the application of pathway-based approaches to assessment of chemical mixtures in the Maumee River (OH, USA), which is potentially impacted by a variety of agricultural and urban inputs. Fathead minnows (Pimephales promelas) were deployed in cages for 4 d at a gradient of sites along the river and adjoining tributaries in 2012 and during two periods (April, June) in 2016, in conjunction with automated systems to collect corresponding composite water samples. More than 100 industrial chemicals, pharmaceuticals and pesticides were detected in water at some of the study sites, with the greatest number of chemicals typically found near domestic wastewater treatment plants. In 2016, there was a notable increase in concentrations of several herbicides from April to June at upstream agricultural sites. Comparison of chemical concentrations in those reported to cause effects in in vitro high-throughput testing (HTT) assays suggested the potential for perturbation of multiple biological pathways, including several associated with induction or inhibition of different cytochrome P450 (CYP) isozymes. This observation was consistent with the direct effects of composite water extracts in an HTT assay and the induction of hepatic CYPs in caged fish. Targeted in vitro assays and measurements in the caged fish suggested little in terms of effects on endocrine function (e.g., estrogenicity) at any site or sampling time. A nontargeted mass spectroscopy-based analysis of livers from the caged fish from 2016 suggested that endogenous metabolote profiles covaried primarily with the occurrence of pesticides. Overall, these studies demonstrate how application of an integrated suite of analytical and biological measurements can enhance understanding of the effects of complex chemical mixtures in a multi-faceted field setting.
URLs/Downloads:
DOI: Pathway-based approaches for assessing biological hazards of complex mixtures of contaminants: A case study in the Maumee River