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Effect-Based Screening Methods for Water Quality Characterization Will Augment Conventional Analyte-by-Analyte Chemical Methods in Research As Well As Regulatory Monitoring. Elizabeth Doyl,† Adam Biales,‡ Mike Focazio,*,§ Dale Griffin,§ Keith Loftin,∥ and Vicki Wilson† †
United States Environmental Protection Agency, Washington, DC 20460, United States National Exposure Research Library, Washington, DC 20024, United States § Toxic Substances Hydrology Program, United States Geological Survey, Reston, Virginia 20192, United States ∥ Organic Geochemistry Research Laboratory, United States Geological Survey, Reston, Virginia 20192, United States need to analyze for the presence of thousands of chemical contaminants potentially present. Screening approaches drawing on rapidly evolving technologies, in association with modeling, will likely lead to new paradigms in assessing chemicals, mixtures of chemicals, and/or the potential for biological effect of water samples. The obvious benefit lies in the ability of these screening techniques to provide information about water chemistry and the potential for biological effect not obtainable with conventional approaches, some at a rapid rate with high sample throughput. However, interpretation of these results in terms of biological effects of contaminants and how this information may be used in regulatory or policy activities is still being developed. Importantly, conventional analyte-by-analyte approaches will continue to be essential components of water-quality investigations due to their high degree of specificity in targeting specific contaminants or contaminant groups. This level of specificity is required to provide data to manage and mitigate contaminant sources and understand contaminant behavior in the environment. ‡
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EFFECT-BASED SCREENING Effect-based assays are common and frequently used in the medical field in drug development. These assays provide information used to target the effects of drugs and to understand the potential for unintended side effects. Contaminants rarely occur alone in the environment or drinking water sources and by targeting key biological pathways, effectbased assays could provide early warning of the potential biological threats associated with unknown mixtures of contaminants. Relative to a conventional analytical chemistry approach, effect-based assays may have an advantage in their ability to indicate effects of the total sum of all chemicals acting along a particular pathway. For example, Whole Effluent Toxicity (WET) tests have been used to evaluate the adverse effects of unknown contaminant mixtures in effluents since the 1980s. In this sense we are defining effects broadly to include adverse outcomes as well as other indications of biological response such as gene regulation etc. Environmental researchers have been adapting this general approach for a variety of applications. The newer technologies include a range of assays indicative of a broad array of biological responses such
BACKGROUND Conventional approaches to water quality characterization can provide data on individual chemical components of each water sample. This analyte-by-analyte approach currently serves many useful research and compliance monitoring needs. However, these approaches, which require a priori targeting of a specific analyte or analytes, have fundamental and substantial limitations in accounting for the “universe” of millions of chemicals that could be present (see Feature Article in this issue). Over the past decade, the National Research Council and the EPA’s Science Advisory board have highlighted the need for the EPA to develop multichemical approaches to evaluate risk from chemical exposure. They have also recommended that the EPA develop risk assessments for chemicals grouped by adverse outcome rather than chemical structure for chemical exposure risk evaluation and assessment. Recently developed techniques that provide indications of the potential for a biological effect, chemical mass or structure, and other approaches that do not rely on analyte-by-analyte analyses have risen to the forefront of research on water quality characterization1,2. More comprehensive assays capable of screening samples for multiple biological pathways would provide a powerful tool for evaluating water quality without the © XXXX American Chemical Society
Received: November 10, 2014
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dx.doi.org/10.1021/es5053254 | Environ. Sci. Technol. XXXX, XXX, XXX−XXX
Environmental Science & Technology
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as gene regulation, molecular methods for identifying the presence of indicator organisms and pathogenic microorganisms, enzyme inhibition, and other approaches which do not necessarily indicate an adverse biological effect but are useful as biological screening tools. In this sense we define “effectsbased” assays to be inclusive of this broad array of screening approaches regardless of whether the assay indicates an actual adverse impact or not. An important next step in the application of effect-based methods in water quality research and management is developing the ability to quantify the activation of assay systems, and linking the activation to a threshold for an associated adverse outcome. To this end, validated, whole system receptor-based (all receptors crucial to life and quality of life), species-specific assays of environmental relevance (e.g., using salmon receptors when studying salmon, human receptors when studying humans) are needed as companions to “omics” and conventional methods to further identify, mechanistically isolate, regulate, and mitigate undesired effects. Surrogate receptors (e.g., mouse in place of human) must still be used in the interim until we can fully realize this speciesspecific capability in the future.
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AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS The views expressed in this article are those of the authors and do not necessarily represent the views or policies of the U.S. Environmental Protection Agency.
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REFERENCES
(1) Ferrer, I.; Thurman, E. M. Analysis of 100 pharmaceuticals and their degradates in water samples by liquid chromatography/ quadropole time-of-flight mass spectrometry. J. Chromatogr. 2012, 1259, 148−157. (2) Eckman, D. R.; Ankley, G. T.; Blazer, V. S.; Collette, T. W.; Garcia-Reyero, N.; Iwanowicz, L. R.; Jorgenson, Z. G.; Lee, K. E.; Mazik, P. M.; Miller, D. H.; Perkins, E. J.; Smith, E. T.; Tietge, J. E.; Villeneuve, D. L. Biological effects-based tools for monitoring impacted surface waters in the Great Lakes: A multiagency program in support of the Great Lakes Restoration Initiative. Environ. Pract. 2013, 15 (4), f1−f6.
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INTEGRATION OF EFFECT- AND CHEMICALLY BASED SCREENING RESEARCH NEEDED Chemically based screening provides the context for chemically induced adverse outcomes measured by effects-based screening assays by identifying the causative chemicals of an effect, relating an effect back to the chemical source, and describing the fate and transport between the source and the effect (e.g., the receptor). In addition, chemically based screening techniques will provide information about likely structures, mass, and other characteristics of contaminants in a water sample without the need for analyte-by-analyte approaches. Though chemical- and effect-based approaches are fundamentally similar screening tools, chemical-based approaches have their own strengths and limitations. As scientists continue to understand those limitations and build on the strengths of these approaches there will be a need for weight-of-evidence based research that combines chemically- and effects- based screening methods with conventional analyte-by-analyte monitoring. Thus, conventional techniques in combination with chemically based screening techniques will continue to be critical components of the broader water quality monitoring goals related to adverse outcome mitigation. These combined approaches and integration of chemical and effects-based data sets will augment one another providing deeper understanding of environmental contaminants and the effects they induce and will elucidate the appropriate uses of each approach alone or in combination for a variety of practical, and economically expedient monitoring applications. In conclusion, as effect-based monitoring continues to evolve, and research and development continues, conventional approaches will continue to be used as a component of compliance monitoring applications in the near term. They will permit continuity in implementation, while research and development activities move forward for the newer methods. Conventional methods will also provide a basis for comparison and validation of results from effect-based tools to facilitate implementation of new effect-based methods and provide information required to manage specific sources of contaminants. B
dx.doi.org/10.1021/es5053254 | Environ. Sci. Technol. XXXX, XXX, XXX−XXX
