Scientific concepts and methods for moving persistence assessments into the 21st Century

Russell Davenport*, Pippa Curtis-Jackson, Philipp Dalkmann, Jordan Davies, Kathrin Fenner, Laurence Hand, Kathleen McDonough, Amelie Ott, Jose Julio Ortega-Calvo, John R. Parsons, Andreas Schäffer, Cyril Sweetlove, Stefan Trapp, Neil Wang, Aaron Redman

*Corresponding author for this work

Research output: Contribution to journalReviewpeer-review

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Abstract

The evaluation of a chemical substance's persistence is key to understanding its environmental fate, exposure concentration, and, ultimately, environmental risk. Traditional biodegradation test methods were developed many years ago for soluble, nonvolatile, single-constituent test substances, which do not represent the wide range of manufactured chemical substances. In addition, the Organisation for Economic Co-operation and Development (OECD) screening and simulation test methods do not fully reflect the environmental conditions into which substances are released and, therefore, estimates of chemical degradation half-lives can be very uncertain and may misrepresent real environmental processes. In this paper, we address the challenges and limitations facing current test methods and the scientific advances that are helping to both understand and provide solutions to them. Some of these advancements include the following: (1) robust methods that provide a deeper understanding of microbial composition, diversity, and abundance to ensure consistency and/or interpret variability between tests; (2) benchmarking tools and reference substances that aid in persistence evaluations through comparison against substances with well-quantified degradation profiles; (3) analytical methods that allow quantification for parent and metabolites at environmentally relevant concentrations, and inform on test substance bioavailability, biochemical pathways, rates of primary versus overall degradation, and rates of metabolite formation and decay; (4) modeling tools that predict the likelihood of microbial biotransformation, as well as biochemical pathways; and (5) modeling approaches that allow for derivation of more generally applicable biotransformation rate constants, by accounting for physical and/or chemical processes and test system design when evaluating test data. We also identify that, while such advancements could improve the certainty and accuracy of persistence assessments, the mechanisms and processes by which they are translated into regulatory practice and development of new OECD test guidelines need improving and accelerating. Where uncertainty remains, holistic weight of evidence approaches may be required to accurately assess the persistence of chemicals.
Original languageEnglish
JournalIntegrated Environmental Assessment and Management
Volume18
Issue number6
Pages (from-to)1454-1487
Number of pages34
ISSN1551-3777
DOIs
Publication statusPublished - 2022

Keywords

  • Biodegradation
  • Persistence assessment
  • Biodegradability
  • Bioavailability
  • Degradation half-lives

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