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A tiered assessment framework for UVCB Ecological Risk Assessment
Citation:
Deglin, S., C. Di Paolo, M. Embry, C. Phillips, G. Thouand, AND A. Williams. A tiered assessment framework for UVCB Ecological Risk Assessment. SETAC EU, Copenhagen, N/A, DENMARK, May 15 - 19, 2022. https://doi.org/10.23645/epacomptox.20261313
Impact/Purpose:
The US-EPA Center for Computational Toxicology and Exposure (CCTE) has been generating data and building software applications and web-based chemistry databases for over a decade. To support our efforts to develop new approaches to prioritize chemicals based on potential human health risks, we aggregate and curate data streams of various types to support prediction models. DSSTox currently stands as the most comprehensive registry of chemical substances available in ORD. However, due to the complexity of description required to document UVCBs and nanomaterials, these have been registered in the most generic way by embedding the key attributes into free-text descriptions. Product encompasses conceptualization and development of new methods for representing mixtures and complex substances, such as UVCBs, nanomaterials, and environmental samples, as well as designing the means to support locally managed curation needs. UVCB chemicals (including polymers, mixtures, and isomer groups) are not only an important component of EPA chemical lists (e.g. TSCA, Pesticide Inerts), but many other research areas could benefit from standardized structure-linked representations of UVCB substances. The results of these efforts will be of direct benefit to program and regional offices as well as the greater scientific community.
Description:
Complex substances such as multi-constituent substances (MCS), and substances of Unknown or Variable Composition, Complex Reaction Products, and Biological Materials (UVCBs) usually result from the industrial processing or extraction of natural substances, or from chemical reactions. Because of the nature of UVCB/MCS source materials, and the potential variability inherent to their production processes, these substances can contain many, sometimes uncharacterized, constituents, whose concentration may vary. As a result, the risk assessment of UVCB/MCS presents unique challenges to product registrants and regulators alike. To address these challenges, the UVCB Committee of the Health and Environmental Sciences Institute is building a fit-for-purpose, exposure-based tiered approach relying on the minimum level of information required to perform a robust and fit-for-purpose ecological risk assessment. The first step of this approach (Tier 0) relies on basic and readily available characterization and exposure information. For example, Tier 0 substance characterization information includes substance specifications, QA data, and basic chromatographic and/or elemental analyses, and Tier 0 exposure data include use/importation volumes, and end uses. Tier 0 information is then used to perform a preliminary assessment, and determine whether more characterization information might be needed. This first tier of the assessment is critical to allow the rapid screening of UVCBs which may not need in-depth characterization. The framework was tested through the development of three case studies (Cedar Oil, ADBACs, and Hydrogenated Resin Glycerol Ester). The exercise revealed various obstacles and gaps, which need to be addressed to facilitate this new approach. One determining factor in the tiering of the risk assessment, is the level of complexity of the substance of interest, since the level of characterization is likely to increase with complexity. Substance complexity was defined as the combination of three characteristics, namely: variability in constituent concentrations, diversity of chemistries and chemical properties of constituents, and belonging to the applicability domain of existing test models. Another critical part of the assessment is the characterization of substance biodegradation. When should biodegradation be evaluated? Should it be measured on the whole substance or representative structures? This approach is expected to ensure that the efforts and resources deployed for UVCBs risk assessment match actual needs, and help streamline the risk assessment process. The tiered risk assessment framework and how it can provide the necessary information for a reliable assessment will be presented. The different steps of the approach will be illustrated, including the important evaluation of substance complexity, and the evaluation of substance biodegradability and associated challenges will be discussed. This abstract does not necessarily represent the views or policies of the U.S. Environmental Protection Agency.
URLs/Downloads:
DOI: A tiered assessment framework for UVCB Ecological Risk Assessment
UVCB POSTER_SETAC COPENHAGEN_MAY 2022_V2.PDF (PDF, NA pp, 496.375 KB, about PDF)