You are here:
A Tiered Assessment Framework for Ecological Risk Assessment of Unknown or Variable Composition, Complex Reaction Products, or Biological Materials (UVCBs) (SETAC)
Citation:
Deglin, S., M. Fernandez, S. Hughes, C. Phillips, A. Williams, AND M. Embry. A Tiered Assessment Framework for Ecological Risk Assessment of Unknown or Variable Composition, Complex Reaction Products, or Biological Materials (UVCBs) (SETAC). SETAC Asia-Pacific, Online, NC, September 05 - 08, 2022. https://doi.org/10.23645/epacomptox.20468808
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 Unknown or Variable Composition, Complex Reaction Products, or Biological Materials (UVCBs) usually result from the industrial processing or extraction of natural substances or from chemical reactions. Because of the nature of source materials, and the potential variability inherent to production processes, these substances can contain many, sometimes uncharacterized constituents, in varying concentrations, affecting the ability to characterize substance identity and assess properties relevant to ecological risk assessment such as physical-chemical properties, environment fate and toxicity. As a result, UVCB/MCS risk assessment 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 an exposure-based tiered approach considering the minimum level of information required to perform a robust ecological risk assessment. The first step (Tier 0) considers basic and readily available substance characterization and exposure information. Characterization information includes substance specifications, quality assurance data, and basic chromatographic or elemental data, while exposure information includes use/importation volumes and end uses. Tier 0 information is evaluated to determine whether more characterization data might be needed for a preliminary assessment. This first tier is critical to allow the streamlined screening of UVCBs which may or may not need in-depth characterization. This framework was tested through the development of three case studies (Cedar Oil, Alkyl Dimethyl Benzyl Ammonium Chlorides, and Hydrogenated Resin Glycerol Ester), which revealed characterization of substance complexity and biodegradation as key steps. Substance complexity, defined as the combination of variability in constituent concentrations, diversity of constituent chemistries and chemical properties, and belonging to the applicability domain of existing test models, is likely to determine the needed depth of substance characterization. Also critical is the determination of when biodegradation should be evaluated, and whether it should be measured on the whole substance or its representative structures. This approach, which is expected to ensure that efforts and resources deployed for UVCBs risk assessment match actual needs and help streamline the risk assessment process, will be presented and discussed, including the evaluation of substance complexity, biodegradability, and associated challenges. This abstract does not necessarily represent the views or policies of the U.S. Environmental Protection Agency or CEFAS.
URLs/Downloads:
DOI: A Tiered Assessment Framework for Ecological Risk Assessment of Unknown or Variable Composition, Complex Reaction Products, or Biological Materials (UVCBs) (SETAC)
UVCB PRESENTATION - SETAC AP.PDF (PDF, NA pp, 1827.948 KB, about PDF)