Research

Developing a strategy to improve the environmental risk assessment of substances of unknown and variable composition (MCS/ UVCB)

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Abstract

The complexity of Multi-Constituent Substances (MCS) and Substances of Unknown or Variable Composition, Complex Reaction Products, and Biological Materials (UVCBs) pose a unique challenge to regulators and to product registrants having to characterize their fate, exposure, hazard, and potential risks to human health and the environment. International regulatory frameworks (specifically REACH, Canada’s DSL Categorization and Chemicals Management Plan, and USEPA’s PMN process) have highlighted the difficulties of registering these products. A new HESI Project Committee was started in early 2018, with the goal of developing a tiered approach to assess ecological risks of MCS / UVCB to address scientific and regulatory needs. Through the engagement of stakeholders facing challenges associated with these substances, this Committee will foster the exchange of knowledge about MCS / UVCB, and develop and optimize a cross-sectorial approach for the classification, identification, characterization and assessment of these substances. In first step, the Committee focused on the mapping of the vast and complex universe of UVCB substances to provide a foundation for subsequent work, and better understand the nature of these substances and their sector(s) of use. It will also provide insight on which groups of substances present the largest regulatory challenges and where strategic approaches for assessment would be most valuable. The outcome of the mapping exercise will also inform how to apply existing analytical assessment methods such as read-across, QSAR and trend analysis to characterize UVCBs and evaluate their potential hazard. It may also allow for the identification of analytical gaps and inform the development of new UVCB identification and characterization methods. Finally, part of this effort will be devoted to the review and evaluation of existing sector-specific MCS / UVCB assessment tools with an aim towards making them more widely applicable to other substances and/ or to develop new assessment tools and methods that apply to other substance groups. Ultimately, this project will lead to the development of best practices to appropriately evaluate the environmental fate, and assess the ecotoxicity of MCSs / UVCBs.