Environmental risk assessment and testing of UVCBs through balanced consideration of whole substances and representative constituent data: a tripartite perspective

Complex substances such as multi-constituent substances 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 variable and complex nature of source materials and the potential variability inherent to production processes, these substances can contain many, sometimes uncharacterized, constituents whose concentrations may vary between production batches. UVCBs make up approximately 20-25% of substances registered under regulatory frameworks globally. To identify and advance the various challenges associated with UVCB testing and assessment, the Health and Environmental Sciences Institute (HESI) organized an international workshop on Exploring the complexities of UVCB testing and risk assessment. The HESI UVCB workshop was aimed at initiating multi-sectoral, tripartite discussions on the advantages and disadvantages of the whole substance vs. representative constituent testing and assessment approaches, at identifying further research needs, and at establishing potential consensus for solutions for UVCB environmental risk assessment. Ultimately, the insight from the workshop contributed to the further refinement and strengthening of the exposure-centric tiered approach developed previously for consideration in the environmental risk assessment of UVCBs and multi-constituent substances. More specifically, it contributed to developing a systematic process to efficiently balance the characterization and testing of the whole substance and representative constituents to ensure the assessment of UVCBs is fit for purpose.