Introduction
Mitigating the impact of toxic chemicals on human health and the environment requires an informed transition to safer alternative chemicals, materials, and technologies. Alternatives assessment is a multi-disciplinary approach to support informed substitution and is defined as a “process for identifying and comparing potential chemical and non-chemical alternatives that could replace chemicals of concern on the basis of their hazards, performance, and economic viability” (National Research Council, 2014). To date, these approaches have been primarily used to support the transition to safer chemicals and processes. However, they were not designed to fully capture emerging chemicals/materials of concern, namely engineered nanomaterials (ENMs). Because ENMs offer superior functionality in a range of applications, they are now emerging (in development or commercially available) as replacements for functions currently being served by chemicals of concern. Examples include: • Multi-walled carbon nanotubes (MWCNTs) as replacements for halogenated flame retardants (Araby et al., 2021) • Nanowhiskers as a replacement for per- and polyfluroralkyl substances (PFAS) in stain resistant textiles and carpets (NanoTex, n.d.) • Organosilicates as replacements for PFAS surfactants in aqueous film forming foams (Davis, 2022) • Polymer nanocomposites as replacements for phthalate plasticizers (TDA Research, 2017) ENMs are demonstrating beneficial performance attributes, but a lack of guidance regarding how these materials should be assessed regarding their hazards and intrinsic exposure potential across their life cycles has stymied evaluations in alternatives assessment. The Sustainable Chemistry Catalyst at the University of Massachusetts Lowell was asked by the Washington State Department of Ecology to explore considerations for evaluating ENMs in the context of alternatives assessment processes. The first section of this White Paper provides an overview of key background concepts for thinking about ENMs, especially in comparison to conventional chemicals. The second section outlines considerations for addressing ENMs in alternatives assessments. These considerations were developed using the Interstate Chemicals Clearinghouse’s Alternatives Assessment Guide (Version 1.1) (IC2 Guide) as a alternatives assessment framework model using modules focused on: (a) identifying potential alternatives, (b) hazard assessment, (c) comparative exposure assessment, and (c) life cycle impacts. As such, these considerations for the evaluation of ENMs in alternatives assessment are also applicable to other guidance documents. APPENDIX I provides a detailed review of the literature pertaining to the evaluation of ENMs. Considerations for the evaluation of alternatives assessment were derived from this comprehensive literature review. Although placed in an appendix, this literature review outlines key methodological developments regarding the assessment of potential human and environmental impacts associated with ENMs. The review focuses on methodologies that are aligned with approaches used for alternatives assessments, including risk assessment and life cycle assessment. The review is recommended for any reader nee