Emerging investigator series: calculating size- and coating-dependent effect factors for silver nanoparticles to inform characterization factor development for usage in life cycle assessment

Abstract

Concerns about the environmental and human health implications of engineered nanomaterials (ENMs) are growing with the increased use in consumer and industrial products. Numerous studies have applied life cycle assessments (LCAs) to model the potential environmental and human health impacts of ENMs. Most of them have not included nano-specific emissions (i.e. impacts due to ENM release) and evaluated only non-nanoscale emissions (i.e. impacts due to ENM production). However, both considerations need to be included for more thorough evaluation of the environmental implications of these ENMs. One solution to calculate nano-specific emissions is to derive characterization factors (CF), which are comprised of information on fate, exposure, and effect factors for ENMs. This paper seeks to provide size, coating, and test medium dependent effect factors (EF) for silver nanoparticles (nAg), one of the most commercialized ENMs, using the USEtox model. A comprehensive literature review is performed, and 366 toxicity data points are used to derive physicochemical property based EFs. EFs are modeled based on different scenarios including species and trophic level HC₅₀ calculations under regular (using EC₅₀ values only) and cumulative (using LC₅₀, EC₅₀ and IC₅₀ values) cases. Different EFs are calculated based on varying size, coating, and testing medium combinations and presented in the form of matrices. Results suggest that larger nAg have lower EF, and coating is an important consideration in toxicity assessment. Regardless of specific properties, an EF range is proposed as 8035–14 675 PAF m³ kg⁻¹. Future work should combine fate and exposure factors to calculate CF for further application to LCA.