Ecotoxicity: Methods, Challenges, and Findings in Assessing Ecological Effects of Nanocellulose

The increasing production and use of nanocellulose have raised concerns regarding their release into aquatic environments and associated ecological risks. This chapter reviews ecotoxicity research on cellulose nanofibrils (CNFs; also called cellulose nanofibers) and other nanocellulose, and summarizes key findings from the literature and the NEDO project. Previous studies indicate that CNFs exhibit low acute and chronic toxicity to aquatic organisms, including algae, crustaceans, and fish. However, growth inhibition has been reported in certain algal species at low concentrations under specific experimental conditions. Such variability is mainly attributed to differences in CNF physicochemical properties, production processes, dispersion stability, and test media composition, indicating the limited applicability of conventional guidelines to nanocellulose materials. To address these issues, CNF-specific analytical methods and ecotoxicity testing protocols were developed to ensure stable exposure conditions. Using these approaches, ecotoxicity tests were conducted on four representative CNF types. Most endpoints showed no adverse effects at concentrations up to 100 mg/L. Reduced reproduction of Daphnia magna was attributed primarily to decreased feeding efficiency rather than intrinsic CNF toxicity. Overall, ecological impact assessments indicate that the current ecological impact of CNFs in aquatic environments is low, while underscoring the need for additional chronic toxicity data.